Evaluation of flow regime in mediterranean streams using flashiness index

In the Mediterranean region, precipitation is characterised by a high spatial and temporal variability; this has a great influence on the flow regime and extreme flow events of a stream. Flow regime, in rum, has multiple impacts on erosion and sediment delivery, non-point source pollutant transport and biological communities inhabiting a stream. This paper presents a study aimed at analysing the flow change rates of a number of Mediterranean streams using the Richards-Baker (R-B) Flashiness Index, which measures streamflow variations in response to rainfall events. The flashiness is affected by some basin characteristics: climate, topography, land use, management, soil type, and other factors. The R-B Index values were then related to watershed size, location and baseflow discharge. They were compared to the Aridity Index of the area, and the daily flow variation coefficient. The authors report that the R-B Index values in the studied basins, generally, show an increase over time. The intermittent rivers studied present a considerable inter-annual variation of this index, together with mean annual values higher than the permanent rivers studied. In the southern Mediterranean area, the rivers assume higher values of R-B Index than those located in the northern area. Streams draining small watersheds show a very flashy character, indicating a very quick response to rainfall. These results suggest further investigation to analyse flood events.