engleski

Sediment transport in relation of forest cover progression in a small scale Mediterranean catchment

Decrease of sediment transport is one of the major indicators of forest ecosystem stability. Forests have highly performing regulatory functions on the water cycle among others especially in Mediterranean environments characterized by high temporal contrasts in weather conditions. Sediment transport is a specific form of soil particles movement in the catchments which takes place due to complex interaction processes between topographic, hydrological and geological characteristics, climate, soil, vegetation cover, and human activities. The aim of this study was to assess the effect of forest vegetation in decrease of sediment transport – soil loss. To improve that statement, experiment was conducted in small Mediterranean catchment, Suvava (Central Dalmatia, Croatia). The catchment covers area of 1823 ha, with the length of the main stream of 10.1 km and the entire length of greater and smaller tributary streams of 20.8 km. Altitude is between 460 and 961 m above the sea level. The soil is classified as marl limestone, shallow and very skeletal. The climate is sub-Mediterranean, average annual precipitation is 1200 mm and average annual temperature is 13°C. The rainy season takes place from October to April, though summers are hot and very dry. The main land uses are: forestry 60 % (pine and oak), followed by shrub area 20%, agricultural areas 15 % and bare area 5%. Monitoring began in Suvava catchment in 1972 and lasted until 1975. In 2009 monitoring was re-established. The equipment in the catchment provided information about meteorological variables, water level and water flow (discharge). For each event, rainfall and runoff volumes, runoff coefficient, and peak flow were determined. All these variables, as well as sediment transport, were analysed to characterize the hydrological functioning of the catchment. The results obtained were compared to those from the previous period (1972-1975) when the catchment was under human disturbance, cultivated and grazed. In above mentioned period, the catchment was covered by pine and oak forest (20 %), shrub (5%), agricultural land 15 % and bare land 55 %. The obtained results demonstrated that sediment transport is significantly lower nowadays when 60 % of the catchment area is covered by forest compared with the period from the 1972 to 1975 when only 20 % was covered by forest. Annual runoff coefficients are low and do not exceed 10 % in both periods. Forest cover in the catchment significantly reduced sediment transport.

sediment transport, catchment, forest progression, flow off

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