Southern Africa faces both severe droughts and strong floods. Communities describe how they are impacted by both extremes, but do not regard them as connected. They prepare for droughts by implementing water-saving measures and crop changes, but report doing little to prepare for floods. Governance actors instead try to manage both extremes, for example by installing dams that can capture floodwater to increase water availability during dry seasons. In the Connect4WR project, we combined community and governance interviews and workshops with scenario modelling to explore more nature-based solutions focusing on subsurface storage and infiltration. The governance actors in the four countries of the Limpopo (Botswana, Zimbabwe, South Africa and Mozambique) were keen to explore effects of afforestation, sand dams, managed aquifer recharge, and rainwater harvesting. The coupled surface-water-groundwater model we set up, showed that these measures can successfully reduce both droughts and floods. Especially measures that increase groundwater levels both increase water availability and reduce flood peaks throughout the basin. Although downstream communities benefit from the decreased flooding, they could be negatively affected if measures that increase (ground)water storage are combined with high abstraction for irrigation in the upstream part of the basin. In a transboundary river basin like Limpopo, international cooperation and information sharing is crucial. Also, these measures are often too costly and large-scale for the resource-limited rural communities, who can often only respond to extremes by relocating to less drought- or flood-prone areas. Training and government support can help with the implementation of nature-based solutions, but measures need to be resonating with local cultural practices to be adopted and effective land- and water management is important. In this presentation I will discuss the benefits and challenges related to the implementation of nature-based solutions in low- and middle-income countries with fragile populations.

How to cite: Van Loon, A., Matanó, A., Tirivarombo, S., Artur, L., Mustafa, S., Rohse, M., Day, R., and Comte, J.-C.: Exploring nature-based solutions to droughts and floods in the Limpopo basin, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11417, https://doi.org/10.5194/egusphere-egu23-11417, 2023.

Climatic extremes are the new normal for large parts of the world. Even temperate places, such as northern Bavaria, have experienced an abundance of extreme weather with significant impacts on the local ecology. Heavy torrential rainstorms are observed more often, while simultaneously, the precipitation required for a healthy ecology does not occur for increasing periods. These droughts, in combination with anthropogenic influences, have severely weakened the vitality of vast stretches of forest in northern Bavaria. In consequence, secondary pests were able to cause wide spread tree mortality. This indicates the need for innovative water management strategies to increase the resilience of forest ecosystems with regard to an increased occurrence of droughts.

This study aims at exploring the potential of nature-based solutions to increase the infiltration of surface runoff in forest in order to increase the plant-available soil moisture and therefore the drought resilience during dry periods. Specifically two measures are investigated, which alter the micro-topography of the forest floor. These are:

• “Dead-wood” left in the forest after timber-harvest and aligned along slopes to act as flow barriers during runoff events and,
• Small-scale basins of shallow depth that mimic the natural topography of the forest floor and act as retention basins.

To be able to understand and evaluate the effectiveness of the nature-based solutions and investigate the relevant hydrological and hydrodynamic processes, a small, forested slope in Northern Bavaria was modeled using an innovative coupling of the 2-dimensional hydrodynamic TELEMAC Model with Green & Ampt infiltration. In preparation of setting up the model, state-of-the-art drone LiDAR measurements were used to produce a high-resolution (10 cm resolution) Digital Elevation Model of the area. This enabled us to set up the model with a high enough resolution to capture and simulate the micro-topographic changes of the measures. We simulated various scenarios representing different implementations of the nature-based solutions and used the change of runoff coefficient as compared to the current state simulations as a measure of efficiency. In general, our findings show a clear link between the implementation of the measures and decreased runoff coefficient. While the aligning of dead wood along the slope reduced the runoff coefficient more as compared to a random distribution of dead-wood, the shallow retention-basins showed a significantly higher impact on the runoff coefficient. However, it is likely that the distribution of soil types, vegetation and soil animal activity are very crucial because they significantly affect the infiltration and therefore the efficiency of these measures for drought resilience. Theses aspects were not considered. Altogether, the results of this study should be considered as qualitative as compared to quantitative, due to the simplifications done, especially with regard to the soil and infiltration processes.

Keywords: Drought; Forest ecosystem; TELEMAC; Greene & Ampt; LiDAR

How to cite: Alcamo, L., Broich, K., and Disse, M.: Nature-based solutions for drought resilient forests, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14949, https://doi.org/10.5194/egusphere-egu23-14949, 2023.

Sustainable urban drainage systems (SUDS) have been increasingly implemented as a low-impact, cost-effective stormwater control measure (SCM). SUDS include a diverse set of infiltration-based measures designed to maintain the pre-development hydrological cycle, reduce runoff, and enhance water quality via infiltration. However, these functions are prone to deterioration during winter, especially when soil frost is present. Unlike inland cold regions, maritime cities are particularly vulnerable to the negative winter impacts due to frequent freeze-thaw cycles, rain-on-snow events, and intermittent midwinter snowmelt. To date, the hydrological efficacy of SUDS at catchment-scale under cyclical cold conditions is still lacking. The goal of this study, therefore, was to evaluate the runoff and volume reduction achieved by a SUDS network in a small, 1.5 ha catchment in Garðabær, Iceland. In addition to assessing the seasonal and spatial variability of infiltration performance of different SUDS elements with varied soil properties and vegetation covers in an urban area. To that end, a total of 18 soil water content reflectometers to measure soil temperature and moisture were implemented in three SUDS components (i.e., densely vegetated rain garden, sparsely vegetated rain garden, and a front lawn with a grass vegetation cover receiving stormwater from a roof through a drain into a soakaway) in the study area at different depths (5–20 cm). An area-velocity flowmeter was installed at the outfall of the catchment to monitor runoff from the SUDS system as well as from the impervious surfaces that include streets, parking lots, and walking paths. Preliminary assessment at the beginning of the freezing period (i.e., November and December) showed that the densely vegetated rain garden was less susceptible to frost formation (frost reached 15 cm depth; min. -1.6 °C) compared to the sparsely vegetated rain garden (20 cm frost depth; min. -3.8 °C at 15 cm). In the front lawn, on the other hand, frost penetrated down to 10 cm depth (the depth at which soil was monitored and the minimum soil temperature dropped to -5.4 °C). The preliminary results show that the SUDS system was very effective during summer/fall and successfully infiltrated a total of 58% (n=14) of the storm events, especially small events (< 2 mm). The runoff coefficient for the events that produced surface runoff ranged between 0.011 and 0.19 (n=24) with an average volume reduction of 92% of the incoming runoff. However, further assessment of the system’s efficiency in terms of volume and runoff reduction during winter is still needed.

How to cite: Zaqout, T. and Andradóttir, H. Ó.: Catchment-scale hydrological performance of sustainable urban drainage systems in a cold maritime climate undergoing soil freeze-thaw cycles and rain-on-snow events, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5220, https://doi.org/10.5194/egusphere-egu23-5220, 2023.

The Rain Garden was built as part of "Proterina 3 Evolution", a strategic project of the Interreg Maritime Italy France program, between 2018 and 2019, commissioned by the partner Città Metropolitana di Genova to the Department of Architecture and Design of the University of Genoa, with the project's scientific directors prof. Adriano Magliocco and prof. Katia Perini, involving arch. Paola Sabbion, as landscape architect and, subsequently as regards to hydrological monitoring, prof. Luca Lanza and dr. Arianna Cauteruccio.

The rain garden was built in a free area facing a school building in the municipality of Campomorone (Genoa, Italy). The goal was to verify the functioning of a NBS in a climatic context characterized by rainfall concentrated in short periods of time, with particularly dry summer seasons.

The rain garden is of the non-infiltrating type. It receives the rainwater directly and from the pavement of a parking lot. The water passes through a container equipped with an overflow and is supplied to the rain garden via a micro-perforated pipe. The Rain Garden is waterproofed on the bottom and has a drainage pipe that takes the water to the measuring device placed inside a control pit.

The pilot site is equipped with a tipping bucket rain gauge, calibrated according to the European Standard EN 17277:2019. The rain gauge provides the inter-tip time stamp as a measurement of precipitation intensity at high temporal resolution. Both direct precipitation over the raingarden area and the flow rate drained from the nearby impervious parking surface act as the forcing input. The output from the raingarden is measured using a water level gauge located in the output control pit, at a one-second resolution. The input and output measurements are then aggregated at the one-minute resolution for post-processing.

In this work, the hydrological behaviour of the raingarden is simulated using a conceptual model involving a cascade of three linear reservoirs: the first one representing the fast response of the impervious surface, the second one the shallow soil layer used by the vegetation and the third one the deep drainage layer. Each reservoir is characterized by a retention and a storage coefficient. Precipitation and outflow events recorded during one year of measurements in the wet period, from autumn to spring, allowed characterizing the hydrological performance of the system. The value of each parameter was calibrated using part of the measured precipitation and outflow events. The remaining events were used to validate the reliability of the conceptual model using the same parameters. The aim of this work is to verify the role of the implemented NBS to reduce direct runoff in an urban environment for flood risk mitigation purposes.

Results are expressed in terms of non-dimensional performance indices: flow peak attenuation, dead time and retention coefficient. The validation of the model parameters allows extending this NBS model to other sites characterized by a similar rainfall climatology. In that case, performance indices can be derived by measuring the precipitation alone.

How to cite: Magliocco, A., Cauteruccio, A., Perini, K., and Lanza, L.: Monitoring and modeling the hydrological performance of a rain garden installation for flood risk mitigation at a urban site, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5974, https://doi.org/10.5194/egusphere-egu23-5974, 2023.

Urbanization and climate change are increasing the frequency and severity of urban pluvial flooding. The traditional urban modelling approaches do not take infiltration from sealed surfaces into account, leading to an overestimation of excess runoff. Still, the conventional centralized sewage systems are often overburdened. While municipalities are taking initiatives to utilize green infrastructure as a sustainable way to manage stormwater, the performance of the implemented measures varies from region to region. This study uses the WaSim-ETH physically based hydrological model to investigate runoff and infiltration processes in urban areas and determine how much rainfall contributes to runoff and infiltrates through different types of land use surfaces. It also evaluates the efficiency of green infrastructure to reduce the generated runoff from different rainfall events. The model is applied to study areas in Berlin and Würzburg, both cities have experienced frequent pluvial flooding in the last decades.

How to cite: Dobkowitz, S. and Seleem, O.: Evaluating the impact of infiltration from sealed surfaces and green infrastructure on urban pluvial flooding, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6841, https://doi.org/10.5194/egusphere-egu23-6841, 2023.

Sponge-city sites for urban trees based on the model of Stockholm promise to improve the chances of trees surrounded by sealed or condensed surfaces for root growth and therefore vital tree development tremendously. The system furthermore helps to conquer the urban heat island effect, aids in stormwater management as an underground retention basin saving soil water for transpiration and hence supports the ambition to approach a (more) natural hydrologic cycle. The actual capacity of the system to fulfil these services is determined by a variety of design criteria which need to be optimized based on detailed knowledge about the hydrological functionality of the different elements of the system. The aim of several monitoring and modelling studies in Austria is to gain such knowledge to ensure a proper performance of the system in terms of tree growth and rainwater retention.

First of all, the substructure construction consists of unconsolidated fine substrate flushed into the voids of edged stones that serve as load-bearing structure, assuring root-favouring pore distribution. Technical components like an inlet and surface water distribution system accompany the substrate. Further influencing parameters are e.g. properties of the existing substrate underneath, design of urban surface as well as origin and treatment of fed surface water. Based on monitoring sites in the shape of lysimeters, field scale projects in real urban settings, and laboratory experiments, modelling approaches for the hydrological functionality of the sponge-city systems are generated. Crucial system elements and target values for design properties are derived from these simulations. In the longer term, the results should serve as a supportive planning tool for engineering projects in urban environments.

How to cite: Zeiser, A., Rath, S., Strauss, P., and Weninger, T.: Hydrologic characterization of sponge-city systems for urban trees based on monitoring and modelling, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14281, https://doi.org/10.5194/egusphere-egu23-14281, 2023.

During COP14 in 2022, Ramsar Convention commended 25 cities around the world for their efforts to protect urban wetlands. With the development of cities and the increase in land demand, the trend is to reduce the number of open blue spaces. Yet when preserved and sustainably used, urban nature-based solutions in the form of constructed wetlands could provide water management benefits including water quality regulation and flood mitigation. However, these water management benefits have rarely been evaluated at a catchment scale, and the mechanisms behind them are not fully understood, both of which hinder effective integrated constructed wetlands planning. We aim to explore the impact of wetland changes on water quality and quantity at the catchment scale. This study firstly evaluates the benefits by analysing the monitoring water quantity and quality datasets before and after the wetland construction in Enfield catchment, London. To understand the mechanisms behind the benefits, we build a Water Systems Integration Modelling framework (WSIMOD) to simulate the catchment-scale water cycle. This model is validated against monitoring river flow and water quality data. The constructed wetlands are then conceptualised and integrated into the WSIMOD, and their interactions with the catchment water cycle are simulated. Scenarios are constructed to analyse the impacts of different configurations and sizes of the constructed wetlands on the catchment water cycle. The results show that urban wetlands play a role in flood detention and water quality purification of watershed water resources at the catchment scale. Scattered small wetlands can more effectively reduce the impact of a flood under the same total wetland area. The results provide useful insights into the planning of constructed wetlands for maximising the water management benefits at a catchment scale. Future studies could focus on representing the interaction between the quantity and quality of water in a wetland with biodiversity and leveraging this representation to design interventions to improve biodiversity.

How to cite: Peng, F., Liu, L., Gao, Y., Krivtsov, V., Dobson, B., and Mijic, A.: Evaluating the impact of urban wetlands as nature-based solutions at the catchment scale, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6780, https://doi.org/10.5194/egusphere-egu23-6780, 2023.

Nature-based solutions (NBS) have co-benefits for water availability, water quality, and flood management. However, searching for optimal integrated urban-rural NBS planning to maximise co-benefits at a catchment scale is still limited by fragmented evaluation. This study develops an integrated urban-rural NBS planning optimisation framework based on the CatchWat-SD model, which is developed to simulate a multi-catchment integrated water cycle in the Norfolk region, UK. Three rural (runoff attenuation features, regenerative farming, floodplain) and two urban (urban green space, constructed wastewater wetlands) NBS interventions are integrated into the model at a range of implementation scales. A many-objective optimization problem with seven water management objectives to account for flow, quality and cost indicators is formulated, and the NSGAII algorithm is adopted to search for optimal NBS portfolios. Results show that rural NBS have more significant impacts across the catchment, which increase with the scale of implementation. Integrated urban-rural NBS planning can improve water availability, water quality, and flood management simultaneously, though trade-offs exist between different objectives. Runoff attenuation features and floodplains provide the greatest benefits for water availability. Regenerative farming is most effective for water quality and flood management, though it decreases water availability by up to 15% because it retains more water in the soil. Phosphorus levels are best reduced by expansion of urban green space to decrease loading on combined sewer systems, though this trades off against water availability, flood, nitrogen and suspended solids. The proposed framework enables spatial prioritisation of NBS, which may ultimately guide multi-stakeholder decision-making, bridging the urban-rural divide in catchment water management. 

How to cite: Liu, L., Dobson, B., and Mijic, A.: Optimisation of Urban-Rural Nature-Based Solutions for Integrated Catchment Water Management, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10360, https://doi.org/10.5194/egusphere-egu23-10360, 2023.

The H2020 project PHUSICOS has from 2018-2022 aimed to demonstrate how nature-based solutions (NbS) reduce the risk of extreme weather events in rural areas and mountain landscapes. Mountains amplify risks and therefore the impacts of extreme hydro-meteorological events such as flooding and landslides in mountain areas often affect entire river basins. However, NBS in rural areas and mountain regions have not received the same amount of attention as urban areas. This presentation highlights the lessons learned in order to tackle the challenges of selecting, designing and implementing NbS at the landscape spatial scale in rural areas.  

The PHUSICOS case study sites in Norway, France, Spain, Italy, Germany and Austria represent a broad range of natural hazards, including snow avalanches, erosion, rockfall, flooding and debris flows. The demonstrator sites have undergone a co-creation process with stakeholders to select and plan the NbS interventions. The specific location and NbS selection were based on a rigorous process considering the following selection criteria: risk reduction, technical feasibility, co-benefits, effectiveness, efficiency, potential negative impacts, stakeholder involvement, and compliance with international and EU agreements and directives.

Innovation actions have framed the project activities as an approach to fill NbS knowledge gaps. These innovation actions have included: service innovation to engage stakeholder participation through a Living Labs approach, technical innovation to design an NbS assessment framework in the context of natural hazard risk mitigation to document the effectiveness of NbSs, governance innovation to explore planning and policy frameworks as enablers for the design and implementation of NbS, learning arena innovation to facilitate knowledge exchange through Virtual Reality and Serious Gaming as training programs as well as product innovation establishes an evidence-base and data platform for NbS in mountains.

For example, the assessment framework as a flexible disaster risk management support tool for NbS is viewed as especially relevant. It has been applied to three different NbS interventions to document the baseline scenario and subsequently compared to the NbS design scenario. After completion, the assessment framework will be used to develop the monitoring programs to assess the long-term effectiveness of the NbS interventions. Improved processes and services related to governance innovation outputs focus on exploring ways to improve the planning policy and implementation mechanisms for sustainable use and management of land, water, and natural resources in rural areas and their impacts at the local and wider watershed scale. The most critical governance innovation enablers for successful NbS interventions include polycentric governance arrangements in public administration, participatory co-design processes, as well as financial incentives.

The different innovation actions will be further showcased to share project outputs and outcomes, to reflect on the lessons learned as well as to weigh in on their significance towards long-term impacts.

How to cite: Oen, A., Kalsnes, B., Solheim, A., Capobianco, V., Strout, J., and Nadim, F.: PHUSICOS – Nature-Based Solutions to Reduce Risk in Rural Areas and Mountain Landscapes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9957, https://doi.org/10.5194/egusphere-egu23-9957, 2023.

Natural disasters are creating a major collapse in human existence. Among the many, drought is becoming more frequent and intense. Therefore, mitigation/adaptation measures have to be set to reduce the impact. This can be achieved via the application of Nature-based solutions (NBSs). This concept is now gaining more attention than ever but with fewer applications. The primary goal of this review paper is to analyze the different NBSs targeted for drought impact mitigation. The study constitutes the application of NBS at a global, continental and regional scale. Extensive literature was made to assess; NBS type, location, start and ending period of implementation, status, and level of effectiveness, recommendations set by researchers, and insight for future applications.

The comprehensive review revealed that there are only a few scientific publications, hence, grey and non-scientific literature need to be included. Only four papers included a quantitative assessment for evaluating the effectiveness of NBS targeting drought. However, the continental and regional performance of NBS is not mentioned. Therefore, a common effectiveness evaluation framework shall be created to give policymakers a clear view of the different NBS’s. Furthermore, a more collaborative approach, including different stakeholder groups, is recommended, with specific attention to the local communities. In Flanders, most projects are in the pilot project stage. Moreover, the few successfully implemented projects are only very local and have a long realization time which the earlier limits to acquire visible impact at a larger scale. Finally, the loss of wetlands at a global scale and in Flanders (70% are lost), increases the vulnerability of catchments to drought. Therefore, future research should increase the evidence base and implementation of NBS, such as wetlands, in Flanders.

How to cite: Yimer, E. A., De Trift, L., Nossent, J., and Van Griensven, A.: Drought mitigating nature-based solutions: a critical state-of-the-art review at global and regional scales, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7494, https://doi.org/10.5194/egusphere-egu23-7494, 2023.

The U.S. Army Corps of Engineers (USACE) has a major responsibility for the regulation of the Nation’s streams, rivers, and waterways. This often requires developing water quality models to resolve issues and concerns with regard to the environment and ecosystems. USACE Engineer Research and Development Center (ERDC) is currently developing an Eco-Hydrology Engineering Design Tool supported by years of research and development. This tool development integrates ERDC’s Gridded Surface Subsurface Hydrologic Analysis (GSSHA) model and the Corps Library for Environmental Analysis and Restoration of Watersheds (ClearWater), a suite of water quality and ecosystem models.

Weather is not the only cause of flooding, stream erosion, and pollution. These problems usually occur due to human impacts on watersheds, including urban development, construction activities, hydrologic modifications, forestry, mining, and agricultural practices.

To help evaluate the impact of these serious economic and environmental issues, experts in watershed, riverine, and reservoir engineering at the ERDC developed a suite of water quality, contaminant, and vegetation modules that can be integrated with existing hydraulic and hydrologic models.

ClearWater, developed by the ERDC, LimnoTech, and Portland State University, is a library of environmental simulation software that leverages capabilities of existing water resource simulation models (e.g., HEC-RAS-1D/2D,  HEC-ResSim, GSSHA, AdH, and SWAT) to assess environmental impacts (e.g., changes in water temperature and constituent concentrations) and design solutions (e.g., constructed wetlands) to manage (e.g., modifications to reservoir operations rules) and restore aquatic ecosystems (e.g., fisheries and bird habitat). The following water quality modules are included: NSMs (Nutrient Simulation Modules I and II), TSM (Temperature Simulation Module), MSM (Mercury Simulation Module), CSM (Contaminant Simulation Module), GCSM (General Constituent Simulation Module), SSM (Solids Simulation Module), and RVSM (Riparian Vegetation Simulation Module).

This presentation will discuss current development efforts and future directions in support of an Eco-Hydrology Engineering Design Tool to support U.S. Army Corps of Engineers (USACE) ecosystem restoration and management.

How to cite: Steissberg, T., Johnson, B., and Zhang, Z.: Eco-Hydrology Engineering Design Tool - ClearWater Capabilities - General Constituents, Nutrients, and Contaminants, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12470, https://doi.org/10.5194/egusphere-egu23-12470, 2023.

Nature-Based Infrastructure (NBI) should be designed to evolve over time with the ability to adapt to changing conditions while providing ecosystem benefits to form culturally valuable landscapes. There are substantial differences between NBI and traditional infrastructure - whose forms specifically do not change over time and do not migrate or evolve. Given these differences as well as the substantial operational scale of NBI, how do we monitor and determine their management needs?

Professors Basener and Luegering’s research examines the role of plants as vital elements of NBI, whose capacity to indicate climate change impacts as well as respond to varying conditions through existing genetic capacities such as rapid resprouting, rhizomatous or tillering root systems, present an immense opportunity to track, induce and manage these changes.  With plants at the center of the research, our work builds on emerging remote sensing techniques, to develop ‘Fundamental Signatures’ (FS), which are signatures whose development methods anticipate atmospheric material interference, increase and vary resolution, and increase seasonal collection frequency with sensitivity towards species habits and growth patterns. FS engage the chemistry and geometry of plants through the intentional usage of emerging technology in the form of Hyperspectral and LiDAR sensors.

We argue that the 2020 spectral research survey performed by Hennessy, Clarke and Andrew Hennessy in Hyperspectral Classification of Plants: A Review of Waveband Selection Generalizability, points to a need for a greatly expanded capture and classification of signatures associated with seasonal variation as well as environmental disturbance.  As such, we are working to develop controlled studies at our test plots at the University of Virginia’s Morven Sustainability Lab. With these test plots, we can track spectral changes with regular intervals, but further, we will create controlled inundations with salt and fresh water as well as manipulate the pH and soil composition to track a full range of spectral signatures within each species. We have teamed with the United States Department of Agriculture Natural Resource Conservation Service (USDA-NRCS) to assist in study development as well as plant and knowledge exchange.

Our scale of study stretches from the single plant and test plot scale (CM scale) to the Chesapeake Bay (KM scale). As we develop Fundamental Signatures for indicator and disturbance invigorated species, we will begin to test them against seasonal large-scale data collections performed by the University of Vermont, including LiDAR and Hyperspectral data collected via manned aircraft. At the scale of the Chesapeake Bay, we can study the effectiveness of fundamental signatures in identifying existing plant communities as well as the identification of stressors through variegated portions of the fundamental signature.

The project continues to work towards several key outcomes, including the construction of a public fundamental signature library, the development of workflows for incorporating and updated landcover and Manning’s classifications for hydrodynamic modeling and design studies as well as field techniques for the propagation and manipulation of plants in Nature-Based Infrastructure. 

How to cite: Luegering, M. and Basener, W.: Monitoring Landscape Change: Fundamental Spectral Signatures and the Adaptive Management of Nature-Based Infrastructure , EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1922, https://doi.org/10.5194/egusphere-egu23-1922, 2023.

Natural hazards such as typhoons and earthquakes caused by climate change cause enormous damage to the social-ecological system and result in the degradation of ecosystem services. This has suggested the necessity of considering the concept of resilience along with the limitations of existing methods in disaster management and has been linked to restoration plans connected to nature-based solutions. The Republic of Korea suffers from natural disasters caused by typhoons and torrential rains every summer and the damage is worsened because of insufficient spatial management and the failure to predict disasters. Therefore, to cope with these damages and maintain ecosystem services, a nature-based restoration plan should be presented using the concept of resilience. In the process, it is necessary to understand the changes that have happened in ecosystem services over time and plan a space that can respond to natural disasters. The purpose of this study is to simulate changes in ecosystem services for natural disaster damage through spatial-temporal models and present the improvement effects of ecosystem services through nature-based restoration scenarios. Accordingly, we first searched for areas to which the resilient ecosystem service restoration planning could be applied within Pohang, which suffered significant flood damage throughout 2022. Then, a spatial-temporal model of the target area was constructed to simulate changes in the ecosystem services due to floods. Finally, the ecosystem service improvement effect of the spatial-temporal simulation model was analyzed by constructing and applying a nature-based restoration scenario. Based on the results of this study, a nature-based restoration plan was conceived of as a method to improve ecosystem services for the long term by simulating changes in the target area affected by natural disasters in terms of time and space. In addition, by presenting the preceding process as a nature-based restoration plan, it is possible to maintain resilience to the damage caused by natural disasters in terms of the social-ecological system.

This research was supported by Basic Science Research Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Education(NRF-2021R1A6A3A01087973). This research was also supported by OJEong Resilience Institute (OJERI).

How to cite: Song, K. and Chon, J.: Nature-based Restoration Planning using Spatial-Temporal Simulation Modeling, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12565, https://doi.org/10.5194/egusphere-egu23-12565, 2023.

In recent years Nature-based Solutions (NbS) have received increasing attention in coastal areas due to their ability to counteract Hydro-Meteorological Hazards (HMHs) and adverse climate change effects through habitat restoration and the re-establishment of Ecosystem Services (ES). Regardless of the wide adoption of NbS, there remain gaps and barriers in the effective uptake and implementation. There is an urgent need to define the specifics of NbS outcomes, measures of success and appropriate evaluation metrics. To bridge this knowledge gap this review focuses on: i) the terminology of NbS applied in coastal archetypes; ii) the ecosystem services delivered; iii) the HMHs targeted by NbS; and iv) the effectiveness indicators and metrics applied to monitor the impact of NbS implementation, including the tools and technologies employed. The NbS terminology applied addresses a range of different approaches included under the umbrella term NbS, e.g., building with nature, nature-based adaptation, or mitigation, and ecosystem-based management. Yet most of the included approaches mention the provisioning of ES as part of the main objective, relying on habitats and ecosystems to provide these services. In the scope of this paper 87.1% of the included ES can be attributed to regulating services such as reduction of erosion rates, coastal protection, carbon sequestration and water quality improvement.  The ES also clearly align with the climate change hazards addressed by NbS which include, e.g., flood and erosion risk, sea level rise, eutrophication, and extreme weather. These hazards are addressed through the implementation of NbS which aim to, e.g., reduce wave energy, anticipate storm surges, achieve good ecological/environmental status of water, re-establish carbon sinks and mitigate storm risk. To evaluate the effectiveness of NbS in counteracting these hazards and mitigate the impact of climate change this work identified 28 indicators. The indicators reflect mainly habitat characteristics and ES, e.g., geomorphology, vegetation cover and composition, risk reduction, carbon sequestration, and storm surge attenuation, complemented by socio-economic indicators such as willingness to pay and stakeholder perception. They are supported by multitude of metrics, evaluated through a variety of monitoring methods encompassing historical records (to create a baseline using, e.g.,  salinity records, seagrasses, vegetation status, or habitat size), questionnaires (to evaluate stakeholder values), in-situ measurements and remote sensing (to assess change in, e.g., bed level dynamics, vegetation presence, carbon stock, bird species, and marsh surface following NbS interventions) and modelling (the impact of NbS through, e.g., UVVR, morphology, vegetated leading edge, and habitat distribution). The results of this review will support the upcoming monitoring activity of saltmarsh restoration in the Venice lagoon (Italy) as part of the REST-COAST project and will pave the way for the creation of a methodological framework to systematically evaluate NbS effectiveness under current and future climate change scenarios. The project leading to these results has received funding from the European Union’s Horizon2020 research and innovation programme under grant agreement No 101037097.

How to cite: Horneman, F., Torresan, S., Furlan, E., Ngoc Nguyen, D., Telke Asresu, A., and Critto, A.: Indicators and metrics to evaluate the effectiveness of nature-based solutions for climate risk management and adaptation: A systematic review, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8034, https://doi.org/10.5194/egusphere-egu23-8034, 2023.

Increased flooding frequency and intensity threaten vulnerable populations’ lives and livelihoods worldwide. Fitting into the preparedness and mitigation phases of the Disaster Risk Management framework used by humanitarian and conservation organisations, Nature-Based Solutions (NBS) have been advanced as effective alternatives to traditional grey infrastructures in order to mitigate flooding impacts. By reproducing natural processes, NBS have shown to provide multiple environmental, social, and economic benefits in addition to their technical performance in mitigating floods. However, a framework to systematically assess these co-benefits is not readily available, which is an obstacle to the effective implementation of NBS on a larger scale. This paper develops such a framework using a Systematic Literature Review (SLR) based on the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) method. The framework includes a set of descriptors to characterize and analyse NBS consistently. These include:

• Type of NBS;
• Type of protection area (coastal, urban, rural, mountainous, riverine);
• Provided environmental/technical/social/economic benefits;
• Location of applicability;
• Scale of implementation;
• Inclusion of stakeholders’ preferences for NBS implementation.

The  SLR is shaped using a combination of scholarly literature (via Web of Science) and grey literature from reputable organizations in the NBS domain and beyond, including the WWF Nature-based Solutions Accelerator, the United Nations Office for Disaster Reduction, the Disaster Risk Management Knowledge Centre, and the Geneva Environment Network. The resulting framework can support decision-making and facilitates the deployment of sustainable infrastructure. The Red Cross Red Crescent Movement and WWF will test the framework in a case study in the Zambezi river basin in Zambia.

How to cite: Gallois, L., van den Homberg, M., and Cinelli, M.: Multiple criteria-based assessments of Nature-Based Solutions for flood management: a review, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9844, https://doi.org/10.5194/egusphere-egu23-9844, 2023.

Fluvial floods in recent years (e.g., 2002 and 2013) have caused high financial losses in Germany. Floodplains are under extensive use and dikes disconnect two thirds of natural flood retention areas from rivers. Moreover, floodplains serve as hotspots of biodiversity and floodplain habitats as well as ecosystems are categorized as endangered. Additionally, the goal of the German National Strategy on Biodiversity in increasing retention areas along rivers by at least 10% by 2020 failed. In summary, urgent actions need to be taken to reduce flood risk on the one hand, and increase floodplain area for ecological improvement – often synergies are not considered. Dike Relocation (DR) or levee setback is considered as nature-based flood protection measure whereby flood water levels can be lowered by reconnecting floodplain areas to rivers and improving nature conservation. Although DRs are being implemented already, an integrated and systematic approach is needed to consider the synergies between fields, nature conservation and flood protection.

Using dike lines, Basic European Assets Map (BEAM), Natura 2000 protected sites, and EU Copernicus land use map, a GIS-based method was developed. Four criteria were considered to evaluate effective DR; (1) The narrowness of flood channels, (2) flood-exposed assets and population, (3) floodplain habitats, and (4) urban land use and infrastructure behind the dikes. Narrow width in flood channels (between dike lines) were identified as bottlenecks. Using BEAM, flood-exposed population and asset values were calculated upstream of the identified bottleneck. The area behind dikes was searched for Special Areas of Conservation (SACs) with typical floodplain habitats. By ranking and rescaling, indices were provided for each criterion. The indices were combined with equal weights to reach DR effectiveness index. The share of urban land use and transport infrastructure was calculated behind the dikes, and DRs were grouped based on the potential of socio-economic conflicting interests.

The developed method was applied to the German part of the river Elbe. Along the 195 km river reach between Tangermuende and Geesthacht, 29 critical bottlenecks were identified. Because of high urban land use and existing transport infrastructure behind the dikes, no DR is possible at 13 of those bottlenecks. As an example of recommended DRs, the highest effectiveness index was reached for a 72% width contraction and flood-exposed assets of 16 million Euro/km² with high share of habitat area behind the dikes (93%). The results were confirmed by a comparison of this approach with the German Federal Institute of Hydrology (BfG) 2D hydraulic analysis of bottlenecks at the Lower Middle Elbe.

The GIS-based method can be used especially in the initial phase of decision making instead of time-consuming hydraulic models. Hereby, priority is given to DRs with higher synergy and low socioeconomic restrictions. Application of freely available data makes the method transferable to other European countries.

How to cite: Kazemi, H., Natho, S., and Thieken, A.: GIS-based identification of effective dike relocations: considering the synergy between nature conservation and flood risk reduction, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5241, https://doi.org/10.5194/egusphere-egu23-5241, 2023.

Tonkin, B.R^a., Marti-Cardona, B^a., Hughes, S.J^a., Ru, T^a., Philpott, N^b.

^a Civil and Environmental Engineering Department, University of Surrey, UK.

^b Environment Agency, England.

b.tonkin@surrey.ac.uk

Nature-based solutions (NBS) are increasingly being recognised as a tool for flood mitigation, particularly relevant in the face of increased storm severity due to climate change. The simulation of NBS functioning is of great interest for their effective location and design, and there are substantial ongoing efforts in developing strategies to underpin their catchment scale modelling.  Leaky Barriers (LB) are a type of NBS interventions which consist of placing logs across a channel to hold back runoff during storm events and to slow down its travel. Despite their common adoption in the UK, there are relatively few studies that have addressed the best hydraulic representations of LB’s through calibrated and validated measurements during flood events. 

This study is based within the Thames basin in the Southeast of England and encompasses the 21km² headwater catchment of the Pipp Brook. In 2019, the Environment Agency of England installed over thirty LB’s in the Pipp Brook as a trail study. Monitoring data has been continuously acquired by sensors installed at the site (water level gauges, ultrasonic flow gauge, fixed-point infrared cameras) and during periodic inspections (structural monitoring) since 2019. This enhanced monitoring programme, one of the most comprehensive in the UK, provides rigorous evidence to understand and assess the effectiveness of the NFM measures installed in the catchment. To date, this has included the capture of multiple high flow events, up to a peak magnitude of 1 in 20 years.

This research seeks to address a gap in the strategy to simulate individual leaky barriers using 1-dimensional hydraulic models. To this aim, one LB in the Pipp Brook was simulated with an industry leading hydraulic modelling software package (Flood Modeller, Version 6.10 by Jacobs) using six different 1D modelling strategies reported in the literature: i) Orifice, ii) Bridge, iii) Weir, iv) Increased roughness (Manning’s n), v) Bernoulli loss, vi) Blockage. High-flow records from a double-peak event in October 2021 were used to calibrate and assess these hydraulic representations. Upstream boundary conditions were produced by ReFH2 rainfall-runoff modelling, using the precipitation records from a nearby meteorological station.

The comparison of calibrated models to the gauged data revealed a maximum difference of circa 0.20m to the measured upstream water elevation, for a maximum water depth of 0.75m. Our results showed that the best approximation was achieved by using the bridge unit. A common approach in the literature is to represent LB’s with a high roughness coefficient (Manning’s n), which in our case resulted in the poorest performance. The results of this ongoing research will improve the ability of flood practitioners to predict the effectiveness of leaky barrier configurations in a catchment, hence informing their optimal design.

How to cite: tonkin, B.: Nature-based solutions for flood mitigation:Monitoring and modelling leaky barriers. A case study from the South East of England., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7126, https://doi.org/10.5194/egusphere-egu23-7126, 2023.

Flood is one of the most frequent and costly natural disasters worldwide. In many cases, implementing flood protection measures is limited due to land or resource availability. Natural Water Retention Measures (NWRMs), a more cost-effective approach, have recently drawn the attention of many researchers. Instead of infrastructure construction, NWRMs aim to reduce the risk of flooding and economic loss by land use and water management practices without many construction applications. Much previous literature qualitatively investigates the mechanisms of NWRMs, however, only a few focus on the hydraulic characteristic and the effectiveness of flood reduction of NWRMs. To improve the understanding of NWRMs, this study clarifies and analyzes the hydraulic performance of NWRMs. We consider the triangular inflow hydrograph based on the continuity equation with the Muskingum-Cunge method to derive the outflow of the channel, as well as the weir equation to the outflow of the retention area. Following, the continuity equations are formulated as a first-order ordinary differential equation in dimensionless form. The conceptual model built from the equations could denote the primary hydraulic mechanism in the original channel and the additional retention area. Two important parameters include the ratio of peak maximum outflow and peak inflow, and the ratio of maximum storage and total flood volume can be obtained by solving the equations. The results show that the relationship between two dimensionless parameters are nonlinear. Also, in the channel, the relationship is sensitive to the shape factor in the Muskingum-Cunge method, especially in a lower ratio of maximum outflow and peak inflow. With this model, the study following examined the different proportional of flood volume flowing in retention areas and calculate the downstream outflow. The result shows the effectiveness of flood reduction and the proportional of flood volume in retention areas are nonlinear relationships. Briefly, there is an optimal operation of NWRMs by balancing the flood volume in the river and retention could induce the minimum outflow. The findings in this study represent the hydraulic performance of NWRMs. The results can also improve the design and operation of NWRMs appropriately.

How to cite: Huang, Y.-S. and You, J.-Y.: Application Continuity Equation to Analyze the Hydraulic Performance of Nature Water Retention Measures, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4335, https://doi.org/10.5194/egusphere-egu23-4335, 2023.