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Introduction
Watershed is defined as “Natural Hydrologic entity that cover a specific area expanse of land surface from which the runoff (due to rainfall) flows to a defined drain, channel, stream or river at any particular point”. Watershed modelling implies the proper use of all land, water and natural resources of a watershed for optimum production with minimum hazard to eco-system and natural resources. Therefore, an integrated approach to watershed modelling is insisted for sustained development of water resources.

In watershed modelling collection data and its availability is a major task especially in developing countries. This study aims to provide an integrated approach to watershed modelling from the commonly available data on watersheds. From the review of literature it is found that both surface water and soil erosion were alone integrated and studied. But it is necessary to include all the components of a watershed to formulate a proper and efficient watershed modelling. Based on this point of view, an integrated approach to watershed modelling for sustainable development of water and land resources is attempted. Remote sensing and Geographic Information System (GIS) place a vital role in watershed modelling and planning. This research work used conventional methods as well as remote sensing and GIS for data collection and analysis.

The major problem in water shed is degradation and the main causes for such degradation are:

• Changing of land use from forest into pasture, agriculture and urban, as a result of population growth and general scarcity.
• Use of the wood as a source of heat and energy in economically poor area.
• General degradation of forests caused by industrial growth, Environmental pollution, and increase of consumption.

Objectives of The Study
The overall objective of this study is to address the ecostatus using GIS and to arrive at watershed modeling for the Kundapallam

• To identify the causes for eco degradation at Kundapallam
• To quantify the impact factors and prepare the Environmental Sensitivity Matrix.
• To validate the areas prone for erosion with landslide analysis
• To prepare a model for watershed analysis and landslide

Description of The Study Area
Kundapallam (Kd1) micro watershed lies in the Nilgiris district of TamilNadu which is a hilly district located on the fragile environment of Western Ghats with an elevation ranging from 300 m in the Mayor Gorge to 2634 m above MSL at Doddabetta peak. Kundapallam (kd1) micro watershed has a geographical area of 12 sq.km and is bounded by 76° 35’ 30” and 76° 37’ 30” East longitude and 11°14’15”and 11°16’15”North latitude. It consists of forest plantation (4.04%), Shola lands (6.35%), Uplands i.e., Land with or without scrubs (9.38%), water bodies (3.03%), Grass land (1.59%), Mixed land cover (5.34%) and built up area (2.16%).

The climatic conditions of the Kundapallam Watershed are

• Wind velocity – 5.4 km/hr
• Relative Humidity – 77%
• Annual Rainfall – 1300-2000 mm
• Maximum Temperature – 24.3°C (summer season)
• Minimum Temperature – 6.0° C (winter season)

Base Map of Study area:



Methodology:
The methodology used is illustrated in the figure - 2


Fig – 2: Over all Methodology

RESULT AND DISCUSSION

Vegetation Factor
The conformity analysis was carried out in two steps. The first step comprised of delineating the total area land into different suitability classes (1994 and 2004). In the second stage, satellite data (2004) was overlaid and the area extent of different categories were delineated and quantified.

Category	Area ha.
Highly prone for degradation	81.7475
Moderately prone for degradation	11.4008
Ecologically stable area	1386.6535

Runoff estimation
The annual rainfall is taken for computation of the precipitation. Next the losses or abstraction grouped broadly under evaporation, evapo-transpiration and infiltration are determined. This is achieved by determining the product of the area of land cover unit and its loss index factor expressed in terms of rainfall. The areas of land cover unit are readily available from land cover maps. Subtracting the total loss from the total precipitation value finally arrives at the runoff quantity.

	1994	2004
Total precipitation	2395	1887.32
Evapotranspiration Loss	966.85	954.36
Evaporation Loss	1.19	1.19
Infiltration Loss	45.67	38.45
Runoff	1381.27 Ha.m	893.31

The runoff was also computed by Curve Number technique. The runoff estimated considering the annual rainfall workout to be 903.48mm by curve technique

Estimation of soil erosion

S.No	Type of model	Soil loss in 1994 tons/ha/year	Soil loss in 2004 tons/ha/year
1	Musgrave’s	81	80.79
2	RUSLE	67.03	55.72
3	MUSLE	119.91	66.28
4	STEHLIK	138.59	168.54

Environmental sensitivity analysis
Cumulative Weightage of Environmental Character Matrix,
CWEC (1994) = 3638.161 CWEC (2004) = 6398.514


Fig 3: Sensitivity Map

Sensitivity Classes	1994	2004
Highly Sensitive	Agricultural Land, Degraded Forest, Grassland, Horticultural or Plantation & Landwith or without Scrubs.	Agricultural Land, Degraded Forest, Dense Forest, Horticultural or Plantation, & Land with or without Scrubs
Medium Sensitivity	Dense Forest, Forest Plantation & Open Forest	Forest Plantation, Grass Land, Village
Low Sensitivity	Village	Open Forest

Conclusions

• From the land use map 2004 it is observed 12% of the dense forest area (i.e., 63 ha.) is converted into Horticulture or plantation (34 ha.), Agricultural area (22 ha.) and Village (7 ha.). From the statistics prevailing during 2004, land use map indicates that the urbanization and human impacts are the major cause for the degradation.
• The runoff is very low in 2004 as the annual rainfall in 2004 (1280.4mm) is low when compared to that of 1994 (1625mm).
• The runoff estimated considering the annual rainfall workout to be 903.48mm by curve technique. This shows that the runoff curve number with an initial abstraction of 0.3 can be used as such for the Kundapallam watershed.
• Musgrave’s equation is used to compute the topsoil loss 2.5% of the total area (degraded forest) is under very high prone for soil loss.. 65.81% of total area (dense forest and horticultural plantation) is under high prone for soil loss. 2% of total area (Village) is under medium prone for soil loss. 30.27% of total area (agricultural land, forest plantation, grassland, land with or with out scrub and open forest) is under low prone for soil loss. Since the soil is covered with crops the topsoil loss is very low.
• RUSLE is used to calculate the gross erosion in the Kundapallam watershed.. The erosion is low in 2004 compared to that of 1994 as the amount of rainfall is less in the year 2004 (1280mm) compared to that of 1994(1625mm).
• MUSLE is used to calculate the sediment yield in the Kundapallam watershed.. The volume of runoff and peak flow rate is the most dominating factor in the computation of sediment yield. The sediment value is very low in 2004 as the runoff and peak flow rate was also comparatively low when compared to that of 1994.
• The 4th soil loss model adopted was Stehlik. It is used to calculate the soil loss. The soil loss was found out to be 138.5977 ton/ha/year in 1994 and 168.54 tons/ha./year in 2004. On October 23rd2004a major landslide occurred in Kundapallam watershed measuring about 159.3 tons/ha/yr. The gross erosion of the Kundapallam watershed was found to be 168.54 tons/ha/yr, which works out to be almost closer.
• Since the area of percentage of village in 1994 is 1.428% and for 2004 it is 1.95%. There is drastic increase in the percentage of area, which results in increase in sensitivity from 1994 to 2004.
• Medium sensitivity for 1994 is 34.68% and it has been decreased to 4.37% for 2004 due to the decrease in the Village area.

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