Impact of grid size in GIS based flood extent mapping using a 1D flow model

Flood hazard in areas adjacent to rivers may be estimated by applying hydrological/hydraulic models to calculate parameters such as flood extent, depth and duration. Using a two-dimensional flow model based on the topography has the drawback that computational requirements are high, making this approach unattractive when applying in, for example, a decision support system. This paper presents a simple GIS based method for assessing the extent and depth of flooding based on water levels calculated using a I-dimensional flow model and an extended inverse distance interpolation method. Local depressions not directly connected to the river by a continuous water surface are easily removed. The method is demonstrated on a 9 km(2) floodplain area, where the effect of varying grid size on flood extent estimation and evaluation time is investigated. Possible points of improvement as well as future work to assess the accuracy are discussed. (C) 2000 Elsevier Science Ltd. All rights reserved.