What controls the width function shape, and can it be used for channel network comparison and regionalization?
Résumé
The width function captures the essential features of the catchment's GIUH's response. This paper aims to identify the morphometric properties which control the shape of the width function, and assess whether these properties can be used as similarity indices for catchment comparison. A new deterministic iterative model of the width function is proposed on the basis of a conceptualization of the topology of the channel network, and exploiting the morphometric characteristics of internal and external nodes. Tests are carried out on eleven French catchments and compared to the reference Peano catchment. Results show that the morphometric properties of three main internal and external nodes such as the drained area, the distance to the outlet, and the position on the channel network are useful descriptors for modeling the width function and for representing the scaling properties of a channel network. While the GIUHs based on Horton- Strahler ratios are strongly related to the method used to extract the channel network from the DEM, the new indices are independent of the method used. They are sufficient descriptors to reproduce the main shape of the width function, the peak, the time to peak, and the main properties such as non- negativity, non- stationarity, and power law decay of the spectrum. They may be used to establish catchment typology,to compare catchments, and to classify the width function peaks for catchment regionalization