Displays

Operationalising nature-based solutions for mitigating hydro-meteorological hazards

 Prashant Kumar^1,*, Sisay Debele¹, Jeetendra Sahani¹, Silvana Di Sabatino²

 ¹Global Centre for Clean Air Research (GCARE), Department of Civil and Environmental Engineering, Faculty of Engineering and Physical Sciences, University of Surrey, Guildford GU2 7XH, United Kingdom

²Department of Physics and Astronomy, University of Bologna, Viale Berti Pichat 6/2, 40127, Bologna, Italy

^*Presenting author. Email: p.kumar@surrey.ac.uk

Abstract

The impact of weather- and climate-related hydro-meteorological hazards (HMHs) is amongst the greatest global challenges society is facing today. The concept of nature-based solution (NBS) is becoming popular for HMH management but the lack of knowledge on NBS designing and effectiveness is hindering its wider acceptance. This work discusses HMH risk analysis, relevant data, the role of NBS and its operationalisation by bringing co-design concept and testing them in OPERANDUM project’s open-air laboratories (OALs). HMH risk assessment employs different methodologies with respect to exposure, vulnerability and adaptation interaction of the elements at risk. The classification and effectiveness of any NBS depend on its location, design, typology and environmental conditions. OALs, via the collaboration of researchers and end-users, can foster increasing uptake, upscaling, replication and implementation of NBS projects as compared to traditional grey infrastructure approach. Multi-hazard risk analysis and inclusion of NBS into policy plans can foster NBS operationalisation processes across all sectors and at levels by fostering participatory processes such as co-design, co-creation and co-management among municipalities, researches, policy-makers, funding agencies and other stakeholders; and can inspire more effective use of skills, knowledge, manpower, as well as economic, social and cultural resources. NBS data monitoring, its standardisation, accessible storage and compliance with existing standard metadata is needed. The monitoring and evaluation manuals and guidelines are needed to decrease uncertainty about performance and overall cost-effectiveness of NBS and overcome potential hurdles to create long-term stability and enhance the wider uptake of NBS.   

Keywords: Hydro-meteorological hazards, nature-based solution, climate change, policy, co-design, co-creation, operationalisation 

Acknowledgements: This work is carried out under the framework of OPERANDUM (OPEn-air laboRAtories for Nature baseD solUtions to Manage hydro-meteo risks) project, which is funded by the Horizon 2020 under the Grant Agreement No: 776848. We thank OPERANDUM collaborators (Laura Leo, Francesca Barisanid, Bidroha Basu, Edoardo Bucchignani,  Nikos Charizopoulosg, Alessio Domeneghetti,  Albert Sorolla Edo, Leena Finér, Glauco Gallotti,  Sanne Juch, Michael Loupis, Slobodan B. Mickovski, Depy Panga, Irina Pavlova, Francesco Pilla, Adrian Löchner Prat, Fabrice G. Renaud, Martin Rutzinges,  Arunima Sarkar, Mohammad Aminur Rahman Shah, Katriina Soini, Maria Stefanopoulou, Elena Toth, Liisa Ukonmaanaho, Sasa Vranic, Thomas Zieher, for their contributions.

How to cite: Kumar, P., Debele, S., Sahani, J., and Di Sabatino, S.: Operationalising nature-based solutions for mitigating hydro-meteorological hazards, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17928, https://doi.org/10.5194/egusphere-egu2020-17928, 2020.

Nature-based solutions (NBS) are "inspired and supported by nature. They are cost-effective and simultaneously provide environmental, social and economic benefits and help build resilience" (EU, 2015). The main objective of the H2020 project PHUSICOS is to demonstrate the implementation of nature-based solutions to reduce the risk of extreme weather events in vulnerable areas such as rural mountain landscapes. To meet this aim, three large-scale demonstration sites have been selected in Tuscany, Italy, The Pyrenees, France/Spain and the Gudbrandsdalen Valley, Norway as representative of hydro-meteorological hazards, vegetation, topography and infrastructure throughout rural and mountainous regions in Europe. Additionally, two small-scale concept cases are established in Kaunertal Valley, Austria and the Isar River Basin, Germany to test specific challenges. This presentation focuses on the three large scale demonstrator sites.

PHUSICOS started in 2018 and over the four-year period each demonstrator site shall propose and implement at least three NBS projects each. At present 9 NBSs have been proposed.

The Italian proposals, organized by Autorità di Bacino Distrettuale, ADBS, relate to the pollution, drought, erosion, and land degradation around lake Massaciuccoli in Tuscany. The measures are related to reduce the runoff from farmland to the channels and the lake, as well as to reduce the high salinity of the lake. Proposed measures include feeding water from the Serchio River to the lake, and the establishment of vegetation buffer strips between the farmed land and the channels and retention basins.

In the Pyrenees, the proposed measures, organized by Consorcio de la Comunidad de Trabajo de los Pirineos, CTP, are to reduce risk from several hydrometeorological hazards; flooding and torrents, erosion, snow avalanches and rock fall. The measures include afforestation to reduce snow avalanche release, modification of river banks and beds to reduce torrent hazard, revegetation to reduce erosive rock fall from till deposits, and the use of local wood to prevent release of rock fall as well as forest management to reduce block velocity and runout.

The Norwegian NBS proposal, organized by Oppland County Administration, is to reduce flooding, erosion, and problematic redeposition in a confluence zone between a tributary and the main river. The measure is a green, receded barrier, to provide flooding space for the river and secure adequate conditions for the riparian vegetation and several red-list species.

PHUSICOS aims to involve stakeholders in Living Lab processes at the demonstration sites and has succeeded to different degrees depending on the starting point of the NBSs towards their implementation. Baseline surveys of key monitoring parameters are also being performed for selected measures at the three sites.

The main challenges include getting the most representative stakeholders involved in the Living Lab process, and, perhaps most important, adhering to the local laws and regulations, including environmental and tendering processes. These local regulations are already delaying the progress towards implementation of the measures within the time frame of PHUSICOS. The presentation will elaborate on the selected NBS, their co-benefits and on the challenges, which may be limiting factors for such projects.

How to cite: Solheim, A., Oen, A., Kalsnes, B., and Capobianco, V.: H2020 'PHUSICOS': Nature-based solutions to reduce hydro-meteorological risk in rural mountain areas, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9540, https://doi.org/10.5194/egusphere-egu2020-9540, 2020.

The European Horizon RECONECT Project (Regenerating ECOsystems with Nature-based solutions for hydro-meteorological risk rEduCTion) aims to contribute to a European reference framework on NBS by demonstrating, upscaling and spreading large-scale NBS in rural and natural areas.

The Italian RECONECT demonstrator is set in the Portofino Natural Park, which represents a unique natural landscape element with high ecologic, social, and economic (touristic) value and severely endangered by hydro-meteorological hazards.

The Portofino Promontory is historically affected by geo-hydrological events. They can produce natural instability processes related to the interaction between meteorological phenomena and the geological environment, which can potentially cause loss of the exposed elements at risk, as happened in the past. The more frequent processes are: shallow landslides and flash floods, sea-storm surges, rockfalls and mud-debris flows. Often, different processes can occur simultaneously during an intense meteorological event, interacting each other and causing an avalanche effect.

This research introduces the NBS interventions proposed in the RECONECT case study of Portofino over two pilot catchments (San Fruttuoso and Paraggi basins), visited by thousands of tourists all over the year. The project envisages the setting up of meteorological-hydrological stations for studying and monitoring geomorphological processes.

In particular, RECONECT project foresees the selection, installation and operation of hydro-meteorological instruments that include three weather stations, two hydrometers and two cameras to monitor small and very steep catchments.

Monitoring activity include the use of remote sensing survey LIDAR data, orthophotography and infrared aerial photography, whose acquisition has been carried out in January 2020.

Remote sensing and monitoring data are used to quantitatively assess the morphological features and processes, allowing to: a) evaluate the critical-instability areas along the slope and channels and to support the reconstruction of dry stone walls of the widespread terraced areas; b) evaluate the potentially more susceptible source areas of mud-debris flows and the identification of thresholds in meteorological conditions.

In relation to future projections of natural, social and economic impacts of climate change, NBS represent a relevant mitigation and adaptation strategy for the Portofino case study, which may be upscaled at national and international level.

How to cite: Faccini, F., Luino, F., Marchese, A., Paliaga, G., and Turconi, L.: Hydro-meteorological monitoring activities in Portofino Natural Park (Italy) as demonstrator of the H2020 RECONECT project: preliminary results, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-16946, https://doi.org/10.5194/egusphere-egu2020-16946, 2020.

Nature-based solutions (NBS) for soil protection generally involve planting trees to provide effective soil reinforcement, stability and resilience over time. Atmospheric carbon accumulates in both plant and soil materials as the tree cover develops and establishes on a given NBS. However, the carbon stored in a given NBS is subjected to continue cycling as a result of decomposition and soil respiration processes, both linked to the soil’s water content. Consequently, carbon cycling rates within NBS could be regulated by the partition of rainfall into throughfall, dripfall and stemflow at the tree’s canopy. Yet, quantification of soil carbon fluxes related to eco-hydrological processes occurring at the plant-soil-atmosphere interface is rare and needs further investigation. As a result, a figure on the carbon footprint of NBS remains inaccurate. The aim of this study was to quantify soil carbon fluxes under changing meteorological conditions in a tree-vegetated embankment to ascertain the effect of rainfall partition at the tree’s canopy on carbon cycling. To this end, we investigated rainfall partitioning and soil carbon fluxes under six adult tree individuals of Populus nigra L., Dyospiros kaki Thunb., and Melia azedarach L. growing on an embankment in Xuzhou, China. The results showed that soil carbon fluxes were substantially higher on rainy days than on dry days. Nonetheless, we did not find convincing evidence suggesting that rainfall partition at the trees’ canopy contributed to the regulation of the soil carbon cycle. Herein, we discuss experimental limitations that should be addressed in future work to verify the eco-hydrological effect of vegetation on soil carbon fluxes in established NBS, as well as approaches for quantifying the carbon footprint of NBS.          

How to cite: Gonzalez Ollauri, A. and Ma, J.: Eco-hydrological soil carbon fluxes in established Nature-based solutions for soil protection, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1463, https://doi.org/10.5194/egusphere-egu2020-1463, 2020.

The concept of ecosystem services (ES) can help to build a bridge between hydrology, nature, and society. In recent decades, Europe experienced severe catastrophic flood events. Simultaneously, the Floods Directive calls for the inclusion of ES as additional decisional support in flood management. In order to implement flood risk prevention while maximizing the benefits of nature to the society, a better understanding of the floodplains’ ES is required.

The study on the added value of floodplains in Europe has the aim to provide scientific support and answers to the following questions:

• What are the most frequent ES in European flooding areas’ ecosystems? What are the differences and trends of investigated ES among the European countries?
• Which environmental and societal factors are significant to explain the monetary value of floodplains’ ES in areas where no studies haven’t been conducted yet?
• Can ES be used in real case studies to support decision-making in the field of flood risk management?

To answer these questions, a database containing ES studies and their assessed results in the last 20 years was set up and enriched with freely available geo-physical (e.g. land cover) and socio-economic (e.g. population) data. A meta-regression analysis is then applied to the ES values with the aim of extracting a value-transfer function for areas that haven’t been investigated yet. This allows estimating the ES monetary values of proposed floodplain restoration measures in different pilot areas of the Danube River Basin. The work done will help to prove the profitability of nature-based solutions to decision-makers and stakeholders affected by flood risk.

How to cite: Perosa, F., Fanger, S., Zingraff-Hamed, A., and Disse, M.: A meta-analysis of ecosystem services values of European floodplains: database setup and case study application, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4718, https://doi.org/10.5194/egusphere-egu2020-4718, 2020.

Slow-moving deep-seated gravitational slope deformations (DSGSDs) cause constant deformation of the earth’s surface accompanied by damages on superimposed infrastructure. In order to sustain livelihoods in DSGSD affected regions, mitigation measures aiming to reduce the deformation rate are required. Nature-based solutions (NBS) provide an effective and sustainable alternative or addition to conventional technical engineered interventions. A comprehensive monitoring of the landslide movement and its hydrological drivers are essential for identifying and designing effective NBS. This contribution presents a concept of potential NBS to mitigate the impact of the Vögelsberg landslide (Tyrol, Austria). The developed NBS framework relies on geodetic and hydrological monitoring results that play a central role in identifying and quantifying landslide drivers and assessing the potential of modifying them. Furthermore, monitoring data can reveal the success of NBSs after their implementation. The landslide movement is monitored by terrestrial laser scanning (TLS), unmanned aerial vehicle laser scanning (ULS) and by means of an automatic tracking total station (ATTS). The slope’s hydrological conditions are monitored by piezometers in groundwater wells and monthly measurement campaigns of hydrological parameters such as discharge, electrical conductivity, temperature and stable water isotope ratios at springs, groundwater wells, drainages, streams as well as in precipitation and snow. Landslide displacement rates in the order of 5.2 cm/a for the more fluctuating part and 1.7 cm/a at the constantly creeping part of the landslide were determined. Variations in movement rates throughout the observation period correlate with groundwater level fluctuations which by themselves are triggered by preceding long-lasting precipitation or snowmelt events. Time series correlations indicate a time delay of water input and landslide acceleration of less than one month. Detailed hillslope investigations have shown that infiltration of stream water into the subsurface is one important process contributing to groundwater recharge. Sealing porous parts of streams with natural and impermeable materials is therefore suggested as one appropriate NBS. Stable water isotope analysis of groundwater and precipitation indicate that winter precipitation contributes more to groundwater recharge than summer precipitation. This finding demands further investigations on how snowmelt infiltration can be avoided using NBS. Strengthening the evapotranspiration with an adapted forest management on recharge areas would represent another natural mitigation measure contributing to a deceleration of the landslide. The effect of elaborated NBS on the groundwater recharge and slope stability will be analysed in detail by using numerical models.

How to cite: Pfeiffer, J., Zieher, T., Schmieder, J., Rutzinger, M., Polderman, A., Engl, D., Anegg, J., and Lechner, V.: Monitoring-based identification of nature-based solutions to mitigate the impact of deep-seated gravitational slope deformations, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18263, https://doi.org/10.5194/egusphere-egu2020-18263, 2020.

Several recent large flood events have had severe economic and social impacts. The winter 2015-16 UK floods resulted in 16,000 properties flooding and damage to critical infrastructure. It is increasingly being recognised that traditional approaches of flood defence are not sustainable due to the pressures of climate change and economic constraints. The solution to the flood risk problem in cities is no longer seen as being just on-site, and thinking is shifting upstream and to the catchment/landscape scales, known as Nature-Based Solutions or Natural Flood Management (NFM). The approach consists of measures that “Work with Natural Processes”, such as storing water in ponds, and slowing the flow in rivers. The evidence for the impacts is strong at the local scale, but the larger spatial scale impact is highly uncertain due to the cumulative impacts resulting from amplifying/mitigating effects of different interventions, controlled by spatial location and storm-track interaction.

To date, Nature-Based Solution schemes have proceeded on an opportunistic basis, without a clear design strategy (which measure and where to implement it). However, if schemes are implemented without clear understanding of their impacts, they may, at best, fail to achieve the optimum flood reduction benefit downstream, or, at worst, make flooding more severe (if implemented in inappropriate locations, when tributaries’ flows are synchronised).  

Impacts of NFM measures are spatially and temporally dependent i.e. the same intervention in two locations will have different effects on flows, and the same intervention will have different impacts during different storm events. Therefore, it is essential that when strategically designing NFM schemes for catchments, that WHERE? and WHAT? are answered together to optimise the impact, as it is possible that whilst upstream NFM may be beneficial locally it may make tributary peaks coincide and make flood magnitudes worse downstream. Here we demonstrate the importance of the spatial configuration of Nature-Based Solutions on their catchment scale effectiveness in reducing flood risk.

How to cite: Pattison, I.: Nature-Based Solutions: Dependency of Effectiveness on Spatial Configuration, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10899, https://doi.org/10.5194/egusphere-egu2020-10899, 2020.

Nature-Based Solutions (NBS) could be effective measures to respond to land degradation processes and events such as floods. This study demonstrates how to evaluate the benefits of afforestation being a long-term NBS utilizing a combination of an innovative monitoring technology and modelling approaches. The catchment Geroldsbach-Götzens is used as a lead catchment, being typical for numerous Alpine catchments with interacting urban and torrential features. The catchment comprises NBS such as afforestation being installed in the torrent since the early 1950ies.

We use an artificial rainfall runoff test site to test different scenarios and analyse runoff behaviour. Besides artificial rainfall simulations, the site is equipped for continuous monitoring of natural occurring rainfall runoff events. In that course, precipitation, snowfall, snow cover, air and soil parameters are assessed. The development and effects of measures over time are modelled utilizing as well the monitoring data. For generalizing and upscaling of the findings, especially with regard to (a) land use in torrents and (b) land use at the urban scale, models are realized as well for other catchments. Beyond realizing historic and current situations exclusively, land use scenarios for assessing the change over time and potential future scenarios are to be modelled.

Results can provide a quantification of the benefits and co-benefits of NBS such as: reduction of flood risks, improvement of the recreational qualities, and enhancement of biodiversity. Experience from the field can show the best practices and how to develop innovative ways that can be used for upscaling. Land use and climate scenarios give an indication of changes that can be expected over time and potential future scenarios. Overall findings lead to a better understanding of long-term implementation of NBS and support decision making of stakeholders in other catchments.

How to cite: Molenaar, R., Kohl, B., Stepanek, L., Kleidorfer, M., and Achleitner, S.: Regenerating ecosystems with Nature-Based Solutions: demonstrator study Inn River Basin, Austria, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7106, https://doi.org/10.5194/egusphere-egu2020-7106, 2020.

Nature-based solutions are an important component of integrated flood mitigation strategies for improving both the protection against hazardous flood events and the ecological conditions of river-floodplain systems. In order to be able to take these types of measures into account in upcoming flood management decisions, it must be possible to reliably estimate their effects on flood events. Therefore, this study focuses on a more general view on the catchment dependent contribution of combined river and floodplain restoration measures to the strengthening of river retention and flood protection. Furthermore, the importance of considering site-specific circumstances (e.g., the superposition of the flood waves of the main river and its tributaries), is evaluated.

The study is based on five investigation areas in Bavaria (Germany) with various topographic properties and different spatial scales (~ 90 – 560 km²). For each catchment, a physically based hydrological model (WaSiM) was coupled with the two-dimensional hydrodynamic model HYDRO_AS-2D by means of direct and diffuse inflow boundary conditions. Five flood events with various rainfall characteristics (advective/convective) and different return periods (5, 20 and 100 years) were generated with WaSiM. The holistic restoration scenarios are implemented by catchment dependent modifications of river channels and floodplains. As the aim of this study is to analyze the maximum possible efficiency of the restoration scenarios, it is assumed that almost the entire floodplain is available for the implementation of these measures. Highly restricted areas (e.g., settlement & industrial areas, important infrastructure) are excluded from this assumption. First results show that the peak discharge attenuations resulting from the restoration measures are exemplarily dependent on the characteristics of the floodplains (e.g., slope and extent) and the volumes of the flood events. It could be shown that the largest peak discharge attenuations (up to 28 %) and retardation (up to 8 h) occur in catchments with relatively flat and wide floodplains in combination with comparatively small flood volumes. Furthermore, the effectiveness of these measures can be considerably affected by local superposition effects with incoming tributaries. These effects can have site and event specific positive or negative impacts on the peak discharges and may not be neglected when planning restoration measures.

Based on these investigations, it is possible to evaluate if catchments are likely to be suitable for river and floodplain restoration in the course of flood management decisions. However, the effectiveness of the measures is always influenced by a combination of many area-specific factors that can only be predicted to a limited extent and therefore requires the modelling of an area.

How to cite: Neumayer, M., Teschemacher, S., Merk, F., and Disse, M.: Retention potential analysis of river restoration and floodplain measures in different catchments of Bavaria, Germany, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13199, https://doi.org/10.5194/egusphere-egu2020-13199, 2020.

Planting of herbaceous vegetation on riverbanks is a measure for reducing river flooding occurrence, through the protection of the bank face from fluvial erosion. In fact, mitigating the erosive action of the water flow and improving soil resistance by increasing the strength of the bank material with their roots, such nature-based solution reduces the risk of local and shallow instability mechanisms that may lead to the collapse of levees and riverbanks during flood events.

While there is nowadays a wide experience on the use of vegetation over hill slopes and other ‘mainly dry’ soil conditions, a carefully calibrated design approach to understand the vegetation impact inside the river bed and banks, under flood flow forcing, represents a much less explored research field, which is investigated in the Open Air Lab-Italy in the EU H2020 project OPERANDUM. To address this important and complex problem, a combined use of laboratory experiments, site monitoring and numerical analysis is required to improve actual procedures and standards.

In the present work, the principal focus is on the design, preparation and deployment of the laboratory activities, extremely rare in the literature, with a discussion on the first experimental findings and observations. A set of experiments in a recirculating, tilting hydraulic flume are designed and implemented, in order to gain, in a controlled environment, information on the influence of the vegetation on both hydraulic and erosive processes.

During the experimental tests, water flow depth and velocity are monitored through UPV Ultrasound Velocity Profilers and Particle Tracking Velocimetry, in order to estimate the tangential stress at the soil-water interface. The main challenge resulted to be the estimation of the volumes of soil eroded during the experiments, due to the very limited quantities that are eroded and to the particularly fine-grained texture of the soil (that was collected from a real embankment of the river Panaro, reference case for the Open Air Lab).

The laboratory experiments allowed to compare the impact of different flow regimes (varying the channel slope, different flow velocity fields were tested) over soils vegetated with both shallow-rooted and deep-rooted perennial herbaceous species, and the results will successively help to analyse the hydraulic and erosive processes on the riverbanks, where such vegetation cover will be installed.

How to cite: Toth, E., Guerrero, M., Gragnano, C. G., Domeneghetti, A., and D'Agostino, D.: Laboratory experiments for analysing the impact of herbaceous vegetation on riverbank erosion, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19572, https://doi.org/10.5194/egusphere-egu2020-19572, 2020.

The economic advantage of NBS solutions aiming at mitigating water-risk is widely put forward as an argument for their development. There is nevertheless limited scientific evidence to support this argument. This paper therefore elaborates a methodological framework for the economic assessment of NBS and presents its application to three NAIAD case studies (the Lez catchment, France; Rotterdam, the Netherlands and Brague catchment, France). Robust methods are particularly applied for the estimation of the benefits associated with NBS. Physical models coupled with damage estimation models are developed to estimate the avoided damages generated by NBS. A diversity of ecosystem service valuation methods are also applied to evaluate the monetary value of NBS co-benefits: contingent valuation (Brague), choice experiment (Lez) and direct valuation methods (Rotterdam). We estimate the cost of implementation and maintenance mainly through the transfer of values coming from studies in similar contexts. Proxies are used to estimate the opportunity costs associated with the development of NBS. Finally, these estimations are compiled in a cost-benefit indicator allowing the estimation of the economic efficiency of NBS strategies. The study confirms that the cost of implementation and maintenance of NBS strategies is lower than the cost of grey solutions for the same level of water risk management, emphasizing the better cost-effectiveness of these solutions. Benefits in terms of avoided damages are however not sufficient to cover investment and maintenance costs. The cost–effectiveness of NBS strategies, which are combinations of individual NBS measures, may be improved by combining cost effective individual NBS measures. There is indeed a very large heterogeneity of cost-effectiveness of individual NBS measures (cost/m³ of water retention). Results also reveal that co-benefits represent the largest share of the value generated by NBS strategies. It is therefore of utmost importance that co-benefits are integrated in the economic valuation of NBS for them to be judged economically efficient. This conclusion must be taken into account in the elaboration of NBS funding strategies.There is finally no clear-cut conclusion on the overall economic efficiency of NBS throughout the case studies. Lez reveal a positive cost-benefit analysis, while Rotterdam and Brague cases do not. Results are therefore case-specific and confirm the importance to carry out thorough economic valuations of a diversity of strategies at each sites, including NBS, grey and hybrid solutions, in order to identify the most adequate strategy for water risk management and to address territorial challenges.

How to cite: Le Coent, P., Herivaux, C., Calatrava, J., Marchal, R., Mouncoulon, D., Benitez-Avila, C., Altamirano, M., Gnonlonfin, A., Graveline, N., Piton, G., and Daartee, K.: Is-it worth investing in NBS aiming at mitigating water risks? Insights from the economic assessment of NAIAD case studies, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22537, https://doi.org/10.5194/egusphere-egu2020-22537, 2020.

The evidence to date shows that hydro-meteorological risks are likely to become more extreme in the foreseeable future. The continuously changing climate has also led to increasing pressure on the environment and human society. For these reasons, effective and sustainable methods for hydro-meteorological risk management are becoming more important. As an umbrella concept, Nature-Based Solutions (NBS) have been promoted due to their potential in reducing hydro-meteorological risk, adapting to climate change, and providing a wide range of co-benefits to nature and human well-being. The procedure of efficient planning and selection of NBS is a complex process that requires the involvement of multiple stakeholders. Measures need to be evaluated taking into account their primary function for hydro-meteorological risk reduction, potential co-benefits and specific local requirements. This paper presents a methodology to select NBS measures for reducing hydro-meteorological risk and increase co-benefits at the river basin scale. This is achieved by using stakeholder opinion to identify the importance of benefits and NBS in the area under consideration. A broad range of benefits has been included, such as risk reduction, water quality, habitat structure, biodiversity, socio-economic, and human well-being. This methodology has been applied to the case study of Tamnava River Basin in Serbia from RECONECT project. The results from this case study highlight the importance of involving local stakeholders in early stages of selection and implementation of NBS as part of the wider stakeholder co-creation process. The results also indicate the potential of the new methodology to assist decision-makers in the selection and implementation of NBS.

How to cite: Ruangpan, L., Plavšić, J., Voijnovic, Z., Bahlmann, T., Alves, A., Randelović, A., Todorović, A., and J. Franca, M.: Involvement of stakeholders in the selection and implementation of Nature-Based Solutions for hydro-meteorological risk reduction, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20068, https://doi.org/10.5194/egusphere-egu2020-20068, 2020.

Forest harvesting increases nutrient and sediment load to the adjacent watercourses and further deteriorates water quality. Effect is stronger after heavy rainfall events, which are predicted to be more frequent in future and thus, posing an increased risk of leaching of dissolved elements and suspended solids. There are several potential nature-base solutions (NBS) available to mitigate export of nutrients and suspended solids. The efficiency of most of them is based on their ability to reduce flow velocity and ability to capture eroded suspended solids and nutrients before they enter to the receiving water body. Such NBS include e.g. sedimentation ponds and pits, as well as peak flow control structures, constructed wetlands and overland flow areas. Furthermore, certain forest management practices such as continuous cover forestry are assumed to decrease leaching of nutrients and suspended solids.

Nutrient and sediment loading emerges as a result of complex processes that have spatial and temporal variability. In order to be able to assess the current and future status of nutrient and sediment loading, the factors influencing those and possible management actions to mitigate negative impacts, we need a systemic approach based on modelling tools. In Finland, the decision support protocol is used for producing catchment scale nutrient and sediment load scenarios including different NBS and their combinations to involve the local land owners and other stakeholders in co-designing the sustainable future for Lake Puruvesi. The decision support protocol (NIM) considers the loading of nutrients and sediment from the terrestrial part of the catchment with each land use separately and combines this with the ecological status of the receiving water body. NutSpaFHy is a grid-based catchment-scale distributed model based on a simplified and computationally efficient hydrological model SpaFHy and is part of NIM enabling the identification of forest management history and its load and anticipation of future, probable forest management and the resulting load. NutSpaFHy includes a nutrient balance component where nutrient uptake, release and storage are quantified grid by grid (16m resolution) at daily scale based on meteorological drivers and spatial data from national forest inventory and soil and topography. After calculating nutrient balance, the export loading component is used, and it includes an exponential delay function which is built upon the hydrological simulation and nutrient balance quantification. NutSpaFHy is simulating export loading with good performance level during climatological events in boreal forested catchments. NutSpaFHy utilizes open source datasets available, including forest resource data, digital elevation model (DEM) and soil maps. Built upon simulated forest growth information, soil water table and saturation deficits modelled by SpaFHy, a grid-scale computation of daily N and P balance was conducted.

Nutrient loads are calculated in current and future climate with two different logging scenarios to assess the functioning of the NBS in mitigating nutrient loading. The results will show the role and potential of NBS in future climate.

How to cite: Salmivaara, A., Ukonmaanaho, L., Leinonen, A., Finér, L., Korhonen, N., Tuomenvirta, H., and Laurén, A.: Using NutSpaFHy model to assess nature-based solutions for mitigating nutrient and sediment loading under changing forest management and climate scenarios, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21457, https://doi.org/10.5194/egusphere-egu2020-21457, 2020.

As part of H2020 OPERANDUM project, a multi-dimensional, open and user-friendly platform is being developed, named OPERANDUM Geospatial Information Knowledge Platform (GeoIKP), which enables stakeholders and end-users to improve their knowledge of nature-based solutions (NBS) as a long-term and sustainable measure for mitigation and reduction of flooding, coastal erosion, landslide and other hydro-meteorological hazards.

 This contribution offers an overview of GeoIKP and discusses in detail some of the innovative aspects of the platform, such as a the integration of a NBS data management portal with a web application offering advanced webGIS tools, a comprehensive catalogue of NBS, as well as analytical algorithms to demonstrate the effectiveness of NBS in reducing hydro-meteorological risks.

The platform design is being based on intuitive techniques, ease of access, dynamic navigability, interactive knowledge management, and multiple format compatibility. It empowers the multiple and diverse actors involved in the NBS co-design/co-development process (policymakers, citizens, enterprises, scientists, etc.) to visualize and query geo-referenced data for the specific area of interest.

In its first - yet preliminary - release, GeoIKP already offers a variety of functionalities and geo-referenced data of relevance for NBS, while at the same time it provides more standardized ways for NBS data (and metadata) management and cataloging.

 We conclude by reflecting on some of the current challenges associated with NBS data, such as adequacy and discoverability.

How to cite: Leo, L. S., Vranic, S., Kalas, M., Debele, S. E., Bertini, F., Ommer, J., Montesi, D., Pavlova, I., Kumar, P., and Di Sabatino, S.: A Geospatial Information Knowledge Platform for NBS tackling hydro-meteorological hazards: key features and innovative aspects, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18851, https://doi.org/10.5194/egusphere-egu2020-18851, 2020.

PHUSICOS platform aims at gathering nature-based solutions (NBS) relevant to reduce hydro-geological risks in mountain landscapes. The platform can be accessed directly through a web portal It is based on an Open Source CMS website, including a filer to store documents and a map server to bring ergonomic and powerful access. Furthermore, a list of metadata has been proposed to structure the information. These metadata have provided the baseline for database content and the platform has been filed with the literature review of existing NBSs related to extreme hydro-meteorological events. In particular this review integrates existing case studies presented in existing platforms. That is why PHUSICOS platform has been built to be coherent with these platforms. Nine platforms were identified during the inventory of NBSs of interest for PHUSICOS: Oppla, Think Nature, NAIAD, The European Climate Adaptation Platform (CLIM-ADAPT), Urban Nature Atlas, Prevention Web, Adaptation Community, PANORAMA – Solutions for a Healthy Planet and RECONNECT.

Contribution to PHUSICOS platform is open to registered users. A questionnaire based on relevant data, necessary for the definition and identification of the NBS (metadata, to be used for searching the NBSs within the platform) has been defined to enter new entries. Next step will be the implementation of the evaluation for providing a ranking list of NBS according to a multi-criteria approach.

The platform now gathers 46 entries and will be enriched all along the project, in particular with NBS that will be implemented in PHUSICOS demonstrator sites: the Serchio River Basin (Italy), the Valley of Gudbrandsdalen (Norway) and the Pyrenees (Spain-France-Andorra).

The full structure of the platform and preliminary content are presented in this work.

How to cite: Baills, A., Bernardie, S., Frezot, O., and Marquis, G. and the PHUSICOS Team: PHUSICOS platform: Nature-based solutions to reduce risk in mountain landscapes, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2710, https://doi.org/10.5194/egusphere-egu2020-2710, 2020.

Urban street trees provide multiple ecosystem services to city residents. In the Taipei city of Taiwan, street tree pruning is periodically applied due to disastrous prevention of typhoons or storms. To understand how pruning intensity affects the value of ecosystem services, we evaluated the changes of ecosystem services provided by a total of 87,014 street trees in Taipei in terms of pollution removal, carbon storage, gross carbon sequestration, and runoff avoidance. The current status of each ecosystem service was calculated using i-Tree Eco developed by US Forest Service based on the street tree inventory conducted by Parks and Street Lights Office, Taipei City Government during 2015 to 2017. Inventory information included tree species, diameter at breast height (DBH), tree height, and their locations. To simulate pruning intensity from 10% to 100%, we adjusted the crown missing rate from the current canopy cover estimated by DBH and tree height and quantified their associated effects on the ecosystem services. Then, for comparison purposes, each ecosystem service was transformed into monetary values using US market value of water, carbon, air pollution removal, and electricity. Our analysis showed that the Taipei street trees currently hold a relatively stable age structure with lower risk of disease or pest outbreak. These trees were estimated to deliver ecosystem services of equivalent value of 5.6 million USD, to which 4.97 million USD was contributed by carbon storage. Based on the pruning intensity simulation, we suggest a 20% or lower pruning intensity considering street trees’ impairment and physiology, to maximize the ecosystem service values. We also recommend landscape managers to monitor and assess the growth and health of the street trees to promote sustainable development in the Taipei city.

How to cite: Cheng, S.-T. and Wei, S.: Pruning intensity of street trees and associated effects on ecosystem services, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3206, https://doi.org/10.5194/egusphere-egu2020-3206, 2020.

Land use and management changes and landscape modifications, including urbanisation and agricultural intensification, have resulted in significant increases in flood risk across the UK in recent decades. To combat this, a shift towards catchment-based flood risk management has seen a marked rise in Natural Flood Management (NFM) schemes applied across the UK. These schemes largely represent mitigation strategies that work with natural processes to restore and augment hydrological and morphological catchment features for enhancing downstream flood resilience through the slowing, storing and filtering of runoff and flow. This has been implemented through the introduction of woody debris, afforestation of floodplains and runoff attenuation features. However, despite growing evidence highlighting their potential benefits, the function of these structures in the landscape and their effectiveness for flood risk reduction is still highly uncertain.

To address this knowledge gap, this study evaluates the effectiveness of a range of larger-scale floodplain and in-channel NFM features for flow attenuation and flood risk reduction.  To achieve this, a two-year field campaign was conducted in Somerset, South West England, involving the collection of continuous discharge, storage volume and local rainfall data at four sites in the Tone and Parrett catchments. The sites contained NFM structures including offline and online storage ponds and in-channel woody debris. Using these data, filling, storing and spilling capabilities were characterised through the utilisation of field-scale DEMs from Structure from Motion (SfM) and manual surveys. Storm events were separated, and key hydrograph characteristics analysed, to determine the effect of NFM structures on high flow events and the potential for flow attenuation.

The results indicate an increase in storage and flow attenuation as a result of the inclusion of NFM. Increases in flow lag time downstream of in-channel features were identified, relative to an upstream gauge. Longer recession limbs were also recorded downstream of storage ponds, illustrating the buffering influence of upstream structures and the consequential slowed water release downstream. Floodplain-based storage structures were found to only function optimally during the largest events, where pond filling could occur directly from the channel and flow is temporarily stored on the floodplain. These results will provide vital evidence for both local and national NFM applications.

How to cite: Lockwood, T., Freer, J., Michaelides, K., Coxon, G., Richardson, T., Brazier, R., Thorne, B., and Webb, L.: Monitoring the efficacy of Natural Flood Management structures on flow attenuation and flood risk reduction, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9619, https://doi.org/10.5194/egusphere-egu2020-9619, 2020.

Hydro-meteorological disasters have shown the fastest rate among all natural disasters. This is due to several factors: i) climate change, ii) population growth and land use change, and iii) poor water management practices. Traditional engineering solutions have shown to be ineffective in responding to such challenges and hydro-meteorological risks in general. In this respect, Nature-Based Solutions (NBS) offer the means to respond to such increasing challenges by providing a range of benefits (i.e., hydro-meteorological risk reduction) and co-benefits (i.e., ecosystems restoration and increase socio-economic values). The need to incorporate numerous benefits and co-benefits into the design of NBS calls for a combination of knowledges and practices from water engineering and landscape architecture. These would be necessary to design an NBS site that have multiple functions that can incorporate multiple benefits and co-benefits. At the same time, NBS should be designed in such way to withstand possible changes and pressures. This in turn calls for novel design practices of NBS to support planning and implementation that can achieve multifunctional and robust results. In this work, a framework for multifunctional and robust design of NBS is addressed. This framework will combine the use of hydrodynamic models, GIS tools, topology analysis, adaptive options analysis, adaptive pathway design, multi-criteria analysis, cost-benefit analysis, and robustness evaluation. The framework will be applied to one of the RECONECT cases and the first results will be presented.

How to cite: Zhong, L., Zoran Vojinovic, Z. V., and Francac, M.: Combining water engineering and landscape architecture practices for multifunctional and robust design of Nature-Based Solutions , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22559, https://doi.org/10.5194/egusphere-egu2020-22559, 2020.

Mitigation of the perceived risks of climate change is urgent issue in many fields. This research focuses on providing information to support decision making in mitigation of hydro-meteorological risks that climate change causes to the water quality in Lake Puruvesi and in its sub-catchment area. This study reviews continuous cover forestry (CCF) and buffer zones as possible nature-based solutions (NBS) that could achieve the goal of keeping the water quality level in study site on current level or improve it. The main research question of this research is: Is it economically cost-efficient to implement continuous cover forestry and buffer zones as nature-based solutions to mitigate nutrient loading in research area so that the water quality will stay at least at the current level in the future?

Previous research has shown that CCF can be economically feasible way to manage forests. In addition to this, continuous cover forestry and buffer zones can reduce nutrient loading from forests to nearby waters. These solutions are evaluated in the framework of cost-benefit analysis which is the main method in this study. The aim is to monetize costs and benefits that NBS implementation will cause. If the net social benefits after analysis are positive, the project should be recommended. In this study recreation values from the study site were obtained by utilizing pre-existing valuation studies made by Finnish Natural Resource Center. Costs on the other hand were derived by using size-structured forest optimization model. The economic loss for forest owners is the difference between their optimal forest management choice, and the optimized solution, where clearcutting is restricted. In the buffer zone case optimization was similar but the costs from buffer zones are directly the maximized profits from forest as the buffer zone is completely left out from any forestry.

In both cases CCF was the optimal forest management regime for the sample forests. When these costs were compared to the benefits this study produced positive net social benefits and hence CCF and buffer zones should be recommended as NBS in the study site. However, there are quite large assumptions made in this study, and further modeling of nutrient flow in study site is required as the quantified impacts of nutrient run-off are still unclear. For this reason, further research is required for more precise analysis regarding quantified impacts.

How to cite: Juvonen, J.: Cost-Benefit Analysis of continuous cover forestry and buffer zones as Nature Based Solutions to preserve water quality level in Lake Puruvesi and in its sub-catchment area., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8171, https://doi.org/10.5194/egusphere-egu2020-8171, 2020.

Nature-based retention measures are an essential part of a sustainable and integrated flood protection strategy and can contribute to a holistic flood mitigation approach. Thereby river restoration measures such as channel widening, or flow path extension to increase the channel meandering represent successfully used components. Coupled with flood plain measures, retarding and retention effects of flood events are possible. These effects are commonly computed applying two-dimensional hydrodynamic modelling approaches. However, these developments rely on high spatial and temporal resolutions which are generally characterized by a high computational demand and are hence time and cost expensive. Thus, the evaluation and derivation of flood routing parameters to reproduce the resulting hydrodynamical processes in hydrological models can provide an effective and fast computation of river restoration scenarios.

The objective in the present study is the derivation and application of flood routing parameters which can account for the effects of river restoration and flood plain measures in hydrological models. Further, this study aims to determine if the catchment and scale specific outcomes and parameter sets are also applicable to a broader range of catchments.

For this purpose, commonly applied flood routing approaches and the associated parameters used in hydrological models (e.g. the kinematic wave approach in the WaSiM model) are investigated for catchments of different scales in Bavaria (Germany) and for flood events of varying characteristics (e.g. return period, flood volume). To determine the effects of channel restoration and flood plain measures, two-dimensional hydrodynamic models (HYDRO_AS-2D) are set up to simulate the current state as well as restoration scenarios. Based on the simulation results of the hydrodynamic models, the parameters of the flood routing approaches are calibrated to match the catchment specific restoration effects for a first set of river sections. Catchment and scale dependent parameter sets (dominating valley type, flood plain slopes) are then derived to reproduce the specific river restoration. First results of the calibration of the parameter sets show a satisfying fit of the hydrological model to different restoration scenarios of the hydrodynamic model. For the validation of the derived parameter sets of the flood routing methods in the hydrological model additional river sections of the hydrodynamic models are subsequently investigated.

The implementation of the new flood routing parametrization of the hydrological models is finally examined as an alternative resource efficient way of calculating the effects of river restoration scenarios. Moreover, the applicability of the outcomes as a cost-efficient alternative compared to hydrodynamic models in land use planning and risk assessment is assessed and discussed within the frame of river restorations as flood mitigation measures.

How to cite: Merk, F., Neumayer, M., Teschemacher, S., and Disse, M.: Evaluation of adapted hydrological flood routing approaches as a cost-efficient contribution for the assessment of nature-based flood mitigation measures , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13150, https://doi.org/10.5194/egusphere-egu2020-13150, 2020.

In recent years, the risk of flooding disasters caused by climate change has increased, and a new concept of runoff sharing has been proposed in China. It is an operation method based on the area of ​​the catchment from the perspective of water conservancy. However, the basin area is also a spatial unit of human economic activity. Social and economic development and the distribution of runoff responsibilities clearly show a mutual measurement relationship, and the land has a certain social responsibility to handle its own runoff. How can it be distributed fairly and efficiently? The issue of responsibility for runoff sharing has become an important issue for joint initiatives in the field of soil and water. 

In the case of considering the watershed as a spatial scope, in addition to considering its own hydrological properties, there are also socioeconomic development issues that should be clarified and discussed step by step. Therefore, this study attempts to use the three-stage data envelopment analysis (DEA) method to consider hydrology The concept of interaction with the socio-economic environment takes into account the impact of exogenous factors on the allocation of runoff responsibility, and evaluates the efficiency of runoff responsibility. In view of this, from the standpoint of the government and residents sharing the runoff, this study effectively combines the different types of data of the social, economic, and ecological environments in the catchment areas to carry out a comprehensive assessment, and weighs out the optimal distribution efficiency of the overall river basin. 

This study is divided into three parts to clarify the distribution of runoff responsibilities, which are divided into: (1) Establishing an assessment framework for the distribution of river basin runoff responsibilities: Based on the analysis of the spatial unit of the catchment area, an attempt is made to integrate different regional development conditions, which can be summarized Appropriate and appropriate distribution methods; (2) Weighing the fairness and efficiency of the distribution of runoff responsibilities in the spatial unit of the watershed: Point out the current runoff responsibility distribution model and characteristics of the catchment area; (3) Attempt to develop the principles for the use of land use planning, Apply the concept of runoff responsibility to land use planning. 

Based on the results of this study, a more fair way to distribute runoff responsibilities is proposed, and a new perspective on social natural equality from the river basin scale is clarified. The key factors that affect the distribution of runoff responsibilities are clear. Efficiently undertake total runoff and provide policy planning advice. Try to discuss the issue of runoff responsibility allocation from the field of urban planning, provide river basin runoff responsibility with a planning vision, strengthen the spatial thinking of water and soil dialogue, and look forward to providing a new model of river basin governance in extreme climates. 

How to cite: Kuan Ling, C., Hsueh Sheng, C., and Hao Teng, C.: Evaluation of Environmental Efficiency of Runoff Responsibility Distribution from the Perspective of Equity and Efficiency, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-16932, https://doi.org/10.5194/egusphere-egu2020-16932, 2020.

In the recent past, severe flooding have caused major natural disasters leading to severe damage to public property, infrastructure and human life. The threat of flooding can be attributed to rapid growth in population, uncontrolled urban expansion, global warming and climate change. It has been reported that more than 100,000 people were killed and over 1.4 billion people were affected worldwide due to flooding over the past ten years. The main contributing factors of flooding that affect death or injury to people include flood depth, velocity of flood flow and the degree to which people are exposed to flood in the region. A significant increase in rate of flooding occurred due to decrease in vegetation cover and increase in the imperviousness at urban areas, leading to decrease in the efficiency of urban drainage system that increase proneness of flooding. This study identifies an innovative approach to flood control by deployment of a Nature based solution (NBS). NBS is relatively new approach to tackle flooding and is a solution framed with an inspiration and support from nature. This research focuses on addressing the following three questions: which NBS to deploy, how to identify the ideal site for deployment of the selected NBS, and how to quantify the effectiveness of the deployed NBS in terms of flood control/reduction? As a part of the EU Horizon 2020’s OPERANDUM project, the case study is being conducted at Dublin as the Open Air Laboratory Ireland. The NBS implementation study has been initiated along with the partnership of Dublin City Council. Preliminarily, city planning rules and land development guidelines were reviewed from Dublin and green roof was selected as the potential NBS. Subsequently, rainfall-runoff based hydrological modelling was performed to assess the potential flood hazard areas and to identify an effective location for implementation of NBS. For this purpose, the hydrological model was simulated with and without the presence of NBS at different potential locations and the site exhibiting highest flood control was selected to be the optimal location. The selected location is close to the Dublin Port and adjacent to River Liffey, which is the main river in Dublin. In order to show the effectiveness of the green roof NBS, real world data has been collected before and after implementation of the NBS to assess its effectiveness in real world framework.

How to cite: Sarkar Basu, A., Basu, B., Sannigrahi, S., and Pilla, F.: Deployment of Green roof top as a Nature Based Solution in Dublin, Ireland, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12215, https://doi.org/10.5194/egusphere-egu2020-12215, 2020.

Nature-based solutions (NBS) are the bundle of natural and ecological functions that are proven to be beneficial to address varied socio-ecological challenges at cities. The conceptual adaptation of NBS alternatives in managing leading issues such as climate change and its impact on community well-being, sustainable uses of natural resources, encouragement for using soft engineering approaches for nourishing synergic benefits of natural capitals, empowering population health and reducing disaster risk are increasing substantially over the past few decades. The other term Ecosystem Services (ESs) refers to the variety of supports and benefits that humans obtained from the natural environment, which add human well-fare and improve the overall socio-ecological status at cities. NBS alternatives include increase in green areas by urban forestry and plantation, preserving urban inland water bodies and wetlands, introducing sustainable, cost-efficient, and environment-friendly urban drainage and sewage systems, reducing the impervious surface cover by increasing green cover, etc. However, substantial evidence is required to understand the importance of NBS alternatives and its implication in producing various regulatory, provisioning, supporting, and cultural urban ecosystem services that collectively produce ranges of economic, social, and environmental supports and benefits. This study performs a thorough quantitative and qualitative assessment to explore the possibilities of adopting varied NBS alternatives to reduce environmental problems in a city and to quantify the economic values of different NBS alternatives using spatially explicit biophysical and economic valuation approaches. Two spatially explicit integrated models Integrated Valuation of Ecosystem Services and Trade-off (InVEST) and Soil Water Assessment Tool (SWAT) was used to quantify the biophysical and economic values of different NBS alternatives and ESs in Dublin, Ireland. The outcome of the study could be a reference to the concerned stakeholders, decision-makers, urban planners, and land administrators for adopting suitable NBS alternatives in managing the uprising environmental and socioecological issues in a city region.

How to cite: Sannigrahi, S., Basu, B., Sarkar Basu, A., and Pilla, F.: Ecosystem service-based approach for evaluating the effectiveness of nature-based solution in mitigating climate change and land degradation issues in a city region, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19413, https://doi.org/10.5194/egusphere-egu2020-19413, 2020.

Due to its rugged morphology and a general lack of flat areas suitable for cultivation, Liguria region is widely characterized by slope terracing, carried out by its inhabitants for centuries. Slope terraces are usually retained by dry-stone walls; secondly, by retaining walls made of stones bounded by lime mortar or by grassy edges, in this case characterized by the absence of retaining structures.

The widespread abandonment of rural areas that occurred in the second half of the last century resulted in a diffuse lack of dry-stone walls maintenance, which is a fundamental activity in order to keep the function of dry-stone structures. Such aspect, together with an increasing occurrence of extreme hydro-meteorological events over the last years, accelerates the dry-stone walls decay and collapse, as well as the instability of single terraces and consequently of the whole terraced slope.

This is the case in which the Cinque Terre National Park (eastern Liguria, north-western Italy) is involved, a narrow strip of land close to the seaside and characterized by small valleys and terraced slopes showing high steepness values. This anthropogenic landscape represents a high-value peculiarity attracting more than three million tourists every year.

The main objective of the project is to demonstrate how an ancient technology, drystone walling, can be effectively used to improve the resilience of the territory to climate change by adopting a socially and technically innovative approach. Stonewalls4life started in the second half of 2019 involving many subjects, both public bodies and privates, in a multidisciplinary workgroup.

More into details, it will be demonstrated on a specific site measuring 6 hectares (Manarola, Cinque Terre) the climate change adaptation effectiveness of the approach by restoring abandoned drystone terraces, making them more resilient with innovative techniques; at the same time, three additional sites were identified in order to test the approach under different circumstances (two within the same territory, one in Catalonia – Parc del Garraf – with dissimilar conditions). Furthermore, from a scientific point of view, the project will allow to carry out a quantitative and objective assessment of the dry-stone walls effectiveness against extreme rainfall events, through the installation of several multiparameter stations that will record in continuous a set of geo-hydrological parameters associated to walls.

An extensive and detailed geological and geomorphological survey activity along with GIS analysis and bibliographical research has been carried out in order to create a geological-structural model of the aforementioned site and to identify its geomorphological features. Moreover, an accurate mapping and analysis of dry-stone walls has been performed employing an innovative approach developed in the frame of the project and based on field-surveyed and remotely-sensed data.

The outcomes represent a solid base for the implementation of the future phases of the project, in particular to understand the relationship among the geological, geomorphological and anthropic features of the area with the terraced-slopes stability in order to develop an accurate management plan concerning the dry-stone walls recovery activity.

How to cite: Vigo, A., Mandarino, A., Pepe, G., Raso, E., Miretti, U., Bernini, A., and Firpo, M.: STONEWALLS4LIFE - using Dry-Stone Walls as a Multi-purpose Climate Change Adaptation tool: preliminary results in terms of geological and geomorphological quantitative analysis., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21358, https://doi.org/10.5194/egusphere-egu2020-21358, 2020.

Global warming induced climate change is bringing periods of extremely hot summer days called heatwaves across the world. Its frequency, intensity and magnitude have escalated multifold in recent decades and have been predicted to keep intensifying. Many past studies have only focused on cities for heatwave risk assessment overlooking the risks in suburban and rural areas. The aim of this work is to form a scientific framework for preparing and managing the human-health impacts of heatwaves in more pastoral regions. We associated  the extreme temperature with mortality to evaluate its risk using recent data on daily-deaths and maximum temperature from nine counties of southeast England for the period of 1981-2014. The reproduced methodology will also be applied to OPERANDUM project’s test regions called open-air laboratories across Europe. The relationship between temperature and daily-deaths has been examined using  a poisson regression model combined with a distributed-lag nonlinear model (DLNM). We computed the absolute excess (numbers) and relative excess (fraction) deaths owed to temperature or relative risk (RR) of mortality by comparing the extremely hot temperature (99^th percentile) with the minimum mortality temperature (MMT). Total heat ascribed mortality is given by the sum of the contributions from all the days of the time-series, and its ratio with the total number of deaths. Significant and non-linear associations between temperature and daily-deaths were noticed. The overall cumulative RR at the extremely hot vs. MMT was 1.292 (95% CI: 1.251–1.333). The results of this study can help in location-centric heat management action plans to certain areas at most risk.

Acknowledgements: This work is supported by the European Union's Horizon 2020 research and innovation programme; funded by and carried out within the framework of OPERANDUM project (Grant no. 776848).

Key words: Heatwaves, climate change, mortality, DLNM, risk.

How to cite: Sahani, J., Debele, S., Di Sabatino, S., and Kumar, P.: Heat ascribed mortality in southeast England, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19039, https://doi.org/10.5194/egusphere-egu2020-19039, 2020.

As a representative example of an inland water system in northern Europe the Lake Puruvesi tends to suffer from nutrient and loads. Surface runoff caused by extreme precipitation or excessive, rapid snow melt produce nutrient leaching especially from heavily managed forests. Citizen science has potential to address to risk of eutrophication of Lake Puruvesi. Firstly, forest owners need to be engaged to the project to co-design and co-develop nature-based solutions including information about forest management options to reduce nutrient leaching. Secondly, to improve understanding and modelling  standard observational network should be enhanced. The extreme precipitation in the area is monitored throughout the year with, in particular, for this project established automatic precipitation station. Additionally, during the winter season a group of citizen volunteers measure manually snow depth and snow density in the catchment area of Lake Puruvesi. The precipitation and snow data collected with in-situ and satellite measurements are analyzed to indicate the relationships of the nutrient flows and precipitation in the area. Here we present the preliminary results from the measurement campaign from the period January-April 2020.

How to cite: Drebs, A., Jantunen, R., Mäkelä, A., and Tuomenvirta, H.: Snow observations in Finland in support of designing nature-based solutions – from citizen observations to satellites, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22556, https://doi.org/10.5194/egusphere-egu2020-22556, 2020.

In the framework of the OPERANDUM (OPEn-air laboRAtories for Nature baseD solUtions to Manage environmental risks) project, modelling the effect of the Nature Based Solutions (NBS) on selected open-air laboratories plays a determinant role. In this work, we focus the attention on the Vögelsberg (Tyrol, Austria) landslide case study, located in the municipality of Wattens. The 0.25 km² active part of the slope shows annual movement rates in the order of 3.5-6 cm/a. Recent studies provided evidence that the motion is mainly driven by variations of the groundwater level. The latter are related to prolonged moist periods during which excessive rainfall or snow melt water can infiltrate and act on the geo-hydrological system. With the aim of enhancing the slope stability employing NBS, a detailed analysis of the hydrogeology and the slope characteristics have been carried out, obtaining the required technical parameters describing the involved soil material. Furthermore, a slope stability analysis by means of different numerical models has been performed. Results prove that variations of the groundwater level in the range of 1-2 m can strongly affect the stability of the slope. Thus, specific NBS should aim at reducing the amount of infiltrating water. Examples of such NBS include the adaptation of forest management and land use planning, the introduction and re-activation of drainage channels and the sealing of leaky streams and channels. Beside the effects of the variation of the groundwater level, results have proved that the slope could fail under the action of a moderate seismic load. In this scenario, it is likely that the effects of the NBS would be insufficient to maintain the slope intact.

How to cite: Tinti, S., Gallotti, G., Zieher, T., Pfeiffer, J., Zaniboni, F., Rutzinger, M., and Di Sabatino, S.: Modelling the effect of Nature Based Solutions on slope instability, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9867, https://doi.org/10.5194/egusphere-egu2020-9867, 2020.

There is growing recognition that using the properties of nature can help provide viable and cost-effective solutions to a wide range of societal challenges, including disaster risk reduction. However, nature-based solution (NBS) realization depends critically on the legal, institutional, social, political and financial conditions – that is, the governance framework - that enable the NBS policy process. Drawing from three case studies in Nocera Inferiore (Italy), Munich (Germany) and Wolong (China), we identify key governance enablers of successful NBS - that is, the contextual pre-conditions, policy processes and institutions that proved helpful or even essential for the initiation, planning, design and implementation of NBS. Results show that the most critical enablers involved governance innovation in three areas: polycentric governance (novel arrangements in the public administration that involved multiple institutional scales and/or sectors), NBS co-design (innovative stakeholder participatory processes that influenced the final NBS) and financial incentives (financial incentives for community-based implementation and monitoring of NBS). Further enablers for realizing NBS, as demonstrated in the three cases, include environmental advocacy coalition groups, along with their individual champions, and a major triggering or modelled event, which opened a window of opportunity to advocate for a nature-based or hybrid green-blue-grey solution. Findings show that the transition from grey solutions to NBS can be justified with, and contribute to, multiple global agendas and targets, including disaster risk reduction, climate change adaptation, halting biodiversity loss and sustainable development.

How to cite: Martin, J. G. C., Linnerooth-Bayer, J., Scolobig, A., and Liu, W.: Catalyzing innovation: governance enablers of nature-based solution success stories, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22547, https://doi.org/10.5194/egusphere-egu2020-22547, 2020.

In the Open-Air Laboratory (OAL)-Finland, Lake Puruvesi, the main land-use is forested areas, with minor areas in agriculture, and urban land-use. Activities related to these land-uses together with infrequently occurring high runoff peaks due to heavy rain events or rapid snowmelt cause nutrient (phosphorus, nitrogen) and sediment load risks and thus threaten recreation, fishing (professional and recreational) and biodiversity of the area. Various Nature- Based Solutions (NBS) are planned to reduce nutrient loading for the Puruvesi area. Modelling will be used to estimate the impact of NBSs on nutrient loading. It is important to increase understanding of the impacts of the extreme weather events on the amount of nutrient concentration in the water.

According to model simulations the nutrient load increases during the years with high precipitation. However, the total annual precipitation alone explain only partly the variations in the nutrient loads. The nutrient load depends also on the timing of the precipitation and the moisture condition and nutrient content of soil before the precipitation or snow melting event. Typically in Finland, the high nutrient load peaks take place during spring snow melt or after the autumn precipitation. Heavy precipitation during summer may as well induce a peak in nutrient concentrations.

Here we focus on the impacts of an extreme spring snow melt event in year 2012. In the Puruvesi region the winter 2012 was wetter than average with snow depths reaching more than 50 cm in March and lasting until mid-April. During the permanent snow cover period (31.12.2011-23.4.2012) the total precipitation was 150 mm at the weather station in the Lake Puruvesi catchment area. The snow water equivalent, i.e., the amount of water contained within the snow, is not measured in Lake Puruvesi. However, the Finnish Environment Institute produces estimates of snow water equivalents over Finland with the Watershed simulation and forecasting system (VEMALA). According to modelling the snow water equivalent was about 120 mm in mid-April in Savonlinna located about 10 km west from the Punkaharju weather station. The whole snow pack melted during 13 days (11.4.2012-23.4.2012) from 50 cm to 0 cm as the daily mean temperatures rose permanently above 0 °C. During the snow melt period the total precipitation was about 30 mm. The VEMALA model simulations show a peak of 90 µg/l in phosphorus concentrations during the snow melt in the end of April 2012. As a comparison, the drier than average year, 1993, with less snow (max depth 30 cm and slower melting) lead to a lower phosphorus concentration peak of 60 µg/l. Furthermore, the total phosphorus load in 2012 was 2.5 times higher than the load in 1993. This review demonstrates that, in extreme years, the number or effectiveness of NBS measures must be significantly increased to achieve the required reduction in nutrient leaching compared to normal or drier years.

The work is carried out as co-operation between OPERANDUM EU and Freshabit Life IP -projects.

How to cite: Korhonen, N., Tattari, S., Leinonen, A., Huttunen, M., Finér, L., Ukonmaanaho, L., and Tuomenvirta, H.: Nutrient load simulations at Lake Puruvesi, Finland: extreme case event in 2012, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4477, https://doi.org/10.5194/egusphere-egu2020-4477, 2020.

Nature-based Solutions (NBS) are being developed in variable environments to address societal challenges with use of ecosystem services. Recently there has been notable activities and progress in developing and implementing NBS in urban environments. On the other hand, NBS have “roots” in nature conservation and ecosystem services. Accordingly, the International Union for Conservation of Nature is leading the community effort to articulate a Global Standard for the Design and Verification of Nature-based Solutions.

The ongoing EU H2020 project OPERANDUM focuses on development and implementation of NBS to mitigate exposure, vulnerabilities and risks to hydro-meteorological hazards in European rural and natural landscapes. This presentation identifies and examines some of the characteristic of NBS in non-urban settings based on literature and experiences gained in the OPERANDUM project. These include, e.g. physical environment, economic and social capital as well as other resources, and legal and governance issues. Additional challenges arise from requirement to co-design of NBS with the stakeholders which can have a large diversity of societal demands for land use. The OPERANDUM project activities are discussed in relation to four approaches relevant for the OPERANDUM project: Ecosystem-based disaster risk reduction; Climate adaptation services; Ecosystem-based adaptation; Ecosystem-based mitigation.

Case – studies are being developed to document the impact of extreme events related to different hydro-meteorological hazards, e.g. floods, landslides and droughts by combining earth observation with hydro-meteorological data. The analysis is designed to mirror the role of NBS in providing multiple benefits, in particular in mitigating impacts of extreme hydro-meterological events by acting on bio-geophysical and socio-economic variables characterizing exposure and vulnerabilities.

How to cite: Tuomenvirta, H., Korhonen, N., Votsis, A., Menenti, M., Alfieri, S., Kumar, P., Renault, F., and Soini, K.: Characteristics of Nature-based Solutions in non-urban environments, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8559, https://doi.org/10.5194/egusphere-egu2020-8559, 2020.

During the past decades, risk assessment experienced increasing interest in social science but also natural science and other disciplines. At the same time, risk reduction and mitigation gained in interest from local to global level due to the shift from reactive to proactive management. Hazard and risk assessment have been approached on different levels, nonetheless, they are lacking elements such as cross-border assessment or the integration of an ecological risk assessment. One of the objectives of the H2020 Operandum project is to provide an automated science-based assessment of risk for the social-ecological system and further of the applicability and performance of Nature-based Solutions (NBS) for risk mitigation of hydro-meteorological hazards.

Within this project, an interactive webGIS analytical engine and an NBS catalogue are being developed as part of the Geospatial Information Knowledge Platform (GeoIKP). The analytical engine will encompass open Europe-wide hazard maps and link them with local high-resolution information from public and innovative data sources (e.g. Facebook). These two geo-tools are combined into a recommendation engine - NBS toolkit - trained on existing NBS. Using a holistic approach, the NBS toolkit aims at providing risk assessment and advanced recommendations on NBS usage for mitigation. For this approach, the NBS toolkit incorporates hazard and risk assessment in space and time, cost-benefit analysis, and additionally main drivers and constraints for NBS implementations as well as their geographical transferability, replicability and performance/effectiveness. 

This contribution will offer an insight into the concept and development of the NBS toolkit. Primarily, it will focus on the added value of the NBS toolkit for future nature-based implementation, risk mitigation management and decision-making at all levels. Challenges and current limitations of real-time risk assessment will also be discussed, with a focus on their implications on NBS monitoring and effectiveness.

How to cite: Ommer, J., Vranić, S., Leo, L. S., Kalas, M., Debele, S. E., Bertini, F., Montesi, D., Pavlova, I., Kumar, P., and Di Sabatino, S.: An engine for social-ecological risk analysis and NBS recommendation to support risk mitigation management, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21484, https://doi.org/10.5194/egusphere-egu2020-21484, 2020.

Abstract

Droughts are comprehensive and complex naturally occurring hazards in any climatic region around the world and often result in the loss of life and severe ecosystem damage. Drought monitoring is usually based on single-variables that may not represent the corresponding risk appropriately to its multiple causation and impact characteristics under current and future climate scenarios. In order to address this issue, the multidimensional copulas function, which is a flexible statistical tool, could be applied to develop multivariate drought indicators and solve the complicated and nonlinear associations. The aim of this paper is to develop reliable designing, monitoring and prediction indicators for the proper assessment and intervention of drought risk by nature-based solutions (NBS). Using a copula-based multivariate drought indicator (CMDI) that considers all possible variables related to meteorological, agricultural and hydrological droughts is essential for better drought risk assessment and intervention. The CMDI was developed by integrating univariate marginal cumulative distribution functions of meteorological (precipitation), agricultural (soil moisture) and hydrological (streamflow) variables into their joint cumulative distribution function. CMDI was then applied to the selected study catchment (Po Valley, Italy and Spercheios River, Greece) using hydro-meteorological data from gauging stations and ERA5 gridded data for the period 1979-2017.  The result of CMDI showed moderate, severe and extreme drought frequencies in the two selected catchments. The constructed CMDI captured more severe to extreme drought occurrence than the considered single drought indicators. This proved that the CMDI could appropriately represent the complex and interrelated natural variables. The uncertainty analysis based on Monte Carlo experiments confirmed that CMDI is a more robust and reliable approach for assessing, planning and designing a nature-based intervention for drought risk. The findings of this research can provide a reliable way to develop approaches that can be used for assessing and predicting non-linearly related variables or any risk that may occur simultaneously or cumulatively over time.   

Keywords: Drought risk; multidimensional copulas; multivariate indicators, uncertainty analysis; frequency   

Acknowledgements: This work is carried out under the framework of OPERANDUM (OPEn-air laboRAtories for Nature baseD solUtions to Manage hydro-meteo risks) project, which is funded by the Horizon 2020 under the Grant Agreement No: 776848.

How to cite: Debele, S., Sahani, J., Porcù, F., Aragão, L., Spyrou, C., Loupis, M., Charizopoulos, N., Di Sabatino, S., and Kumar, P.: A copula-based multivariate drought indicator to design and monitor nature-based solutions, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13912, https://doi.org/10.5194/egusphere-egu2020-13912, 2020.

Various frameworks for vulnerability and risk assessment of social-ecological systems (SES) to natural hazards have been developed addressing different contexts. However, none were specifically developed in the context of implementing nature-based solutions (NBS) to hydro-meteorological risks. Since the basic concepts and principles of NBS are mainly focused on ensuring balance between ecological and social benefits, the entire vulnerability and risk assessment process should focus equally on various social and ecological components of a location where an NBS would be implemented. As a part of the OPEn-air laboRAtories for Nature baseD solUtions to Manage hydro-meteo risks (OPERANDUM) project, this research proposes a conceptual framework for vulnerability and risk assessment in the context of NBS to hydro-meteorological risks. This conceptual framework is developed mainly considering the major components of the existing Delta-SES risk assessment framework (Sebesvari et al. 2016) and other similar frameworks proposed in recent studies, as well as the proposed principles for NBS endorsed by International Union for Conservation of Nature (IUCN). The major components of the framework include: (i) the exposure of SES to multiple hydro-meteorological hazards (e.g., flood, drought); (ii) vulnerability of SES that consists of ecosystem susceptibility, social susceptibility, ecosystem robustness, and coping and adaptive capacity of the social system; (iii) risks in the NBS project site determined by the combination of hazard exposure and vulnerability; and (iv) the impacts of hydro-meteorological hazards on the SES surrounding or within the NBS project site. While the basic space of risk assessment would be the NBS project site (usually at the local level within sub-catchments) with specific SES characteristics, this framework also reflects the interrelationships between ecosystem and social system as well as the effects of multiple hazards and risks at local up to the global scales. The framework also considers the changes over time that would capture the maturation time lag of the ecological components of an NBS, as well as the sustainability of the system with the intervention of NBS and other risk reduction measures. An indicator-based risk assessment approach can be used to operationalize the framework. To facilitate that, an indicator library has been developed comprising of indicators for different exposure and vulnerability components of the framework. The proposed framework can be applicable to any geographical conditions where an NBS project is to be implemented to reduce hydro-meteorological risks. The framework can also be tailored for other natural hazards (e.g. geological hazards like earthquake) and anthropogenic hazards (e.g. pollution). We will explain the conceptualisation process of the framework and of the indicator library and how these will be tested within the OPERANDUM project in the context of NBS implementation.

Keywords: Nature-based solutions, risk assessment framework, hydro-meteorological hazards, social-ecological systems 

Reference:

Sebesvari, Z., Renaud, F. G., Haas, S., Tessler, Z., Hagenlocher, M., Kloos, J., ... & Kuenzer, C. (2016). A review of vulnerability indicators for deltaic social–ecological systems. Sustainability Science, 11(4), 575-590.

How to cite: Shah, M. A. R., Renaud, F. G., Wild, A., Anderson, C. C., Loupis, M., Panga, D., Stefanopoulou, M., Polderman, A., Pouta, E., Votsis, A., Thomson, C., Munro, K., Basu, B., Pilla, F., Pulvirenti, B., Toth, E., Domeneghetti, A., and Sabatino, S. D.: A conceptual framework for vulnerability and risk assessment in the context of nature-based solutions to hydro-meteorological risks, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20403, https://doi.org/10.5194/egusphere-egu2020-20403, 2020.

Nature-based solutions (NBS) are increasingly being promoted as a means of reducing water-related risks, particularly flood risks. These solutions can also generate a wide range of co-benefits (e.g., climate regulation, air quality regulation, reduction of urban heat islands), and may pose some constraints in contexts with high population growth and urban development. Understanding and evaluating these co-benefits and constraints can be a lever to facilitate the implementation of these solutions.

We implement a Discrete Choice Experiment survey in the Lez catchment (France) to assess residents’ preferences for different types of NBS and levels of implementation and to evaluate the monetary value of NBS co-benefits. We consider two types of NBS: i) the conservation of natural and agricultural land (by limiting urban sprawl) and ii) the introduction of green infrastructure into the city.  

The results obtained from 400 households living in the Lez basin show that people associate many co-benefits with NBS and that these co-benefits are greater than constraints. The econometric analysis reveals that respondents prefer the most ambitious levels of NBS implementation. The mean overall amount residents are willing to pay for the co-benefits generated by NBS are estimated between 133€ and 178€ household/year depending on the NBS types and levels of implementation. Results also show significant levels of heterogeneity of the preference for NBS between respondent types.

This analysis confirms that people attach an economic value to the co-benefits associated to NBS primarily aiming at reducing flood risk. It gives insights to understand i) which category of population is more or less in favour of different NBS solutions and ii) which co-benefit is particularly influencial in the value granted by the population to the proposed NBS strategies. This application of the Choice Experiment methodology is one of the first application of the methodology to the evaluation of NBS. This work was carried out as part of the EU H2020 NAIAD project.

How to cite: Hérivaux, C. and Le Coënt, P.: Preferences for nature-based solutions aiming at reducing flood risks. Results of a Discrete Choice Experiment in the Lez catchment (France), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22529, https://doi.org/10.5194/egusphere-egu2020-22529, 2020.

Extreme hydro-meteorological events are often defined by the statistical analysis of some parameter that measures the strength of the event over a long enough time series. The parameter could refer to the intensity of the event in terms of energy or to the impact of the event on the environment. This attribution becomes even more relevant when used as reference for future climate projections, suggesting a possible increase in the number of extreme events considering the attribution applied to the past database. 
In the literature concerning storm-surge, the use of significant wave height (Hs) percentiles to define thresholds of an extreme event is a common practice when dealing with sufficiently long datasets. Usually, this value ranges from 90th up to 99.5th trying to highlight about 3-6 Hs peaks per year. But, in fact, thresholds should provide a benchmark for how much a region can withstand an extreme event. The Italian coast of the northern Adriatic is recently increasing its sensitivity to such episodes, that threaten one of the most active touristic hub of Italy, the highly valuable Po Delta UNESCO Biosphere Reserve and city of Venice fragile structure. Recently in late 2019, a strong event hit Venice with high tides flooding the city's main monument, St. Mark's Basilica, for the 6th time in 1200 years, with levels very similar to the worst event in history in 1966. 
Attempting to better understand the distribution of these extreme events throughout last decades and how reanalysis products can be useful for storm-surge studies, this paper presents a climatological comparison of significant wave height data extracted from ECMWF ERA5 against the entire historical series available to the Nausicaa wave buoy. This station, owned and managed by ARPAE, is located about 8 km offshore the Municipality of Cesenatico, where the seabed is about 10m, and since 2007 has been used to monitor and prevent sea level related events. In the last 12 years, at least 10 extreme events have been reported based on hourly measured data in Nausicaa and the damage observed along the coast, allowing the local authorities to define Hs thresholds as 1.5 m to significant events and 3.0 m for extreme events. However, analysing the measured data in this period, at least 26 events that exceeded the 3 m threshold were observed, representing the percentile 99.81th of the historical series, whereas only 10 storm-surge events resulted in damage to cities or environmental protection areas. When analysing Hs extracted from ERA5 at the nearest grid point to Nausicaa (~ 30 km) for the same 26 events, all events were correctly identified by reanalysis and represented with an averaged correlation of 0.96. For Hs series extracted from ERA5, values above 3 m reached the 99.83rd percentile for the same period from 2007 to 2018, and 99.84th when expanded to the last 30 years (since 1989), showing that, although quite restricted, the 99.8th percentile seems to be a good value for identifying extreme events of storm-surge in the northern Adriatic Sea.

How to cite: Porcu, F., Aragão, L., Aguzzi, M., Valentini, A., Debele, S., Kumar, P., Loupis, M., Montesarchio, M., Mercogliano, P., and Di Sabatino, S.: Extreme wave events attribution using ERA5 datasets for storm-surge studies in the northern Adriatic sea, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19443, https://doi.org/10.5194/egusphere-egu2020-19443, 2020.

The main target of this study is to evaluate the Cyclone Detection and Tracking Methods (CDTM) using the ECMWF ERA5 dataset, state-of-the-art in reanalysis models, to identify the main cyclogenesis zones and cyclone tracks inside the Mediterranean region during a climatological period. Several studies based on ECMWF analysis and reanalysis (ERA40 and ERA Interim) datasets indicate a large divergence related to the average number of cyclones passing through the Mediterranean region by year. However, the majority agrees on the most important cyclogenesis areas, seasonality variation of the number of cyclones, and trends of cyclone track. In general, the differences between those methodologies concerns to the meteorological variable used to detect cyclones and the metric used to define its intensity. Nevertheless, spatial and temporal resolutions were fundamental to achieve the results, since the most advanced dataset used in the literature presented relatively low values ​​such as 1.125°x1.125° and 6h, respectively. Past studies reported that these values ​​were already high enough to produce numerical noises. Here, the geopotential height at 1000 hPa (Z1000) was used, with horizontal spatial resolution of 0.25°x0.25° and time resolution of 1h, to identify the local minima for each time step (hereafter, candidates), and filtering those with negative gradients of Z1000 within a radius of 1000 km to exclude candidates associated with thermal lows or geopotential troughs.
Following the literature, the domain for Mediterranean region was defined by the area within 9°W to 42°E, and 27°N to 48°N, where were considered only cyclones with at least one tracking point inside the domain. Also, the results were produced for the period 1979-2008 using two types of input data: (Model I) ERA5 data with resolutions reduced to 1.5°x1.5° and 6h, as well as the main previous studies; and (Model II) full-resolution ERA5 data. As expected, Model I results were very similar to those found in the literature in all aspects (number of cyclones, seasonal distribution, areas of cyclogenesis and tracks). On the other hand, since the use of higher resolution data provides greater spatiotemporal detailing of the climatological period, the results of Model II presented a total number of cyclones substantially higher than that of Model I (~25%), but still within the range described in the literature. The models indicated more frequent cyclones during the spring months with maximums in April (Model I) and May (Model II). An interesting point highlighted in other studies but not observed in their results, is an increase in cyclone frequency between August and October, captured in both Models I and II and more evident in Model II. An explanation is found in the greater number of short-life cyclones, which act in relatively narrow areas intangible to datasets with limited resolution.

How to cite: Aragão, L. and Porcù, F.: Revisiting Cyclone Detection and Tracking Methods using ECMWF ERA5 dataset for climatological purposes in the Mediterranean Region, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21220, https://doi.org/10.5194/egusphere-egu2020-21220, 2020.