The role of land use–land cover on runoff generation and sediment yield at a microplot scale, in a small Mediterranean catchment

Abstract

Replied runoff–erosion microplots (less than 1 m 2) have been set up in eleven environments representative of the land uses in the catchment, in order to measure and evaluate their rates after each rainfall event, during dry and wet soil conditions (summer and winter, respectively). Recorded rainfall amounts and intensities were higher in summer (47 l/m 2 and 0.82 mm/h, respectively) than in winter (38.25 l/m 2 and 0.45 mm/h, respectively). Thus, runoff and sediment yield rates were greater in summer than in winter in all the environments. The highest runoff and erosion values, ranging from 0.84 to 13.49 l/m 2 and from 11.26 to 648.43 g/m 2, respectively, were measured under the cultivated olive trees environment during dry soil conditions. According to the literature data, these values may be considered very low. Cork tree environments presented the lowest values of runoff and sediment yield over the study period, presumably accounting for the importance of the vegetation cover in terms of soil protection as well as its role in improving the soil physical and chemical properties. Slightly higher significant correlation ( p<0.05) between runoff and soil loss was found in winter (+0.38) than in summer (+0.30), analysing all the rainfall events and environments. Negative relationship ( p<0.05) between vegetation cover and soil loss (−0.40) and runoff (−0.31), was only found in winter. Strong correlation between runoff and precipitation was revealed in both study seasons (+0.57 summer and +0.34 winter). Analysis of variance (ANOVA) indicates significant differences in sediment yield between the selected environments as well as the land use–land cover in winter. The high variation in the total runoff and sediment loss measured in the different environments reflects the great importance of total rainfall as well as land use on these variables. It was found that land use/cover, farmland set-aside and land misuse, can greatly affect runoff and soil erosion.