FLOODS AND SOIL EROSION
Water erosion is a part of the complex denudation of the earth’s surface. It is a phase in the weathering of rocks by running water, removing eroded material, and accumulating it in a new place. The basic feature of the erosion–transportation–accumulation process is the pronounced spatial and temporal organization in the hierarchy of hydrogeomorphologic systems. The trend toward the dynamic equilibrium between topography, soil, rocks, and hydraulic parameters of surface running water—selfregulation operating under natural laws—are characteristic features of such systems, ranging from a rill network on an elementary slope to the fluvial system of a large river basin. Running water works as a sculptor to transform the earth’s surface. Water-formed rills, trenches, gullies, ravines, valleys of small and large rivers, and peculiarly meandering networks of river channels, greatly change and often determine the structure of the earth’s landscapes. Rain and meltwater floods, while acting for a comparatively short time, much disturb the normal functioning of hydro-geomorphologic systems at any scale. This kind of erosion and the amount of transported loose material are greater by orders of magnitude than the erosion done by water flows at moderate or low flows. This is why the annual sediment load of most rivers predominantly occurs over a short period, such as two to three months, or even ten to twenty days. The high irregularity of run-off with time has an influence on the temporal variation of erosion intensity. This can be considered irregularly pulsative. It manifests itself in all temporal scales, ranging from an erosion event caused by a single rainstorm to seasonal, yearly, or geological timescales.
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