Effects of different methods for estimating impervious surface cover on runoff estimation at catchment level

Frank Canters 1, Jarek Chormanski 2, Tim Van de Voorde 1 and Okke Batelaan 2
1 Department of Geography, Vrije Universiteit Brussel
Pleinlaan 2, B-1050 Brussel, Belgium
Tel.: + 0032 2 629 3381; Fax: + 0032 2 6293378
fcanters@vub.ac.be, tvdvoord@vub.ac.be
2 Department of Hydrology and Hydraulic Engineering, Vrije Universiteit Brussel
Pleinlaan 2, B-1050 Brussel, Belgium
Tel.: + 0032 2 629 3039; Fax: + 0032 2 6293022
jchorman@vub.ac.be, batelaan@vub.ac.be

Abstract
One of the most obvious effects of urbanization is an increase  of impervious surface cover. Surface imperviousness has an important impact on hydrology, stream water quality and ecology, and is often used as an overall indicator of the health status of urbanized watersheds. It has also been identified as one of the key  factors in the occurrence of flash floods. This paper examines the impact of different methods for estimating impervious surface cover on the outcome of a distributed rainfall-runoff model for the upper catchment of the Woluwe River in the southeastern part of Brussels. The study shows that mapping of impervious surface distribution, using remotely  sensed data, produces substantially different estimates of discharge at catchment level than traditional approaches that are based on expert judgment of average imperviousness for different types of urban land use.  Little difference is observed between results obtained with detailed impervious surface maps derived from high resolution satellite data and sub-pixel estimates of imperviousness derived from medium resolution data. This demonstrates that sub-pixel classification may be an interesting alternative for more expensive high resolution mapping of imperviousness for rainfall-runoff modeling at catchment level.

Keywords: impervious surfaces, runoff modeling, remote sensing, sub-pixel classification

In: Caetano, M. and Painho, M. (eds). Proceedings of the 7th International Symposium on Spatial Accuracy Assessment in Natural Resources and Environmental Sciences, 5 – 7 July 2006, Lisboa, Instituto Geográfico Português

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