Question
Running water is by far the most dominating geomorphic agent in shaping the earth's surface in humid as well as in arid climates. Explain.
Solution
Running water is the main denudational agent, eroding and transporting sediments and actively shaping the landforms. It acts through process of attrition, vertical and lateral erosion and deposition to shape earth’s surface.
In humid regions, there are two components of running water.
1. One is overland flow on general land surface as a sheet.
2. Another is linear flow as streams and rivers in valleys.
During youthful stage a number of erosional forms are developed by the running water such as U-shaped valleys, gorges, canyons etc. With time, stream channels over steep gradients turn gentler due to continued erosion, and as a consequence lose their velocity, facilitating active deposition. During their terminal stages i.e. old stages, the running water makes deltas. During the middle stages, a number of landforms like river terraces, alluvial fans, flood plains , natural levees etc. are formed.
In arid regions, though rain is scarce, it comes down torrentially in a short period of time. The desert rocks devoid of vegetation, exposed to mechanical and chemical weathering processes due to drastic diurnal temperature changes, decay faster and the torrential rains help in removing the weathered material very easily.
The weathered material debris in deserts is not only moved by winds but also by rain/sheet wash. Thus, we can say that the running water is by far the most dominating geomorphic agent in shaping the earth's surface in humid as well as arid regions.
