Peak flow estimations in Montesinho Natural Park applying the SCS method
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Lameiros, grasslands typical of Northern Portugal, have high environmental and landscape value, also contributing to ecosystems services provision in mountain areas. Their position in the headwaters of large basins contributes to the regulation of hydrological risks, stressing their importance in the context of global change. In Montesinho Natural Park (PNM), a Protected Area in Northeast Portugal, lameiros face land abandonment, as located in areas with sharp demographic decline.
In this work, we estimated peak flow and analysed the influence of Lameiros on the hydrological responses of small catchments in PNM applying the Soil Conservation Service (SCS) method. Sixteen catchments were selected, including managed and abandoned lameiros. We estimated peak flow in the current condition and in that simulating scenarios of decreasing precipitation amounts that consequently increase rainfall intensities, eventually with impact on the occurrence of hydrological risks. For applying the SCS method, data on catchments characteristics was used, such as topography, soil type and land use. Catchments studied were grouped as follows (4 each group): 1) with manged lameiros and with permanent stream; 2) with abandoned lameiros and with permanent stream; 3) with manged lameiros and with no permanent stream; 4) with abandoned lameiros and with no permanent stream.
Future climate simulation scenarios considered an increase of 21 and 32% in rainfall intensities until 2100, based on the Municipal Strategy of Adaptation to Climate Change (EMAAC ). Results obtained show differences in peak flow between catchments with permanent stream (with the highest values) and without permanent stream. The areal proportion of lameiros in the catchment partially affects its response to intense rainfalls. Simulation considering future climate scenarios outcome an increase of 54% (21% increment until 2070) and 86% (by the 34% increment until the year 2100) in peak flow, when compared with the present situation. In these scenarios, it was observed that peak flow is higher in catchments with no permanent stream and in those with abandoned lameiros.
