Geoscience Reference
In-Depth Information
Chapter 4
Surface Run-off, Soil Erosion and Slope
Instability
Abstract The dynamic nature of a landscape results from the interaction of surface
run-off with rocks and soil being guided by geo-hydrologic variables. The estimation
of surface run-off and its better understanding reveals a clear idea about the degree
and amount of surface erosion and slope vulnerability over the space. In this chapter
Soil Conservation Service (SCS) Run-off Curve Number (CN) model proposed by
United State Department of Agriculture (USDA 1972) is used to determine the
surface run-off from six individual sub-watersheds for predicting the periodical
spatial distribution of slope instability and soil erosion. The determined Curve
Number (CN) under antecedent moisture condition-III (AMC-III) for sub-watershed
I, II, III, IV, V and VI are 85.02, 73.52, 87.36, 87.76, 85.57 and 89.85 respectively.
Sub-watershed I contributes maximum run-off from a rainfall of 90.5 mm
(4,52,359.4 m
3
) which is followed by VI, III, IV, V and II. Landslide Potentiality
Index Value (LPIV) is derived for each watershed which reveals that Sub-watershed
I and VI is the signi
cant landslide prone unit of the study area. Finally, considering
both run-off and LPIV an instability scale has been made which reveals that Sub-
watershed VI, I and III have to be paid more attention for a proper management of
land, water and soil during the months of July, August and September. All the
necessary constructions, plantation and related preparedness through raising
awareness and making task forces during pre-monsoon dry period are of utmost
importance for managing landslip and soil erosion at Shivkhola Watershed.
4.1 Introduction
Runoff, being the most important hydrologic variable, draws the attention of
hydrologists, water resource planners, local govt. etc. for water resource planning
and applications. The objective mostly sought by hydrologists is the accurate and
timely prediction of runoff of a given point in a drainage basin by either using a range
of equation and models or direct measurement at gauging station. The stream
measuring stations are more common in large river system and reservoirs where
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