GIS Water-Balance Approach to Support Surface Water Flood-Risk Management

Abstract

Controversy has arisen as to whether the lack of appropriate consideration to surface water flood risk in urban spatial planning is reducing the capacity to manage urban flood risk. A screening tool is required which would allow spatial planners to identify potential surface water flood risks and explore their management opportunities. An urban water balance approach is presented. The hypothesis is that key hydrological characteristics, storage volume and location, flow paths, and surface water generation, capture the key processes responsible for surface water flooding. The model is assembled and run by using ESRI ArcGIS software. Surface sinks and their catchment areas are identified by using a Lidar DEM. Excess surface water is calculated by using a runoff coefficient that is applied to rainfall volumes, and no other losses are considered. A surface water accumulation module sums the excess surface water from the catchment area of each sink. A sensitivity analysis of model assumptions demonstrates that these are valid for a screening tool. An informal validation of the model with local authority data revealed that most of the known flood risk locations were highlighted by the model. The model is applied to Keighley and sample results illustrate how knowledge of sink storage can be interpreted to explore opportunities for flood risk management. The model is a useful tool for quickly assessing potential flood risk locations and basic management options.