Abstract
River managers of alluvial rivers often need to reconcile conflicting objectives, but stakeholder processes are prone to subjectivity, time consuming and therefore limited in scope. Here we present RiverScape, a modeling tool for numerical creation, positioning and implementation of seven common flood hazard reduction measures at any intensity in a 2D hydrodynamic model for a river with embanked floodplains. It evaluates the measures for (1) hydrodynamic effects with the 2D flow model Delft3D Flexible Mesh, and (2) the required landscaping work expressed as the displaced volume of material. The most effective flood hazard reduction in terms of transported material is vegetation roughness smoothing, followed by main embankment raising, groyne lowering, minor embankment lowering, side channel construction, floodplain lowering and relocating the main embankment. Implementation of this tool may speed up decision making considerably. Applications elsewhere could weigh in adverse downstream effects, degradation of the ecology and overly expensive choices.
Highlights
Flood risk reduction ranked high on the political agenda over the last two decades, which is warranted given the high and increasing societal cost of flooding, the anticipated ongoing climate change, and economic developments in fluvial and deltaic areas (Hirabayashi et al, 2013)
This is because the propagation of a flood wave, or flood wave celerity, increases with the flow velocity of the water and with the fraction of the discharge conveyed by the main channel (Jansen et al, 1979)
We aimed at the evaluation of flood stage reduction effects of seven landscaping measures with increasing intensity and its relation to displaced material
Summary
Flood risk reduction ranked high on the political agenda over the last two decades, which is warranted given the high and increasing societal cost of flooding, the anticipated ongoing climate change, and economic developments in fluvial and deltaic areas (Hirabayashi et al, 2013). Flood hazard management at the river basin scale consists of storing water in the headwater of the basin, retaining water instream in the middle parts and discharging the water in the downstream reaches (Hooijer et al, 2004). This is because the propagation of a flood wave, or flood wave celerity, increases with the flow velocity of the water and with the fraction of the discharge conveyed by the main channel (Jansen et al, 1979). We develop and apply the tool to a specific case of a lowland deltaic floodplain at the downstream end of the river Rhine, which is a medium-sized river draining part of North-West Europe
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