Effectiveness of Nature-Based Solutions on Pluvial Flood Hazard Mitigation: The Case Study of the City of Eindhoven (The Netherlands)

Sandra Costa,Peter Roebeling,Rik Peters,Ricardo Martins,Jan Jacob Keizer,Luuk Postmes

doi:10.3390/resources10030024

Sandra Costa, Peter Roebeling + Show 4 more

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https://doi.org/10.3390/resources10030024

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Abstract

Urbanization leads to changes in the surface cover that alter the hydrological cycle of cities, particularly by increasing the impervious area and, thereby, reducing the interception, storage and infiltration capacity of rainwater. Nature-based solutions (NBS) can contribute to flood risk mitigation in urbanized areas by restoring hydrological functions. However, the effects of NBS on flood risk mitigation are complex and can differ substantially with the type of the NBS. Therefore, the effectiveness of NBS at the urban catchment scale is still subject to much debate, especially at the scale of urban catchments. In this study, the effects of different NBS on urban flood mitigation were evaluated for the city of Eindhoven in The Netherlands, as it has a history of urban flood events. To this end, various NBS scenarios were defined by municipal stakeholders and their impacts modelled with the numerical model Infoworks ICM. This was done for design storms with short, medium and long return periods (5, 10 and 100 years). Overall, the simulated NBS were effective in flood risk mitigation, reducing the flooded area as well as flood depth. The effectiveness of the individual NBS scenarios, however, depended strongly on the location and extension of the NBS, as well as on storm intensity. The effectiveness tended to increase with the increase in NBS surface area, while it tended to decrease with increasing storm intensity and, hence, return period. The NBS solution increasing street water storage was revealed to be more effective than those involving green car parks and green roofs. This study showed that numerical flooding models can be useful tools to assess the effects of NBS to reduce flood extent, water depth and/or velocity, providing insights that can support city planners to design and compare alternative strategies and plans for urban flood risk mitigation.

Highlights

Pluvial floods occur when surface runoff generation exceeds drainage capacity, often during high-intensity short-duration rainfall events [1,2]
Despite S5 presenting a larger implementation area, a higher decrease in the flooded area is expected for S6
For water storage scenarios, flood depth and velocity may increase in some neighborhoods

Summary

Introduction

Pluvial (or urban) floods occur when surface runoff generation exceeds drainage capacity, often during high-intensity short-duration rainfall events [1,2]. Increasing urbanization aggravates pluvial floods by expanding impervious surface areas and modifying flow paths. Future changes in land cover will increase the vulnerability of many urban areas to pluvial flooding due to extreme rainfall events [3]. Flood risk is defined as the probability that a flood event of a given magnitude and with a given loss will occur [5]. Flood risk involves two aspects: (i) flood hazard or the probability of occurrence and duration of flood events, which is determined by physical–environmental factors; (ii) flood vulnerability, which describes the elements that are exposed to the flooding event and their susceptibility to damages and losses [6,7,8]. Flood depth and flow velocity were selected in this study as key parameters to assess flood damage

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