INTEGRATED ANALYTICAL HIERARCHY PROCESS MODELING OF WATERSHEDS FOR ENVIRONMENTALLY SUSTAINABLE DEVELOPMENT

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1 INTEGRATED ANALYTICAL HIERARCHY PROCESS MODELING OF WATERSHEDS FOR ENVIRONMENTALLY SUSTAINABLE DEVELOPMENT Rao Kumar Raghavendra 1 1 Professor & Head, Department of Civil Engineering, New Horizon College of Engineering, Bangalore, Karnataka, INDIA ABSTRACT generated during the raster analysis can be integrated for site suitability analysis to locate conservation structures. The environmentally sustainable development of watersheds can be ascertained for the different watersheds The site suitability evaluation for various conservation in which integrated watershed based conservation measures can be obtained by using criteria norms specified measures have been suggested for conserving soil and water. In this context the Analytical Hierarchy Process Model applied for different chosen criteria of watersheds that affects the sustainability can enable prioritization of different watersheds for stage wise improvement in the developmental strategies leading to sustainability of the area. The sustainability analysis of issues using different in the Integrated Mission for Sustainable Development (IMSD). Application of the ( IMSD)norms require integrated raster analysis using the reclassified run off potential layer, soil erosion raster layer and slope raster layers in raster GIS analysis. This will yield output layer giving details regarding the areas in the watersheds suitable for different conservation measures. The same is required to criteria associated with sustainability can derive be validated through field investigation for ascertaining the economies, increase in efficiencies of conservation measures, improved productivity, and above all good returns on investment (ROI).The details are described in the paper. reliability of the chosen sites. The issue regarding water availability must be considered for locating conservation measures and also care needs to be exercised in the form of suggesting hydrologic conservation sites away from built up localities. Keywords: Spatial Interpolation, AHP Modeling, Integrated Watershed Development, Composite Sustainability Index, Environmentally Sustainable Development, Soil and Water conservations, Soil and runoff estimation models. 1. INTRODUCTION The automated watershed delineation module in GIS software is a useful tool for delineation of watersheds in the area. The input for delineating watersheds in the module is a depression free Digital Elevation Models (DEM) created using raster local interpolation techniques in which depressions are removed by increasing the cell value to the lowest overflow point out of the sink. The D8 method used for watershed delineation is known to give good results in zone of convergent flows and along well defined valleys; it tends to produce flow in parallel lines along the principal direction. The DEM generated using contours of appropriate interval can facilitate creation of output products such as slope, slope length and other morphologic parameters of watersheds. The runoff potential obtained for different landscapes of the watersheds using Soil Conservation Services (SCS) run off model and watershed based soil erosion potential determined as a function of slope length using Stehlik s equation can be used in the raster analysis for creation of runoff and soil erosion potential raster layers. The raster layers of slope, runoff potential, and soil erosion potential The AHP analysis (Saaty, T.L.1977) can be utilized for the chosen watershed parameters that affect sustainability. The improvement in environmental sustainability associated with changes in the different chosen criteria involving sustainability can be considered in the AHP analysis. This can include improvement in productive land cover, reduction in degraded area, reduction in soil erosion potential, reduction in runoff due to construction of water conservation measures, and reduction of ruggedness number associated with construction. Temporal change in land cover type based on the suggested activities, and associated environmental impact require scientific deliberations to study the impact of landscapes changes, anthropogenic influence, and its further usability. The temporal changes in land cover for a given period can be studied using LISS-III remotes sensing data covering the area and by grouping the watershed area into two cover categories. The cover-1(c1) in the area can give an assessment regarding improvement in productive land cover and in the same manner the cover-2(c2) can be utilized to indicate reduction in degraded land during the period. The AHP analysis in the same manner is considered suitable to ascertain the reduction in the remaining three chosen watershed criteria during the temporal period. The AHP analysis involves assigning subjective weights ranging from one to nine based upon the extent of reduction or increase given to the chosen watershed criterias that improves environmental sustainability of the eight watershed area. Online Available at UNIETS-December

2 The AHP analysis (Saaty, T.L.1977) consists of assigning pair wise weights to the chosen criteria and to prepare pair wise comparison matrix and its corresponding normalized weights. Subsequently multi criteria weights are to be assigned to each of the chosen criteria depending upon the magnitude of the changes observed during the temporal period. Then the Sustainability Index (EI k ) is required to be computed for each criterion encompassing all the watersheds in the area using equation-1. (EI k ) = Σ(Weight obtained for the K th criteria in the J th Watershed area * Reduction/Increase of K th criteria for J th Watershed/(Area of J th Watershed ) (1) Where K is from 1 to n and J is from 1 to m The Composite Sustainability index (CSI) derived based upon the chosen criteria s gives a quantitative assessment about the environmental sustainability for different watersheds. This is a useful parameter for prioritizing the watersheds to carry out action plans for each watersheds leading to sustainable development. The CSI value will have relative contribution of each of the different chosen criteria and is obtained using equation-2. CSI = EI-1 *W1 + EI-2 *W2+ C3 EI-3 *W3+ EI-4 *W4+ EI-5 *W (2) W1, W2..W5 are the pair wise weights derived from the AHP discussed earlier for the five criteria chosen in the analysis and EI-1, EI-2 EI-5 are the sustainability index for the five criteria. A obtained CSI value ranging from to indicates a moderate to average sustainable development for the area, more the magnitude of CSI, higher would be the sustainability for the watershed area there by requiring lesser suggested measures for its sustainable development. This can alter the landscapes towards improved sustainability. The details are discussed in the succeding paragraphs. 2. STUDY AREA AND METHODOLOGY The study area lies in Ahmednagar District of Maharashtra including Tahsil Rahata, Shrirampur, and Newasa between to N and to E extents. The entire area falls in Pravara River Basin. The S.O.I toposheet for the area were digitized to obtained contour of 20 meter interval and raster tools were used to generate DEM. The GIS technique of Raster analysis was used to generate depression free Digital Elevation Models (DEM) created using raster local interpolation techniques in GIS terrain analysis environment. The depression free Digital Elevation model was the input product for automated sub basins delineation. The threshold value governs the size of the micro-watershed (Saptarshi & Rao 2010). Eight suitable sized watersheds were delineated in GIS watershed module using optimum threshold value activated using trial and error approach. The Soil Conservation Services Model (SCS) was used for each watershed to generate the runoff potential raster layer for the area. For this purpose LISS-III Remote sensing data was digitally classified to obtain level-i landscape details for the watershed using maximum likelihood algorithm and acquiring curve numbers for different landscapes. Slope and aspect layers were generated in raster domain and soil erosion for each watershed was quantified using the sthelik s equation through use of various input parameters such as slope-length, climatic factor, petrology factor, erosion factor of the soil and vegetation factor. Continuous raster layers for the area were created for slope, soil erosion, and runoff potential. The raster layers of slope, runoff, and soil erosion were reclassified as low, medium, and high categories to perform mathematical based raster integration using the raster calculator in the GIS environment. The output raster layer arrived after the raster integration process was analysed based on the criteria specified in IMSD for different soil/water conservation measures to locate suitable sites for various conservation measures. The conservation sites were verified on ground by conducting field inspections to ensure validation of the GIS suggested sites. Sites for hydrological conservation structures were located close to the streams to ensure water availability and the structures were placed away from built-up area to enable lesser environmental impact in the area due to interference of hydrological conservation measures. Table-I gives the criteria followed in site suitability analysis for different conservation measures Table-I: Criteria for Site suitability of conservation sites Sr. Type of Run off Slope Soil No Conservation Potential Erosion potential 1 Contour Bunding Medium Low High 2 Gully Plug High Mediu m Online Available at UNIETS-December Low 3 Stream bunds Medium Low Medium 4 Farm Pond High Low High The eight delineated watersheds showing the suggested conservation sites were evaluated using AHP modeling for a temporal period of five years (February 2008 to January2013) using Remote sensing LISS-III data as discussed to evolve composite sustainability index as a measure of environmental sustainability for the five chosen criteria. This can necessitate the actual requirement of suggested conservations that are required to be constructed to improve the sustainability of the area. Fig-1 gives the LISS-III image of eight watersheds and the details of suggested conservation measures for the watersheds.

3 The multi criteria approach utilized following five criteria for AHP analysis such as (a) Improvement in productive land covers (C-1). Table-II: Pair-wise assignment of AHP Criteria Weights for the five chosen criteria Criteria C1 C2 C3 C4 C5 C C C C C (b) (c) (d) Reduction in degraded area(c-2). Reduction in soil erosion potential (C-3). Reduction in runoff potential(c-4). (e) Reduction of ruggedness number (Morphologic Parameter) (C-5). 3. RESULTS AND DISCUSSIONS The pair wise AHP criteria matrix giving the subjective pair wise criteria weights depending upon the degree of correlation between the corresponding pair wise criteria is given in Table-II. In the Table-III the normalised AHP weights were computed and the products of two arrays consisting of pair wise comparison matrix as one array and column matrix of weights as another array were added to give the value of Xw. Each value in column Xw. was divided by the corresponding weights (w) and averaged, the average of Xw./w has been computed. The value of consistency index (CI) was calculated using equation-3. CI = {average Xw. /w n}/(n-1), where n = number of criteria (3) The consistency ratio (CR) was computed using equation-4 Fig-1: Study area and study area giving details of conservation measures The temporal remote sensing data was useful to study the level-1 landscape changes during the temporal period of study. CR=CI/RI, where RI=Random index which for n=5 is (4) Online Available at UNIETS-December

4 Table-III: Normalisation of AHP Weights and computation Cri t C-1 C- 2 of CR C-3 C-4 C-5 Wt (w) C C C C C The consistency ratio (CR) has been calculated using CR=CI/RI, where RI is the random index. The value of CI/RI is to be maintained less than 0.1 by altering the weights in the pair wise comparison matrix by assigning appropriate weights as given in Table-III. The multi-criteria weights for the temporal changes in respect of all the five criteria were assigned based upon the magnitude of changes and the multicriteria weights ranged from one to nine depending upon the magnitude of change.the details are given in Table-IV. After assigning the subjective weights for the different criteria in all the eight watersheds, the value of EI-K was computed in respect of all the chosen criteria for the eight watersheds using equation-1. The details of EI-K values are given in Table-V. The EI-K values are index arrived after multiplying the multi-criteria weights given in the against each criterion in the Table-IV and the corresponding changes in the criteria value per unit area of the watershed. The magnitude of EI-K values will give the extent of temporal changes that has taken place in the watershed over the chosen period. Higher values are indicative of more changes for the correspnding criteria within each watershed. X w X w./w CI C R= CI /R I Table-IV: MultiCriteria Parameters and Their corresponding Weights Watersh ed No with area of watershe ds shown in bracket in sq- KM) Cover- 1Area Increase (ha) And weight indicate d in Cover-2 Area Reductio n (ha) And weight indicated in Criteria C-3 Reductio n in Soil erosion potential (Kg/sqm/year) And weight indicated in 1.(205.5) 13(8) 20.10(7) 0.017(2) 2.(661.8) 11(6) 29.95(9) 0.063(6) ) 15(9) 22.50(7) 0.10(1) 4.(255.3) 14(8) 18.0(5) 0.09(9) 5.(312.9) 16(9) 30.05(9) 0.05(5) 6.(214.6) 3.0(2) 14.50(1) 0.03(3) 7.(240.5) 2.17(1) 18.30(5) 0.06(6) 8.(550.3) 2.34(2) 19.07(6) 0.03(3) Criteria C-4 Reduction In Runoff Potential, Runoff (cm)/rainfall.(c m) And weight indicated in Criteria C-5 Reduction In rugged ness number And weight indicated in. Ruggedness Number = Average Ruggedness of watershed terrain (in metres)* Drainage density (in Sqmetres/Sqm) (3) = (7) (3) = (2) (4) = (3 ) (3) = (4 ) (2) (4) (3) = (6) 0.37(4) = (5) 0.6(6) = (3) Online Available at UNIETS-December

5 Table-V: EIk Values for Different Criteria and For Eight Water shed No Watersheds EI-1 EI-2 EI-3 EI-4 EI E E E E E E E E E E E E E E E E E E E E E E E E E E-10 Table-VI: CSI-Index Values for Eight Watersheds Watershed No CSI- Values PRIORITY To Be ACCORDED FOR SUSTAINABLE DEVELOPMENT Average to Moderate Average Moderate Low Average to Moderate Moderate Average Very High The Composite Sustainability Index (CSI values) was computed using the EI-K values for the different criteria and the corresponding AHP weights for the respective criteria given in Table-III. The composite sustainability index values for the watersheds ranged from to Table-VI gives the CSI values for the watersheds along with the priority to be accorded for the watersheds to achieve sustainable development based upon the CSI value. The higher CSI values are indicative of more sustainable watershed development and consequently lesser priority is to be accorded for developing such watersheds. On the contrary a lesser value of CSI index indicates low sustainable development and accordingly more suggested conservation measures may have to be carried out on such watersheds having low CSI values on a higher priority to achieve environmentally sustainable development. 4. CONCLUSION The integrated watershed developmental programs are aimed at suggesting sites for conservation of water and soil using different models for the purpose. In this context the site suitability analysis for different watershed based conservation measures can be carried out using the different norms specified for each conservation means. The reliability of the suggested sites for sustainable development will however depend upon the productive changes that occur in the watersheds owing to the phase wise implementation of suggested conservation measures. In this context the Analytical Hierarchy Process Model based evaluation can be carried out for the watersheds of the study area by choosing a specified temporal period during which productive landscape changes are expected to occur and which can alter the watershed properties. The outcome of the AHP model studies applied over the specified temporal period can give an estimation of the Composite Sustainability Index (CSI) for each watershed. This index may be regarded as a measure to ascertain the extent of sustainable development that has taken place and also to prioritize the watersheds based upon the CSI values for further phase wise watershed development to meet the objective. 5. REFERENCES 1. Chaurasia R., Loshali D.C., Dhaliwal S.S., Minakshi Sharma P.K., Kudrat M. and Tiwari A.K (1996), ' Landuse change analysis for agricultural management - a case study of Tehsil Talwandi Sabo,Punjab'. Journal of Indian Society of Remote Sensing, Vol. 24, No.2.pp Online Available at UNIETS-December

6 2. Dabral. P.P. Chaudhary. V.M. Mal B.C. (2006) Estimation of runoff for agricultural watershed using SCS curve number and geographic information system. 3. Durbude DG, Purandara BK and Sharma A (2001) Estimation of surface runoff potential of a watershed in semi arid environment - A case study. J Indian Soc Remote Sens 29(1&2): Kumar, P., Tiwari, K.N. and Pal, D.K. (1997). Establishing SCS runoff curve number form IRS digital database. J. Indian society of remote sensing, Vol 19, No 4, pp Saaty,T.L.(1977). A Scaling method for priorities in Hierarchical structures,journal of Mathematical Pschology,15: Saptarshi P. G. and Rao K. R. (2010) Comparative assessment of micro-watershed silt load with morphological parameters to evaluate soil conservation strategies, Current Science vol. 98 no. (3). 7. Shreedhara V. and Balakrishnaiah M.H (2008). Integrated watershed development plan for Hirehalla watershed in Gadag District, Karnataka, using Remote Sensing and GIS approach SOUVENIR VOLUME Geological Society of India Pp Online Available at UNIETS-December