Scales and similarities in runoff processes with respect to geomorphometry

Numerous investigations using various techniques have been carried out towards a more detailed understanding of relationships and interactions between morphometry and rainfall runo} processes[ Recently this research question has become more relevant through the need for accurate yet simple computer models simulating the water balance of large areas[ Moreover advances in the analysis of landform morphometry through the availability of high!resolution digital elevation models DEMs# and powerful geographical infor! mation systems GIS# have enhanced research e}orts with this aim[ In this study several computer techniques and models were applied to investigate the e}ects of geo! morphometry on rainfall runo} at di}erent scales[ The sensitivity of dynamic hydrological to comparatively static boundary conditions requires di}erent methods for analysis and visualization of di}erent kinds of data appropriate to di}erent scales[ an approach integrating several geo! computational concepts spatial analysis of di}erent types of geodata static modelling of spatial structures dynamic four!dimensional modelling of hydrological and statistical techniques was chosen[ Geomorphometric analysis of the study sites was carried out with GIS packages including ARC:INFO and GRASS# special purpose software and self!developed tools[ Soil morphometry relationships were modelled within a GIS environment[ Hydrological models SAKE and TOPMODEL# were then used to simulate rainfall runo} processes and _nally statistical tools and sensitivity analysis were applied to gain an insight into the hydrological signi_cance of the various geomorphometric properties[ The results demonstrate the importance of small subregions of the catchment particularly those having low slope angles low ~ow lengths and concavities[ The spatial distribution of soil types signi_cantly in~uences modelled runo}[ Spatial distributions of soil types are partly related to morphometry and can be captured using soil morphometry models[ Further results show that catchments which di}er signi_cantly in mor! phometry show di}erent runo} responses and di}erent hydrological sensitivity to changes in boundary conditions[ A crude derivation of geomorphometric hydrological landform types could be reached[ Therefore geomorphometric classi_cations of types could form a basis for representative hydrological mod! elling at the large scale[ Models describing soil distribution in relation to geomorphometry could assist regionalization of spatial heterogeneity and of soil parameters relevant in hydrological modelling[ Moreover quanti_cation of geomorphometric structure e[g[ in terms of contributing areas is needed to describe signi_cant geomorphometric characteristics[ Copyright 1999 John Wiley + Sons Ltd[