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De Waterbergende Weg: Lokale effecten hydrologie (WP2)

International knowledge exchange on infiltration of stormwater under extreme climate and geohydrolic circumstances

Urbanisation and climate change have an effect on the water balance in our cities resulting in challenges as flooding, droughts and heatstress. Implementation of Sustainable Urban Drainage Systems (SuDS) can help to restore the water balance in cities by storing and infiltrating stormwater into the subsurface to minimise flooding, restoration of groundwater tables to prevent droughts, lowering temperatures by evapotranspiration to fight heatstress. Urban planners and otherstakeholders in municipalities and water authorities struggle with implementing SuDS at locations where infiltration of water seems challenging. Questions arise as: can you infiltrate in countries as The Netherlands with parts under sea level, high groundwater table and low permeable soil? Can you infiltrate in Norway with low permeable or impermeable bedrock and frozen ground most of theyear? How do you find space to implement SuDS in the dense urban areas of Bucharest? These questions are answered by researchers of the JPI Water funded project INovations for eXtreme Climatic Events (INXCES).To answer the question on ‘can we infiltrate stormwater under worse case conditions?’, testing of the hydraulic capacity take place at rainwater gardens in Norway (Bergen and Trondheim) and (bio)swales in the low lying parts of The Netherlands. The first results show that even under these ‘extreme’ hydraulic circumstances the hydraulic capacity (or empty time) is sufficient to infiltratemost of the stormwater throughout the year.INXCES exchanged researchers on an international level, shared research results with stakeholders and sets up guidelines for design, implementation and maintenance of SuDS to promote the implementation of sustainable water management systems throughout the world.One of the tools used to promote SuDS is www.climatescan.nl, an open source online map application that provides an easy-to-access database of international project information in the field of urban resilience and climate adaptation. The tool is able to map several sustainable urban drainage systems as has been done for Norway, The Netherlands, Romania and other countries in the world.The tool is used for engagement with stakeholders within EU projects as INXCES and WaterCoG and resulted in international knowledge exchange on infiltration of stormwater under extreme climate and geohydrolic circumstances.

XRF quick-scan mapping for heavy metal pollutants in SuDS: a methodological approach

Sustainable urban drainage systems (SuDS) such as swales are designed to collect, store and infiltrate a large amount of surface runoff water during heavy rainfall. Stormwater is known to transport pollutants, such as particle-bound heavy metals, which are known to often accumulate in the topsoil. In this study, a portable XRF instrument is used to provide in situ spatial characterization of soil pollutants. The method uses portable XRF measurements of heavy metals along profiles with set intervals (1 meter) to cover the swale with cross-sections, across the inlet, the deepest point and the outlet. Soil samples are collected, and the In-Situ measurements are verified by the results from laboratory analyses. Stormwater is here shown to be the transporting media for the pollutants, so it is of importance to investigate areas most prone to flooding and infiltration. This quick scan method is time and cost-efficient, easy to execute and the results are comparable to any known (inter)national threshold criteria for polluted soils. The results are of great importance for all stakeholders in cities that are involved in climate adaptation and implementing green infrastructure in urban areas. However, too little is still known about the long-term functioning of the soil-based SuDS facilities.

Risk assessment for urban areas prone to flooding and subsidence

One of the goals for the JPI Water funded project INovations for eXtreme Climatic Events (INXCES) is to provide risk assessment tools for urban hydro-climatic events. Combining disciplines increases the capacity to manage and improve the mitigation of the infrastructure for stormwater in urban areas. INXCES is an European collaboration among the cites Bergen, NO, Groningen, NL, Bucharest, RO, and Luleå, SE.In urban areas infrastructure, such as sewage and drainage systems, is installed in the subsurface to cope with surface water and stormwater runoff. However, the natural patterns are preferred hence human effort. A flood model using Digital Elevation Model (DEM) show the flow patterns of stormwater and areas exposed to flooding. Combining mapping of natural flow paths and floodmodelling, areas prone to flooding is accentuated. The subsurface infrastructure in these prone areas are exposed to larger quantities of water during heavy rainfall events, which is becoming more frequent due to climate change. Results from this interdisciplinary study, will give the water and wastewater authority a risk assessment to pinpoint areas where water infrastructure is more exposedto failure, clogging and damages. Furthermore, we argue that areas that are prone to repeated flooding are more exposed for subsidence in the ground. Larger movement in the ground will cause damage to the infrastructure, such ascracking of pipelines and damage to buildings, roads etc. By combining results mentioned above with subsidence data (InSAR date collected from Satellites), a risk assessment map can show areas to prioritize. Subsurface measures such as SUDS (Sustainable Urban Drainage Systems) can be a resilient solution to a recurrent problem in an urban area, as a remediation to flooding (and drought)and as stabilisation of ground conditions.

In situ mapping of pollutants in Sustainable Urban Drainage Systems, a new methodology approach and preliminary results from the Netherlands

In situ mapping of pollutants in Sustainable Urban Drainage Systems, a new methodology approach and preliminary results from the Netherlands

Stormwater runoff has severe negative and direct impact on the quality of surface waters and groundwater. The impact can cause chemical and heavy-metal pollution. Applying well established methods to map pollutants in urban areas and specifically in Nature-Based Solutions (NBS), such as Sustainable UrbanDrainage Systems (SuDS) is a step towards improving the water quality in the urban water cycle. Traditional mapping of pollutants by the means of soil samples is costly, which is the main reason why the environmental-technical functioning of rainwater facilities has not been investigated on a large scale andsystematically. X-ray fluorescence (XRF) is a known analysing method for finding metals and other components, for laboratory analysis and portable instruments. In this work we propose a new approach of mapping method for pollutants in-situ, such as heavy metals in soil in SuDS, with case studies from theNetherlands where swales were implemented 20 years ago. In situ XRF measurements is a quick and costefficient analysis for heavy meatal mapping in the respect to contaminated soil. In situ XRF measures of various elements, including heavy metals is carried out in a quickscan and accurate manner and measures both qualitatively and quantitatively. It makes the time-consuming and costly interim analyses by laboratories superfluous. In this study, we suggest a new methodology approach for in situ mapping of pollutants in various swales that were implemented from 20 to 5 years ago. The results differ due to multiple factors (age, use of materials, storage volume, maintenance, run off quality, etc.). Several locations reached unacceptable levels, above the national thresholds for pollutants. The spatial distribution of pollutants in the over 30 swales mapped in the Netherlands show that the preferred water flow in theSuDS controls the spreading of pollutants. The swales investigated are presented in an interactive way with the open source tool www.climatescan.nl, containing more than 100 swales, part of which has been investigated with in situ XRF measurements. The research results are of great importance for all stakeholders in (inter)national cities that are involved in climate adaptation. SuDS is the most widely used method for storing stormwater and infiltrating in the Netherlands. However, there is still too little knowledge about the long-term functioning of the soil of these facilities.