S30

Riparian habitats represent an important ecosystem providing a number of functions and services that are important to humans - such as promoting biodiversity, reducing erosion risk, or transporting pollutants from the surrounding landscape into waterways. At the same time, unfortunately, it is an environment that has very often come under considerable pressure as a result of agricultural cultivation of the landscape or the development of industrial and human settlement activities. Thus, a large number of riparian ecosystems have disappeared or deteriorated. The assessment of the overall ecological status of riparian habitats is therefore an important source of information for the needs of water management and landscape planning in the riparian landscape, the aim of which should be to maintain the good status or improve the currently unsatisfactory status of these habitats. In the Czech Republic, there is not yet a comprehensive assessment procedure that takes into account not only the important sub-variables that influence the current status (e.g. the morphological condition of the watercourse or the predominant land use categories in the surrounding area), but also the potential reference status. For this reason, a tool (Riparian Habitat Quality Index) was developed by the author's team to assess the ecological status of riparian habitats. The created web platform "RipaSoft" allows streamlining the whole assessment process. Our contribution describes the assessment procedures and selected results of applying the methodology to several case study sites (small stream watersheds). The results can significantly contribute to the identification of sites suitable for the implementation of nature-based solutions aimed at mitigating vulnerability to hydrological risks (not only the risk of droughts and flash floods, but also the pollution of surface waters due to the transport of fertilizers and other pollutants from the surrounding landscape).

How to cite: Jakubínský, J., Cudlín, P., Pechanec, V., Machová, K., Cudlín, O., Štěrbová, L., Purkyt, J., and Prokopová, M.: Riparian zone assessment as a tool for planning nature-based solutions, IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-174, https://doi.org/10.5194/iahs2022-174, 2022.

Nutrient pollution is among the biggest water quality challenges facing environmental engineers, causing ecosystem health decline and requiring significant treatment before water is safe for human use. The remediation of nutrient pollution can occur along the river corridor where nutrients can be retained and transformed to environmentally benign products (e.g. N₂) by microbially mediated reactions. Catchment mismanagement, especially the removal of wood from channels, has reduced the capacity of rivers to fulfil this function, limiting reactions by two primary mechanisms: transport and reaction kinetics. These limitations could be abated by restoring rivers with instream wood, thereby providing a Nature-based Solution to this persistent water quality challenge.

Little research has directly investigated the potential of wood introductions to increase nutrient transformations in the river corridor. Here, we present results on two linked experiments which investigated the transport and reaction kinetics of nutrients at different scales.

The transport limitation refers to the total flux of water into the hyporheic zone, a hotspot of biogoechemistry in the river sediment, and its residence time therein. Instream wood causes an obstacle for river flow which could induce hyporheic exchange of suitable properties to allow favourable nutrient transformations. To investigate this, we installed wood features in a lowland stream in the UK and conducted a series of smart tracer injections to estimate (metabolically active) transient storage using a powerful before-after-control-intervention experimental design.

The reaction kinetic limitation refers especially to the availability and quality of organic matter, which could be improved by wood decomposition. An incubation experiment investigates the potential of instream wood as a source of organic matter and the effect of this on nutrient transformation rates and greenhouse gas production.

Preliminary analysis suggests that wood is effective at increasing nutrient transformations in both mechanisms. In the incubation experiment, nutrient transformation rates were higher in systems with wood compared to those without. In the field experiment, more metabolically active transient storage was observed in the sub-reach where restoration features had been installed. Our results provide evidence for the effectiveness of wood in river restoration and the efficacy of Nature-based Solutions for water quality challenges.

How to cite: Howard, B., Baker, I., Kettridge, N., Ullah, S., and Krause, S.: Restoring instream wood as a Nature-based Solution to nutrient pollution, IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-704, https://doi.org/10.5194/iahs2022-704, 2022.

For demographic, societal and climatic reasons, many countries have to manage changing agricultural territories and the evolution of these agricultural territories should accelerate by the global changes. In the Mediterranean area, traditional gravity-fed irrigation systems and associated channel networks are still widely used in agricultural territories. These systems affect landscapes and have had a lasting effect on the water cycle. Gravity-fed irrigation water contributes to the creation or maintenance of wetlands and contributes to the recharge of aquifers. A specific biodiversity is observed in irrigated areas and in areas crossed by irrigation canal networks. On the outskirts of urban centers, urbanization often extends over agricultural land, leading to an abandonment of gravity irrigation. In a climate change context, gravity irrigation may also disappear in favour of other more water-efficient irrigation techniques.

The current challenges therefore relate to:

- the identification of solutions to ensure the sustainability of channel networks and to mitigate the impact of the disappearance of gravity-fed irrigation perimeters.

- the implementation of these solutions by land planners.

We focused our work on a business area created within a sector where water from channels formerly used for gravity-fed irrigation is now used for watering green areas via a pressure network. This choice makes it possible to perpetuate the network of canals carrying water over the territory but some services initially provided by the irrigated perimeters such as the groundwater recharge or the reception of a specific biodiversity are no longer guaranteed there.

The atypical management of a stormwater retention basin, combining stormwater and irrigation water, has led to the creation of an artificial wetland that encourages the establishment of aquatic-dependent vertebrate animal species, including the unexpected presence of typical reed bed species. On the other hand, the invertebrate population remains sparse due to the rather irregular watering rate of the wetland.

Monitoring of water levels in this wetland shows that this basin leads to very large exchanges of water, both to groundwater and to the atmosphere, which can compensate for the flows disturbance induced by the abandonment of gravity irrigation.

How to cite: Cognard-Plancq, A.-L., Thiery, A., Gillon, M., Marc, V., Mexler, J., Moiroux, J., Babic, M., Soumille, H., and Simler, R.: Abandonment of gravity-fed irrigation: how to mitigate the impact on biodiversity and water cycle, IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-286, https://doi.org/10.5194/iahs2022-286, 2022.

Over the last decades, there has been much interest in natural flood management (NFM). However, there is still a lack of evidence on the effectiveness of NFM in general and particularly land and soil management based NFM in medium to large scale catchments. This study investigates the effects of soil and land management based NFM in the lowland Pang and Blackwater catchments in the UK. It uses the Soil and Water Assessment Tool (SWAT) to model the effects of broadscale land use and crop rotation scenarios on peak flows in selected catchments, while considering uncertainties. The broadscale land use scenarios consisted of the conversion of the catchments’ land to broadleaf woodland and cropland, respectively, except for water and urban areas. The results indicate that the NFM effects vary across the catchments and depend on landscapes characteristics. In addition, the blanket conversion to broadleaf woodland or cropland has a larger effect on small peak flows than on large floods such as those of January 9 and February 6, 2014. Afforestation leads to a reduction of 10 to 16% of the modelled 2014 winter flood events. In contrast, implementing crop rotation scenarios increases the peak flows, with the increase depending on the crops used and tillage practice. These findings suggest that via bespoke woodland planting and farming practices, combined with other measures that can reduce the amount of flow reaching the river channel or delay the timing of the peak flow (eg. leaky barriers), flood risks can be minimized. The results of this study provide information that can benefit future decision making on flood risk reduction in suitable catchments.

How to cite: Badjana, H. M., Verhoef, A., Cloke, H. L., Julich, S., Camargos, C., McGuire, P., and Clark, J. M.: Assessment of the effectiveness of natural flood management in medium scale lowland catchments, IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-215, https://doi.org/10.5194/iahs2022-215, 2022.

“Merjas” represent temporary wetlands in the Sebou-Delta in the northwest of Morocco. These temporary wetlands have been partially incorporated in a large-scale irrigation system, but this ecosystem still provides ecosystem services to the riparian population besides providing a habitat area for animal and plant species, contributing to flood control and other cultural ecosystem services. However, temporary wetlands and the services they provide are perceived differently by stakeholders. In particular, the opposition of viewing them as productive lands that need to be further developed through drainage and irrigation facilities or as buffer zones for flood protection generates conflicts of their use and creates an unknown future of them. Nature Based Solutions, as an emergent umbrella concept that is based on natural processes enhancing biodiversity and the provision of ecosystem services, provides an interesting lens to study the (conflicting) multiple ecosystem services in temporary wetlands.

The objective of this study is to analyze the hydrological dynamics of merjas on a spatio-temporal scale using remote sensing, and how existing and future irrigation development could affect the provision of ecosystem services.

Our work combines hydrological analysis using remote sensing with an analysis of ecosystem services, based on field surveys. The results of the study will be formalized in different management scenarios and then used for discussion in multi-actor workshops. Our multidisciplinary approach brings about the originality of the work in a low-informed context where access to data is difficult.

The use of NBS in the case of the Gharb plain could contribute to solving the problem of flooding and conserve its socio-environmental heritage. We developed a framework consisting of 3 steps: definition of the framework, identification of the challenge and co-creation of scenarios. For our case study, we highlight the ecosystem characteristics of the environment and the importance of the participatory approach for the success of NBS. This roadmap aims to provide the actors involved with an updated reflection on the developments that could be implemented for temporary wetlands in the Sebou-Delta and to develop an approach of interest to other wetlands elsewhere to preserve natural resources and taking into consideration the effects of climate change.

How to cite: Choukrani, H., Lacombe, G., Hammani, A., Taky, A., Belaud, G., and Kuper, M.: Nature-based solution to study multiple ecosystems services in temporary wetlands: the case of the Sebou Delta in Morocco, IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-667, https://doi.org/10.5194/iahs2022-667, 2022.

Enhanced weathering (EW) is one of the most promising technologies for sequestering atmospheric carbon. It consists on accelerating the chemical weathering fluxes naturally occurring in soils, by means of the addition of silicate minerals (i.e., forsterite), used as amendments, to the soil. If crushed into micrometer-sized particles, these minerals are characterized by high dissolution rates, that may be further improved under high soil water content and low pH conditions. Before actually applying EW technique at the global scale for carbon sequestration, an in-depth characterization of weathering and carbon sequestration rates, under different environmental conditions, is needed, also looking at correlated beneficial/detrimental effects. In this context, modeling approaches may play a pivotal role, since they allow to achieve this goal without affording costs required by laboratory and field experiments. The present study describes the application of a dynamic mass balance model connecting ecohydrological, biogeochemical and olivine dissolution dynamics. The model is composed of four connected components and is solved through an explicit system of eight mass balance total differential equations and an implicit one having 22 algebraic equations.

In this study, the model is applied to two sites in Italy (i.e., Sicily, in the south and the Padan plain, in the north) and two in the USA (i.e., California, in the south-west and Iowa, in the north-central area). The most common crops for the case studies, i.e., wheat for Sicily and California and corn for the Padan plain and Iowa are here considered, along with the most frequent soil types, namely the clay loam for Sicily and California and the silty clay loam for the Padan plain and Iowa. Maps of lithological composition of bedrocks and spatial distributions of soil pH have been also used to calibrate the background weathering flux, responsible of the H⁺ consume from all the minerals naturally present in the soil. Apart from deriving the most suitable locations, among those presented, providing the highest weathering and carbon sequestration rates, these simulations allow to assess the role of different climate, crop and soil types on EW dynamics, in perspective to find the combination that maximizes the CO₂ sequestration.

How to cite: Cipolla, G., Calabrese, S., Porporato, A., and Noto, L.: The effects of seasonal variability of precipitation and vegetation cycle on enhanced weathering for carbon sequestration, IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-414, https://doi.org/10.5194/iahs2022-414, 2022.

Introduction

Soil erosion, sediment loss, and catchment degradation are typical of the combined effects of sea level rise and climate change at the coastline and further inland. We describe an integrated, multidisciplinary, nature-based solutions (NBSs) approach to resolving some of the most pressing issues facing coastal communities affected by hydrological impacts due to increasing water levels and saline intrusion. Our blue and green infrastructure solutions are developed for coastal Africa and are equally applicable and scalable to coastlines and hydrological systems around the world where sediment starvation, changing rainfall patterns, and saline intrusion of the coastal aquifer are causing major changes to natural ecosystems, human habitats, and agriculture.

Methods

We use a systems approach that combines modeling and data collection to examine the complete system, from upstream riverine inputs and reservoirs to coastal wetlands, the littoral system, and the coastal aquifer. We emphasize the requirement to understand the interactions between existing natural and artificial assets as a precursor to recommending any management changes to the natural or anthropogenic infrastructure systems in place. A combination of NBSs and novel management techniques are proposed to restore natural sediment and freshwater supplies to coastal communities. We introduce two new green infrastructure types, which have been extensively tested and have the potential to significantly reduce erosion while simultaneously providing desalinated water (and electricity) to nearby coastal communities. We hypothesize that it is possible to reduce the extent of land degradation caused by saline intrusion through better management of water abstraction in the coastal aquifer.

Results

We expect our approach to deliver significant environmental and socio-economic co-benefits to coastal and inland communities and ecosystems, many of which are already suffering from the effects of land degradation and a lack of investment. When our NBSs are combined, their synergy greatly increases benefits on a regional scale.

How to cite: Friend, P., Amrouni, O., Ceberio, O., Dahmani, A., Diagne, B., Gaye, I., Jones, C., Koomans, R., and Staby, W.: Sea level rise and climate change hazards: an integrated and multidisciplinary NBS approach to the hydrological impacts of erosion and land degradation, IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-226, https://doi.org/10.5194/iahs2022-226, 2022.

In the coming century, people in low-lying coastal urban areas are projected to face an increase in coastal flood risk due to increases in, for example, urban development, sea-level rise, subsidence, and degradation of foreshore vegetation. To prevent this increase, or even to reduce risk below today’s levels, adaptation measures must be implemented. Nature-based adaptation in coastal areas, such as vegetation on the foreshore, is showing potential to mitigate the impacts of climate change. However, to our knowledge no studies have been carried out to assess and quantify the potential effectiveness of these nature-based or hybrid measures on a global-scale. Therefore, this study aims to provide a global scale assessment of nature-based (i.e. mangrove restoration and conservation of foreshore vegetation), structural (i.e. grey infrastructure) and hybrid (a combination of the latter two) adaptation measures to quantify its potential effectiveness. Although quantifying nature-based or hybrid adaptation can be challenging, it is critical to document such efforts to better understand their effectiveness. To achieve this, we develop a methodology to assess these adaptation measures in a global coastal flood risk modelling cascade. We will use this modelling framework to assess the benefits and costs of nature-based, structural and hybrid adaptation measures at the global scale. To address uncertainty of future conditions, we include a range of socioeconomic change projections and sea-level rise projections including uncertainties. The results of this study have major policy implications as it highlights the potential effectiveness of hybrid strategies at the global scale and shows where it is beneficial from an economic point of view to implement which strategies when assessing the direct benefits of the adaptation measure through flood risk reduction. This study will therefore be crucial to highlight regions where these adaptation measures might benefit for further research at the regional/local scale.

How to cite: Tiggeloven, T., de Moel, H., and Ward, P.: Towards nature-based and hybrid adaptation to coastal flood risk: a global perspective, IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-246, https://doi.org/10.5194/iahs2022-246, 2022.

The traditional means of urban water management relied heavily on engineering measures, or the use of “gray” infrastructure. Recently, there has been a call to integrate green infrastructure. This study conducts a systematic survey to characterize various nature-based solutions (NBS) adopted in different regions of the world and to elaborate on the benefits and limitations. It highlights the role of NBS in urban flood risk management under ongoing climate change and rapid urbanization. It shows that NBS could effectively mitigate urban flooding caused by high-frequency precipitation events, with additional economic, ecological, and social benefits. However, NBS are less effective at helping cope with pluvial flooding caused by extreme precipitation events over a short period of time, while gray infrastructures also have limitations as a mitigation measure against extreme pluvial flooding. It is thus recommended that integrating green and gray infrastructure is critical for urban water management, in particular with deep uncertainty in future.

How to cite: Liu, J.: Nature-based solutions for urban water management, IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-565, https://doi.org/10.5194/iahs2022-565, 2022.

The continuous urbanization growth, combined with climate changes, that are leading to more frequent intense rainfall events, is increasing the pluvial flood risk in urban areas. With the aim to mitigate urban floods, several blue-green solutions have been proposed in the literature. Among them, multilayer blue-green roofs have shown high potential, ensuring a high retention and storage capacity and providing many additional benefits to support a sustainable development of smart and resilient cities. Stored water can be reused for different domestic non-drinkable purposes, such as the irrigation of private gardens or cleaning the streets. Moreover, multilayer blue-green roofs facilitate the building thermal insulation, reducing the energy consumption, and help contrasting the urban heat islands. These nature-based solutions, however, have been mainly investigated only at building scale. In this work, we aim to evaluate the potential impacts of a large-scale installation of multilayer blue-green roofs over a large neighborhood or an entire city. Two multilayer blue-green roofs, installed in Cagliari and Perugia (Italy) as part of the EU Climate-KIC Polderroof field lab project, are used to calibrate an ecohydrological model to simulate the potential retention and storage capacities of these nature based solutions. The impact of a large-scale installation of multilayer blue-green roofs over the cities of Cagliari and Perugia is estimated, after having identified all the potential suitable roofs of these urban areas. The potential discharge reduction and water storage capacity are discussed also in a context of climate changes, simulating the impact of future climate scenarios, derived from the IPCC projections (RCP8.5), on the runoff mitigation capacity of multilayer blue-green roofs.

How to cite: Cristiano, E., Annis, A., Viola, F., Deidda, R., and Nardi, F.: Large-scale impacts of multilayer blue-green roofs: pluvial flood mitigation capacity and water storage capacity, IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-710, https://doi.org/10.5194/iahs2022-710, 2022.