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INTERNATIONAL JOURNAL OF ENVIRONMENTAL SCIENCES Volume 1, No 7, 2011 © Copyright 2010 All rights reserved Integrated Publishing Association Research article ISSN 0976 – 4402 Received on April 2011 Published on July 2011 1978 Spatial Information Technology as a tool for soil erosion assessment using USLE A study in the Shendurney Wild Life Sanctuary, South Kerala, India Smitha Asok.V 1 , Sobha V 2 1 Department of Environmental Sciences, University of Kerala, Thiruvananthapuram 2 – ‘Sreemangalam’, GGRA85, V. V. Road, Pettah, Trivandrum695024. [email protected] ABSTRACT Spatial Information Technology coupled with Universal Soil Loss Equation has proved to be an effective tool in the assessment of Soil erosion from an area. Soil, which is the primary resource of any Protected Area, needs to be conserved for its scientific management. Shendurney Wildlife sanctuary, one of the most biodiversity rich areas in the Western Ghats is endowed with a multitude of floral and faunal wealth. The USLE comprising of the five factors viz. R, K, LS, C and P is employed for the quantification of the soil loss from the Sanctuary. The results of the study helps to identify the areas prone to soil erosion in four categories namely severe, high, moderate and low. The low and medium category erosion class together comprises about 92.96 % of the total sanctuary area, whereas the high and severe category erosion class constitutes about 4.8 % of the sanctuary. These erosion hotspots have been identified and demarcated where location specific soil conservation methods need to be implemented. The effectiveness of the application of such a study can be further endorsed by its vital utility in formulating the Action Plan for the conservation measures to be adopted in the Sanctuary. Keywords: USLE, Shendurney WLS, Spatial Information Technology, PA Management 1. Introduction Shendurney Wildlife Sanctuary, part of Agasthyamalai Biosphere Reserve is one of the richest areas of biodiversity in the Western Ghats. The biotic richness and distinct biographic features of this forest area makes it an ideal gene pool reserve. The etymological meaning of the name Shendurney have been derived from a tree locally called ‘Chenkurinjy’ (Gluta travancorica) which is an endemic tree confined to this tract. Shendurney Wildlife Sanctuary has substantial natural vegetation ranging from southern secondary moist mixed deciduous forest to southern subtropical hill forest. Tropical evergreen and semievergreen forest comprises three forth of the total area of the sanctuary. The undulating terrains, rocky mountains, waterfalls, grasslands etc form the habitat of a variety of tropical flora and fauna. The construction of the Parappar dam has resulted in the creation of an artificial lake of about 18.69 sq.km within the sanctuary. The sanctuary is located in Kollam district and comes under the control of Agasthyavanam Biological Park circle. The total area of the sanctuary comes to about 171 sq.km. The sanctuary is situated about 68 km from Kollam and 72 km from Thiruvananthapuram city on N H 208.

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INTERNATIONAL JOURNAL OF ENVIRONMENTAL SCIENCES Volume 1, No 7, 2011

© Copyright 2010 All rights reserved Integrated Publishing Association

Research article ISSN 0976 – 4402

Received on April 2011 Published on July 2011 1978

Spatial Information Technology as a tool for soil erosion assessment using USLE ­ A study in the Shendurney Wild Life Sanctuary, South

Kerala, India Smitha Asok.V 1 , Sobha V 2

1­Department of Environmental Sciences, University of Kerala, Thiruvananthapuram 2 – ‘Sreemangalam’, GGRA­85, V. V. Road, Pettah, Trivandrum­695024.

[email protected]

ABSTRACT

Spatial Information Technology coupled with Universal Soil Loss Equation has proved to be an effective tool in the assessment of Soil erosion from an area. Soil, which is the primary resource of any Protected Area, needs to be conserved for its scientific management. Shendurney Wildlife sanctuary, one of the most biodiversity rich areas in the Western Ghats is endowed with a multitude of floral and faunal wealth. The USLE comprising of the five factors viz. R, K, LS, C and P is employed for the quantification of the soil loss from the Sanctuary. The results of the study helps to identify the areas prone to soil erosion in four categories namely severe, high, moderate and low. The low and medium category erosion class together comprises about 92.96 % of the total sanctuary area, whereas the high and severe category erosion class constitutes about 4.8 % of the sanctuary. These erosion hotspots have been identified and demarcated where location specific soil conservation methods need to be implemented. The effectiveness of the application of such a study can be further endorsed by its vital utility in formulating the Action Plan for the conservation measures to be adopted in the Sanctuary.

Keywords: USLE, Shendurney WLS, Spatial Information Technology, PA Management

1. Introduction

Shendurney Wildlife Sanctuary, part of Agasthyamalai Biosphere Reserve is one of the richest areas of biodiversity in the Western Ghats. The biotic richness and distinct biographic features of this forest area makes it an ideal gene pool reserve. The etymological meaning of the name Shendurney have been derived from a tree locally called ‘Chenkurinjy’ (Gluta travancorica) which is an endemic tree confined to this tract. Shendurney Wildlife Sanctuary has substantial natural vegetation ranging from southern secondary moist mixed deciduous forest to southern subtropical hill forest. Tropical evergreen and semi­evergreen forest comprises three forth of the total area of the sanctuary. The undulating terrains, rocky mountains, waterfalls, grasslands etc form the habitat of a variety of tropical flora and fauna. The construction of the Parappar dam has resulted in the creation of an artificial lake of about 18.69 sq.km within the sanctuary. The sanctuary is located in Kollam district and comes under the control of Agasthyavanam Biological Park circle. The total area of the sanctuary comes to about 171 sq.km. The sanctuary is situated about 68 km from Kollam and 72 km from Thiruvananthapuram city on N H 208.

Spatial Information Technology as a tool for soil erosion assessment using USLE ­ A study in the Shendurney Wild Life Sanctuary, South Kerala, India

Smitha Asok V, Sobha V.

International Journal of Environmental Sciences Volume 1 No.7, 2011 1979

Statement of significance

The significance of the sanctuary lies in its ecological, faunal, floral, and geomorphological importance. Various factors contributing to the significance of the area are as indicated below.

1. Abundance of Gluta travancorica, an endemic species of Agasthyamalai region. 2. It is a treasure house of plant diversity. About 951 species of flowering plants

belonging to 150 families are reported from this sanctuary of which, 309 species are endemic to Western Ghats.

3. Occurrence of more than 100 species of threatened plants within the sanctuary which is the type locality of several endemic and threatened species

4. Presence of wild populations of Lion Tailed Macaque, a highly endangered species. 5. Presence of other wild animals like Elephant, Tiger, Leopard, Bear, Nilgiri Langur,

Malabar squirrel etc 6. High degrees in diversity of avifaunal wealth ­ 245 species of birds were reported

including migratory, endemic and endangered species. 7. The watershed of Kallada reservoir roughly coincides with the boundary of the

sanctuary and is an important source of water for irrigation purpose to the districts of Kollam and Pathanamthitta.

8. As part of the Agasthyamalai Biosphere Reserve, the sanctuary has an important role to play in conserving the rich biodiversity.

9. Presence of unique vegetation of Myristica swamps. 10. The first ecotourism project in India, Thenmala ecotourism project making use of land

and water area of the sanctuary add color to the prominence of the sanctuary, its role in the nature education and promoting ecologically sustaining tourism.

The locale ­ in detail

The tract dealt with is in the western slope of Western Ghats in the taluk of Pathanapuram in Kollam revenue district and lies within 76° 59’ 30” and 77° 16 30” East longitude and 8° 44’ and 9° 14’ North latitude. This area lies south of Aryankavu Valley and stretches to a length of about 25 km east­west. The sanctuary is situated about 68 km from Kollam and 72 km from Thiruvananthapuram city.

The main river in the ridge is Shendurney River and its tributaries. These are Umayar, Parappar, Uruliyar, Pasmankandamthodu etc. Other watercourses that drain the area are the Ambady and Choodal streams which join the main river near Kulathupuzha at Naduvannurkadavu. The whole area is hilly in character with a gentle slope towards the west. The eastern portion near the high hills is very irregular being interspersed with ravines. There is a series of high peaks protruding from the main ridge, the highest of which is Alvarkurichy peak (1550 m). Upper slopes are rugged, steep and inaccessible at many places.

The underlying rocks are metamorphic consisting of Charnockite and other gneisses. In the main ridges and slopes there are intrusions of huge masses of rocks of granitic nature that are sometimes covering a considerable area in the most rugged form.

The following are the important soil associations seen in the study area.

Spatial Information Technology as a tool for soil erosion assessment using USLE ­ A study in the Shendurney Wild Life Sanctuary, South Kerala, India

Smitha Asok V, Sobha V.

International Journal of Environmental Sciences Volume 1 No.7, 2011 1980

1. Channapettah – Bharathipuram ­ Thingalkarikkakom soil association

2. Karavalur­Edamulackal­Vilakkudy soil association 3. Moozhiyar soils

4. Nedumpara­ Gudarakkal­ Channapettah soil association

As per the classification of Gadgil and Meher Homji (1982), the vegetation of Shendurney wildlife sanctuary comes under the bio geographic region of wet evergreen forests of West­ coast Western Ghats and plesioclimax of Cullenia­Mesua­Pallaquium. The following forest types are identified in this sanctuary as per the revised survey of the forest types of India by Champion and Seth (1968).

1. West­coast tropical evergreen forest 2. West­coast tropical semi evergreen forest

3. Southern hilltop tropical evergreen forest 4. Southern subtropical hill forest

5. Southern secondary moist mixed deciduous forest 6. Reed brakes

7. Myristica swamps 8. Grasslands

Terrain evaluation and biodiversity

While tropical ecosystems purify the air, regulate water movement and act as controlling factors for global climatic changes, it actually provide conducive atmosphere for genetic and species diversity of biotic components. The sustenance and diversity of biota is in fact strongly dependant on the health of its surrounding environment in terms of climate, soil, hydrological system and so on. Hence a stock­ taking exercise on the nature of terrain parameters is essential for developing comprehensive plans for long term biodiversity conservation. Since the area of land portion available for natural sustenance is meager due to intense anthropogenic requirements, the care taken for environmental monitoring in such Government Protected Areas (PAs) is extremely high. In this perspective, this study assumes special importance. Long term management of forests should be formulated on the basis of geo­scientific data for the sustenance of ecosystem as a whole.

Since, the boundary of the sanctuary coincides with the Catchment area of the Kallada reservoir, special emphasize need to be given on the principles of watershed management of Shendurney River, which in turn is the Catchment of Kallada reservoir. Catchment degradation in terms of soil loss, nutrient loss, reduction in water holding capacity etc. on which depend the faunal and floral changes is strongly reflected on the terrain parameters and their evolutionary changes takes place over a period of time. Here, the Shendurney wildlife sanctuary has been selected as a model area for such an investigation to suggest recommendations for terrain corrections with a view to conserve this part of our forested ecosystem. The present study aims to undertake an estimation of soil loss in the study area using the Universal Soil Loss Equation (USLE).

Spatial Information Technology as a tool for soil erosion assessment using USLE ­ A study in the Shendurney Wild Life Sanctuary, South Kerala, India

Smitha Asok V, Sobha V.

International Journal of Environmental Sciences Volume 1 No.7, 2011 1981

2. Materials and Method

This study specifically addresses the assessment of soil erosion in the Catchment of River Shendurney using the tools of Remote Sensing and Geographical Information System. The data sources used for the study were the Survey of India Toposheet 1977(1:50K) and Indian Remote Sensing Satellite IRS­ P6 (23.5) LISS III imagery 2006 substantiated with field data. The collected data were further processed and analyzed using the software Arc VIEW 3.2, Erdas Imagine 8.7 and Arc GIS 9.2.

The Universal Soil Loss Equation, USLE, developed by Wischmeier and Smith (1978) is used in this study for estimation of soil loss. Soil loss quantification for the entire sanctuary is calculated by generating various input factors of USLE in GIS environment. The USLE is based on the following factors that are used to compute the mean annual soil loss:

A = R ⋅ K ⋅ L ⋅ S ⋅C ⋅ P …. (i)

Where: A = Mean annual soil loss

R = Rainfall erosivity factor K = Soil erodibility factor

L = Slope length factor S = Slope factor

C = Cover factor and P = Management factor

Methodology used to compute each contributing factor is as follows:

R Factor

Among the different parameters that affect the erosion of soil, precipitation plays a vital role. Factor R in the USLE is an erosion index, which is the product of total energy (E) of storm and the maximum intensity of 30 minutes rainfall event (I30). In the present work daily rainfall data of 10 years (2000­2009) were analyzed for computing minimum erosion index (EImin) using the procedure suggested by Richardson et al (1983). This model is useful for quick computation of erosion index from daily rainfall data for any particular month or season for any river basin. The minimum EI that can result from a daily rainfall event of amount P would occur during a rainfall of uniform intensity for the full 24 hour period as suggested by Richardson et al (1983).

EImin=P 2 (0.00364log10P­0.00062) …. (ii)

where P is the daily rainfall in mm.

K factor

Soil erodibility (K) defines the inherent resistance of the soil to both detachment and transport. The parameters namely soil texture, structure, permeability and organic matter content determines the erodibility of a particular soil. Soil samples collected from 30 locations in the study area were analyzed for various physico­chemical and textural

Spatial Information Technology as a tool for soil erosion assessment using USLE ­ A study in the Shendurney Wild Life Sanctuary, South Kerala, India

Smitha Asok V, Sobha V.

International Journal of Environmental Sciences Volume 1 No.7, 2011 1982

parameters and K factor values were accordingly estimated from the soil erodibility nomograph (Wischmeier and Smith, 1978) derived from the equation:

K= (2.1*10 ­4 (12­%OM) (M) 1.14 ) +3.25(S­2) +2.5(P­3) ….. (iii)

100

Where OM = Organic Matter (%); M= (%Silt+%Fine sand) (100­%Clay); S=Soil structure code (very fine granular=1, fine granular=2, coarse granular = 3, blocky, platy or massive=4); P=permeability class (rapid=1, moderate to rapid=2, moderate=3, slow to moderate=4, slow=5, very slow=6)

LS factor

The topographic factors i.e. slope gradient and length of slope significally influences soil erosion by surface water movement. The slope of the study area was derived from the DTM based on the toposheet derived contour data at 20m interval.

Slope length in meters (L) is calculated from the Flow Accumulation and Slope steepness in percentage factors. The LS factor is calculated using modification of the empirical equation (Wischmeier and Smith, 1978) from slope length and slope percent using Raster Calculator tool of the Arc GIS Spatial Analyst. (Engel, 2003)

LS = [flow acc*cellsize/22.13] 0.4 * [(sin (slope*3.14/180))/0.0896] 1.3 …. (iv)

C Factor

Vegetation cover is, after topography, the second most important factor that controls soil erosion. In the USLE, the effect of vegetation cover is incorporated in the cover management factor (C factor). It is defined as the ratio of soil loss from land cropped under specific conditions to the corresponding loss from clean tilled, continuous fallow (Wischmeier and Smith, 1978).

In undisturbed forest areas like Shendurney, infiltration rates and the organic matter content are high and much or the entire surface are usually covered by decaying forest duff which shield the forest soil from soil erosion. The thick canopy cover adds to this and the C Factor values were assigned based on the specific characteristics of duff cover and canopy density.

P factor

Factor P in the USLE is ratio of soil loss with a specific supporting practice to the corresponding loss with up and down cultivation. Since, in the present study no erosion control measures were identified within the sanctuary, a constant value of 1 is assigned. (Wischmeier and Smith, 1978 and S Lee, 2003)

3. Results and discussion

The daily rainfall data was collected from three rain gauge stations viz. Aryankavu, Kulathupuzha and Shendurney for a period of ten years from 1999 to 2008. The collected

Spatial Information Technology as a tool for soil erosion assessment using USLE ­ A study in the Shendurney Wild Life Sanctuary, South Kerala, India

Smitha Asok V, Sobha V.

International Journal of Environmental Sciences Volume 1 No.7, 2011 1983

data was further processed to obtain the R Factors using the equation (ii) and the R Factors for these three locations were found to be 708.608, 1125.443 and 910.653 respectively. The R Factors obtained were brought into ArcGIS and the point data was interpolated to obtain the R Factor map of the study area which is given in Fig.1.

Soil samples collected from different vegetations of the study area was analyzed for determination of the physico­chemical parameters. The organic matter content, soil texture classes and the permeability and soil structure classifications were substituted in equation (iii) to obtain the K Factor values. These point data was also brought into ArcGIS and interpolated to obtain the K Factor map which is given in Fig. 2

Physiographic map of the study area was prepared with a 20 m contour interval from the Toposheet of 1:50,000 scale from which the Digital Terrain Model of the study area was developed using the 3D Analyst extension of ArcGIS. This is given in Fig. 3. The slope length and slope percentage values were obtained from the DTM and substituted in Equation (iv) to develop the LS Factor map of the study area as shown in Fig. 4.

The original C Factor values ranges from 0 for full cover to 1 for bare soil and a Look Up Table (LUT) was generated for the present study based on the specific characteristics of duff cover and canopy density. The C Factor values were assigned using the LUT given in Table.1. The resultant C Factor map of the study area is shown in Figure 5.

Table 1: Look Up Table for C Factor values Land Cover C Factor West Coast Evergreen Forest 0.002 West Coast Semi­evergreen Forest 0.003 Southern Secondary moist Deciduous Forest 0.006 Hill Top Evergreen Forest 0.004 Grassland 0.015 Reed Brake 0.009 Bentinkia Condappana Brake 0.011 Phyllanthus Embilica Brake 0.007 Enclosure 0.100 Excluded Area 0.088 Treatment Area 0.005

Spatial Information Technology as a tool for soil erosion assessment using USLE ­ A study in the Shendurney Wild Life Sanctuary, South Kerala, India

Smitha Asok V, Sobha V.

International Journal of Environmental Sciences Volume 1 No.7, 2011 1984

Figure 1: R Factor map of Shendurney Wildlife Sanctuary

Figure 2: K Factor map of Shendurney Wildlife Sanctuary

Spatial Information Technology as a tool for soil erosion assessment using USLE ­ A study in the Shendurney Wild Life Sanctuary, South Kerala, India

Smitha Asok V, Sobha V.

International Journal of Environmental Sciences Volume 1 No.7, 2011 1985

Figure 3: Digital Terrain Model of Shendurney Wildlife Sanctuary

Figure 4: LS Factor map of Shendurney Wildlife Sanctuary

Spatial Information Technology as a tool for soil erosion assessment using USLE ­ A study in the Shendurney Wild Life Sanctuary, South Kerala, India

Smitha Asok V, Sobha V.

International Journal of Environmental Sciences Volume 1 No.7, 2011 1986

Figure 5: C Factor map of Shendurney Wildlife Sanctuary

Figure 6: Soil Erosion Assessment map of Shendurney Wildlife Sanctuary

Spatial Information Technology as a tool for soil erosion assessment using USLE ­ A study in the Shendurney Wild Life Sanctuary, South Kerala, India

Smitha Asok V, Sobha V.

International Journal of Environmental Sciences Volume 1 No.7, 2011 1987

The P Factor of the study area was assumed to be 1 since no erosion control measures were found inside the sanctuary and also since the majority of the area consisted of dense evergreen forests.

All the above Factors were substituted in the Universal Soil Loss Equation (i) to get the Mean Annual Soil Loss from the study area and the resultant map is shown in Fig.6. Soil Erosion classes were given in severe, high, moderate and low categories and from the map it can be seen that the majority of the area 13397 ha. (86.04% of the total area) falls under the low erosion classification (< 5 tons/ha/yr). Second in rank comes the moderate soil erosion class (5­25 tons/ha/yr) which constitutes about 1079 ha (06.92%). High erosion class (25­50 tons/ha/yr) falls over an area of 217 ha. (01.39%). Severe soil erosion class (50 – 209.89 tons/ha/yr) covers an area of 532 ha (03.41% of the total study area). The results are presented in Table 2.

Table 2: Results of the analysis

Soil Erosion Class Soil Erosion Quantity (tons/ha/yr)

Area Covered (ha)

% of total area

Low < 5 13397 86.04% Medium 5­25 1079 06.92% High 25­50 217 01.39% Severe 50­210 532 03.41%

Thus annually an average quantity of 5.65 tons/ha of soil gets eroded from the Shendurney Wildlife Sanctuary. The USLE thus proves to be an efficient tool in the assessment of soil erosion in this area.

4. Conclusion An attempt has been made to estimate the soil loss in Shendurney Wild Life

Sanctuary using the Universal Soil Loss Equation in the GIS environment. The results obtained helps to identify the areas prone to soil erosion in four categories namely severe, high, moderate and low. The effectiveness of the application of such a study can be further endorsed by its vital utility in formulating the Action Plan for the conservation measures to be adopted in the Sanctuary. Moreover, this study shows that GIS and Remote Sensing based analysis offers an optimal method for soil loss estimation of an area in an effective and accurate manner. Terrain information for biodiversity conservation is a relatively new concept and such an approach for ecosystem management is relatively new in the Kerala context. This becomes specifically valuable in the perspective of the Conservation and Management of the Protected Areas (PAs) in the country.

Acknowledgement

Deeply indebted to my Guide and Supervisor Dr. V. Sobha, whose guidance and blessings has enabled me to successfully attain this venture. Also grateful to my friends and family for the immense help and support they have rendered during the completion of this work.

Spatial Information Technology as a tool for soil erosion assessment using USLE ­ A study in the Shendurney Wild Life Sanctuary, South Kerala, India

Smitha Asok V, Sobha V.

International Journal of Environmental Sciences Volume 1 No.7, 2011 1988

5. References

1. Bernie Engel, 2003. Estimating Soil Erosion Using RUSLE using Arc View. http://pasture.ecn.purdue.edu/~abe526/ resources1/ gisrusle/gisrusle.html as on 7th May, 2011.

2. Cooley, K.R., 1980. Erosivity values for individual design storms. Journal of Irrigation and Drainage Division, Proceedings of the American Society of Civil Engineers, 106 (IR2), pp135­144.

3. Champion, H. G. and Seth, S. K., 1968. A Revised Survey of the Forest Types of India, Government of India Publications, New Delhi.

4. Gadgil M. and Meher Homji V. M., 1982. Conserving India’s Biological Diversity: Indo­US Binational workshop on Conservation of Biological Diversity, Department of Environment, Government of India, New Delhi.

5. Jude Emmanuel, 2008. Ecological study of Neyyar Wildlife Sanctuary with special emphasis on arborescent species. PhD Thesis, University of Kerala.

6. Kerala Forest Department, Shendurney Wildlife Sanctuary­Management Plan 2002­ 12.

7. Moore, I and G Burch. 1986a. Physical basis of the length –slope factor in the Universal Soil Loss Equation. Soil Science Society of America Journal, 50, pp 1294­ 1298

8. Richardson C.W et al., 1983: Estimation of Erosion Index from daily rainfall amount. Transactions of the ASAE. 26(1), pp 153­156,160.

9. Saro Lee, 2003. Soil Erosion Assessment and its verification using the Universal Soil Loss Equation and Geographic Information System: A case study at Bourn, Korea. Published online. Springer­Verlag.

10. Van Der Knijff et al., 1999. Soil Erosion Risk Assessment in Italy. European Soil Bureau, EUR 19022 EN, p 52.

11.Wischmeir, W.H and D.D. Smith, 1978. Predicting Rainfall Erosion losses­ A guide to Conservation Planning. USDA Agric. Handbook No.537.p 19­20.