On the stormflow response of upland Alpine catchments.
Orlandini S., Perotti A., Sfondrini G., Bianchi A.


Abstract: Detailed measurements of near-surface soil hydraulic conductivity Ks across the Bracciasco catchment (Central Italian Alps) are incorporated into a distributed, digital elevation model--based hydrologic model to evaluate the impact of soil heterogeneity on catchment stormflow response. Surface and subsurface stormflow components are simulated for different distributions of Ks, including that obtained directly from measurements, that obtained by averaging measured data, and others obtained on the basis of a simple functional parameter model. The reproduction of the catchment stormflow responses obtained using distributions of Ks based on measurements is satisfactory although an adjustment of such distributions is suggested to reproduce the hydrograph peaks due to rapid surface runoff concentration and to improve the description of recession limbs at the same time. Numerical experiments indicate that the simulated stormflow response of the study catchment is substantially insensitive to near-surface soil heterogeneity as far as the predominant mechanism of channel stormflow generation is subsurface flow. However, Ks is found to play an important role in the land surface partitioning of intense rainfall peaks and, under these circumstances, monitoring of near-surface heterogeneity may be important to provide accurate descriptions of both surface and subsurface stormflow components.