Incised or Entrenched Meanders
In streams that flow rapidly over steep gradients, normally erosion is concentrated on the bottom of the stream channel. Also, in the case of steep gradient streams, lateral erosion on the sides of the valleys is not much when compared to the streams flowing on low and gentle slopes. Because of active lateral erosion, streams flowing over gentle slopes develop sinuous or meandering courses. It is common to find meandering courses over floodplains and delta plains where stream gradients are very gentle. But very deep and wide meanders can also be found cut in hard rocks. Such meanders are called incised or entrenched meanders (Figure).
Incised meanders are meanders which are particularly well developed and occur when a river’s base level has fallen giving the river a large amount of vertical erosion power, allowing it to downcut. There are two types of incised meanders, entrenched meanders, and ingrown meanders. entrenched meanders are symmetrical and form when the river downcuts particularly quickly. Meander loops develop over original gentle surfaces in the initial stages of development of streams and the same loops get entrenched into the rocks normally due to erosion or slow, continued uplift of the land over which they start. They widen and deepen over time and can be found as deep gorges and canyons in hard rock areas. They give an indication of the status of original land surfaces over which streams have developed.