The effects of the spatial variability of soil infiltration capacity in distributed flood modelling

Spatial variability is recognized to exert a remarkable influence on the catchment hydrological response over a wide range of scales. Accordingly, one of the main advantages of distributed rainfall-runoff models is their capability of accounting For its effects, The application of these models. however, is often limited by the large amount of data required. Particularly, the spatial characterization of both the vegetation cover and soil type is needed in order to describe properly the spatial distribution of the soil infiltration properties. Lack of these data. which are often quite difficult to obtain in practice, is one of the reasons which may induce hydrologists to prefer the application of lumped models, despite their lower capability of describing hydrological processes. A possible way out for preserving the distributed nat are of the model is neglecting the spatial variability of the soil infiltration process by lumping the correspondent model parameters at the basin scale, and describing the transfer of runoff production at the basin outlet through a distributed approach. Lumping the infiltration parameters might be a reasonable assumption if one is interested in modelling those situations where the spatial variability of the infiltration process is expected to exert a marginal effect on the river discharge. Accordingly, the present analysis is aimed at verifying the effects of the spatial variability of the soil infiltration parameters on the flood flows modelled by a distributed model, with special reference to a case study of a river basin located in northern Italy. The main purpose of this work is to derive indications in order to possibly reduce the data requirements of distributed models, thus encouraging their application even in the case of limited data availability. Copyright (C) 2000 John Wiley & Sons, Ltd.