High flow events and sediment transport in small streams in the ‘tertiary basin’ area in piedmont (Northwest Italy)

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Abstract
Rainfall, peak discharges, and suspended sediment transport were surveyed for 280 events in three small (0.8 to 10 km2) catchments in a hilly area derived from Neogene marls, silts, and sands.Under similar hydrological input conditions, stream flow behaviour and sediment delivery differed considerably from one catchment to another, depending on topography, lithology, land use, and especially sediment availability. Analytical treatment of data showed a good fit between sediment yield and peak flow discharge. Less good, although still significant, was the correlation between sediment concentration and discharge values for different flow stages. Rainfall peak/basin lag time and rainfall/discharge showed poor or no correlation, mainly due to strong variations in rainfall distribution.Sediment concentration in the catchments varied enormously according to season, from zero up to 334 g 1−1; sediment yield was 160‐900 tonnes km−2 yr−1 in the two major catchments, and over 5200 tonnes km−2 yr−1 in the headwater catchment, stressing the importance of small tributaries not only in inducing floods in downstream channels, but also in sediment supply.