Las avenidas torrenciales en cauces efímerosramblas y abanicos aluviales

Abstract

The torrential stream dynamics is characterized by ephemeral but sudden streamflows (flashfloods) that quickly reach their peak flow, entraining abundant load that also deposits abruptly when the flood vanishes. They offer wide range morphologies, from metric forms (gullies) on headwaters and slopes, to kilometric ones like ramblas (arroyos) and large alluvial fans. But their morphology and dynamics are similar: very active reception basin, short transference channel and widespread production area, commonly an alluvial fan. These three zones may be recurring at different scales within the same drainage line, generating deposits on which the channel either entrenches or abandons, migrating towards more depressed areas. This erratic and changing dynamics, the erosive capacity, as well as the high load and discharge, confer to these systems a great hazard.