Kowit Boonrawd and Chatchai Jothityangkoon

pp. 171 - 181

Abstract

A coupling of a 1-D flood routing model and quasi 2-D floodplain inundation model is applied for mapping spacetime flood extent. The routing model is formulated based on a non-linear storage-discharge relationship which is converted
from an observed and synthetic rating curve. To draw the rating curve, required parameters for each reaches are estimated
from hydraulic properties, floodplain geometry and vegetation and building cover of compound channels. The shape of the
floodplain is defined by using fitting exercise based on the reverse approach between past and simulated inundation flood
extent, to solve the current problem of inadequate topographic input data for floodplain. Mapping of daily flood can be
generated relying on flat water levels. The quasi 2-D raster model is tested and applied to generate more realistic water surface
and is used to estimate flood extent. The model is applied to the floodplains of Chiang Mai, north of Thailand and used to
estimate a time series of hourly flood maps. Extending from daily to hourly flood extent, mapping development provides more
details of flood inundation extent and depth.