The influence of riverine wetlands on flood and drought mitigation::a case study for the Aa, the Netherlands

Due to a changing climate, there will be more<br/>extreme weather, influencing the discharge in river<br/>systems. Large discharges can cause flooding,<br/>while small discharges, due to longer dry periods,<br/>can cause droughts (IPCC, 2023). Proper water<br/>management in rivers, like the implementation of<br/>Nature based Solutions (NbS) can reduce the<br/>impacts of these natural hazards while at the same<br/>time providing environmental, economic, and<br/>social benefits (Nelson et al., 2020). There is a<br/>wide range of NbS possibilities, with riverine<br/>wetland creation or restoration being one of them.<br/>Riverine wetlands have been proven to be<br/>effective in reducing flood risks and droughts<br/>(IPCC, 2023; Y. Wu et al., 2023), however there is<br/>still a lot unknown on the functioning of these NbS<br/>regarding flood as well as drought reduction as<br/>there are many factors, like for example size,<br/>location and vegetation that influence the<br/>functioning of wetlands (Mohamed et al., 2012;<br/>Ogawa &amp; Male, 1990; Tang et al., 2020).<br/>Therefore, it is necessary to look further into the<br/>hydrological functioning of wetlands.<br/>The objective of this research is to investigate if a<br/>wetland is a suitable solution for flood and drought<br/>reduction in the Aa catchment, the Netherlands<br/>and to provide a recommendation on how to adapt<br/>for climate change based on the results of this<br/>thesis. In this “suitable solution” can be defined as<br/>a solution providing flood and drought mitigation<br/>for the Aa river for the current and future climate<br/>taking climate change into consideration.<br/>To reach this aim four research questions were set<br/>up:<br/>1. What riverine wetland type(s) can be<br/>implemented best in the Aa and how to model<br/>these wetland types in SWAT+?<br/>2. How can suitable locations for wetland<br/>creation or restoration in the Aa be defined?<br/>3. What is the influence of riverine wetlands on<br/>flood mitigation in the Aa in the current and<br/>future climate?<br/>4. What is the influence of riverine wetlands on<br/>drought mitigatio