Question

How is the rate of erosion affected by runoff ?
a)Runoff increases the rate of erosion
b)Runoff decreases the rate of erosion
c)Runoff does not affect the rate of erosion
d)Runoff lessons erosion Mountainous regions

Answer 1

@LTM

Answer 2

http://www.waterencyclopedia.com/Re-St/Runoff-Factors-Affecting.html
I'M NOT SURE BUT YOU CAN LOOK ON THE WEBSITE OR READ THE BOTTOM FOR IT
EFFECTS OF RUNOFF ON EROSION AND SOIL AND WATER RESOURCES

There is a pronounced relationship between rate of runoff and incidence of erosion. Runoff water has the energy to detach soil particles by scour and to transport entrained soil materials either in suspension or by pushing or rolling larger particles. In this way overland flow causes erosion. Erosion by scouring accounts for less than 10% of the erosion process, the rest being caused by raindrop impact. Secondary forms of erosion resulting from the transporting effects of runoff are more damaging and are usually classified as rill, gully and stream channel erosion according to increasing concentration of runoff and the degree of damage caused to land. Runoff erosive capacity is a function of its volume and velocity; as the volume and velocity increase, so do the energy to scour away soil particles and the load-carrying capacity or transportability. Doubling the velocity of runoff increases its scouring capacity and transportability to the fifth and sixth powers, respectively (Shaxson et al. 1977).

The consequences of runoff and erosion are the impairment of the quality and productivity of the land, both that eroded and that receiving soil material from upslope. Erosion results in the decline of soil fertility as a result of loss of topsoil and nutrients, loss of organic matter and clay and the consequent loss of the soil's capacity to retain nutrients and water. It can also result in the compaction and sealing of soil surface giving lower infiltration rates and increased runoff. There are many areas in the world where erosion has led to serious impoverishment of the land and rendered it unusable for crop production. Erosion is a great cause of concern in the developing world as a whole. Runoff, wherever it occurs, results in washing away of crops and fertilizer inputs, loss of soil moisture and recharge capacity, so consequently there is frequent drought stress in crop production. Runoff, as it increasingly concentrates in drainage lines, can build up and cause severe physical damage down-slope including the washing away of roads, bridges, buildings and the development of dangerous gullies. The effects of extreme runoff are usually visually emphasised by the development of gully systems along which the erosion is concentrated. Deposition of particles carried by runoff causes channel sedimentation, silting up and pollution (by nutrients, pesticides and toxic chemicals) of dams and reservoirs and flooding and sedimentation of bottomlands.

Most arable systems, especially those involving complete tree clearances, mechanical tillage and continuous cultivation, disturb the surface soil and expose it to the weather, so making the land liable to serious runoff and erosion. Deforestation by mechanized systems followed by plough-based tillage, for example, causes severe runoff and erosion (Table 1). Runoff and erosion under such systems can be very substantial and seriously limit crop production. Appropriate runoff management techniques that enhance water conservation and reduce erosion to acceptable rates will minimize these effects.