Abstract
Land use changes can significantly influence the water balance, and thus especially the development of flood-triggering runoff peaks. Hence, it is advisable to assess possible changes already at the level of municipal planning. Since many different actors are usually involved in spatial planning, it is useful to provide a shared platform where stakeholders can access the same information to analyze and evaluate flood hazards. Therefore, a GIS routine for the prediction of soil sealing induced runoff peaks and resulting potential flooding in the watercourse was developed, which is embedded in a GIS based decision support system (GIS-DSS). The so-called storm water routine (SWR) is founded on preprocessed flood characteristics, calculated by means of hydrological/hydraulic models (described in part 1). The potential impact of land use change is assessed purely in GIS as flow difference which is routed through the river system. To validate this simplified method, a process model was set up with an exemplary land use change and its results were compared with the GIS-based results. For 16 of the 18 rainfall scenarios tested, the SWR provided very good to good agreement with the detailed model. For short and highly dynamic rain events the SWR approach is less reliable. Several supplements like the integration of LID are conceivable.
Highlights
Since the beginning of human settlement history, humans have preferred to settle near rivers and streams
While part of this paper has described the set-up and parametrization of thecalcupromodel and the definition of rainfall scenarios, this article focuses on the geo-information system (GIS)-based cess model and the definition of rainfall scenarios, this article focuses on the GIS-based lation of additional runoff and the routing
Using the simulation results for the maximum surface runoff andsurface the maximum rainfall intensity, the peak runoff coefficients for the current state were calculated according fall intensity, the peak runoff coefficients for the current state were calculated according to Figure shows the correlation of the peak runoff coefficient and the degree to Equation (1)
Summary
Since the beginning of human settlement history, humans have preferred to settle near rivers and streams. Small settlements became large settlements and these became today’s cities. Areas formerly close to nature are rezoned as building land and cities are redensified. This inevitably leads to increased soil sealing. Soil sealing strongly modifies the water cycle by reducing infiltration, evapotranspiration, and groundwater recharge, intensifying (rapid) surface runoff. The risk of flooding is increased [1,2] especially where no retention areas exist. For a region in China it has been shown that over the last 20 years urbanisation has led to an increase in the runoff coefficient of 13.4%, resulting in an increase in the maximum flood discharge of 12.9%
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