Land and Watershed Management - Practices of Irrigation and On-farm Water Management - page 225

maximum length of run of individual plot is 200 m. No additional mulch is applied
in the field. The 2-yr 6-h rainfall for the area is 40 mm. Estimate the soil loss from
the field.

Solution

We know soil loss, A = R × K × LS × C × P (t/ha/yr)

We get rainfall and runoff factor,

R = 0.417 P 2.17

where P is the 2-yr, 6-h rainfall amount.
Given, P =40mm
Then, R

[40] 2.17

= 0.417 × = 1, 249

Assumed values of other factors (along with their conceptual judgment and typical
values) are summarized below:

Factor Relevant field condition Typical values Assumed value

K (Soil erodibility factor) The soil is silt-loam 0.013-0.053 0.02

LS (Slope length and
steepness factor)

Slope length 200 m,
slope 1%

0.2-6.0 1.0

C (Cover and management
factor)

Crops are wheat and rice,
dense coverage

0.01-1.4 0.2

P (Support practice factor) No mulching 0.3-0.9 0.4

Putting the values,

A = 1, 249 × 0.02 × 1.0 × 0.2 × 0.4 = 1.99 t/ha/yr (Ans.)

6.5.7 Erosion and Sedimentation Control

Sedimentation involves the following geologic processes: erosion, transportation,
and deposition. These are natural geologic phenomena. However, land development
and other man-made activities accelerate the process. Excessive sediment loads
result in turbid waters and heavy deposition over the substrate. Sediment-laden
waters affect human activity through degradation of water quality. Consequently,
minimizing the occurrence of erosion and effective control of sediment transport is
imperative.
Principles of erosion and sedimentation control are based on minimizing the
effects of the soil and climatological factors (described earlier) that accelerate the
erosion process. Any single strategy may not be able to control those factors nor
can they all be performed at every site. However, adoption/integration of as many