Answer: Running water is considered one of the most important geomorphic agents bringing about the degradation of the land surface. There are two components of running water. One is overland flow on the general land surface as a sheet and another is linear flow as streams and rivers in valleys. Significance of running water in the evolution of landforms:

• Most of the erosional landforms made by running water are associated with vigorous and youthful rivers flowing over steep gradients.
• With time, stream channels over steep gradients turn gentler due to continued erosion, and as a consequence, lose their velocity, facilitating active deposition.
• There may be depositional forms associated with streams flowing over steep slopes. But these phenomena will be on a small scale compared to those associated with rivers flowing over medium to gentle slopes.
• The gentler the river channels in gradient or slope, the greater the deposition. When the stream beds turn gentler due to continued erosion, downward cutting becomes less dominant lateral erosion of banks increases and as a consequence, the hills and valleys are reduced to plains.
• Overland flow causes sheet erosion. Depending upon irregularities of the land surface, the overland flow may concentrate into narrow to wide paths forming rills, gullies, and ultimately valleys.

Depositional Features of Running Water

Feature	Characteristics	Diagram
Alluvial Fans	Alluvial fans are formed when streams flowing from higher levels break into foot slope plains of low gradient. Normally very coarse load is carried by streams flowing over mountain slopes. This load becomes too heavy for the streams to be carried over gentler gradients and gets dumped and spread as a broad low to high cone-shaped deposit called an alluvial fan.
Deltas	Deltas are like alluvial fans but develop at a different location. The load carried by the rivers is dumped and spread into the sea. If this load is not carried away far into the sea or distributed along the coast, it spreads and accumulates as a low cone. Unlike in alluvial fans, the deposits making up deltas are well very sorted with clear stratification.
Floodplains, Natural Levees and Point Bars	Deposition develops a floodplain just as erosion makes valleys. Floodplain is a major landform of river deposition. Large-sized materials are deposited first when the stream channel breaks into a gentle slope. Thus, normally, fine-sized materials like sand, silt, and clay are carried by relatively slow-moving waters in gentler channels usually found in the plains and deposited over the bed and when the waters spill over the banks during flooding above the bed. Natural levees are found along the banks of large rivers. They are low, linear, and parallel ridges of coarse deposits along the banks of rivers, quite often cut into individual mounds. Point bars are also known as meander bars. They are found on the concave side of meanders of large rivers and are sediments deposited in a linear fashion by flowing waters along the bank.

The study of running water in the evolution of landforms helps us understand and appreciate the diversity of landforms on the surface of the earth.