Abstract:
In flood hydrology, geomorphological catchment characteristics serve as fundamental input
to inform decisions related to design flood estimation and regionalization. Typically, site-specific
geomorphological catchment characteristics are used for regionalization, while flood statistics are
used to test the homogeneity of the identified regions. This paper presents the application and
comparison of Geographical Information Systems (GIS) modelling tools for the estimation of catchment
characteristics to provide an enhanced understanding of the linkage between geomorphological
catchment characteristics and response time. It was evident that catchment response variability is
not exclusively related to catchment area, but rather associated with the increasing spatial–temporal
heterogeneity of other catchment characteristics as the catchment scale increases. In general, catchment
and channel geomorphology overruled the impact that catchment variables might have on the response
time and resulting runo . Shorter response times and higher peak flows were evident in similar-sized
catchments characterized by lower shape factors, circularity ratios, and shorter centroid distances
and associated higher elongation ratios, drainage densities and steeper slopes. The GIS applications
not only enabled the inclusion of a more diverse selection of catchment characteristics as opposed to
when manual methods are used, but the high degree of association between the di erent GIS-based
methods also confirmed their preferential use.
