Deep excavation caused by water is called undermining. One of the types of water erosion can be due to the impact of waves against a cliff, to the eddies of water, especially where the current encounters an obstacle, and to friction with the banks of the currents that have been diverted by the sinuous beds. In the latter case it is faster in the first phase of the avenues "Avenue (hydrology)"). The undercutting causes the retreat of the waterfalls and cliffs which, being deprived of support at their base, progressively collapse. It also plays an essential role in the formation and migration of meanders.

Contenido

Se pueden distinguir dos tipos de socavación:.

General Undermining

General erosion is a long-term phenomenon, which we could call natural, it occurs in the upper part of the hydrographic basins, where the slope "Slope (geography)") of the talweg "Vaguada (geomorphology)") is high. As a consequence, the speed of the water and the drag capacity of the current is high. As the flow drags more material, the flow quickly reaches its potential drag capacity, which is a function of speed. At that point it no longer produces scour, the section, margins and bottom are stable. As you advance along the course of the river or stream, the slope decreases, consequently the speed decreases, and the current deposits the material it was transporting.

Localized undermining

The most typical cases of localized scour are:

This is a type of scour that consists of the excavation of material found around the pillars of a bridge, which can lead (if applicable) to the collapse of the structure. Among the best-known formulas for predicting scour depth around pillars founded on sandy beds are those of HEC-18 (FHWA Hydraulic Engineering Circular and FDOT (Florida Department of Transportation), through data analysis it has been observed that each of these formulas have a certain range of application; that is, ranges where the value of the predicted scour is closer to the calculated one.[1]​.

In a statistic carried out in 1976, on the causes of failure or breakage of 143 bridges around the world, it turned out:

This shows that hydraulic aspects are fundamental in bridges; A good knowledge of these aspects will make the bridge safer and cheaper.[2]​.