Estimation of soil loss through water erosion is an essential exercise which can help decision makers and planners determine the severity of soil loss through rill and sheet erosion and also curtail the development of further gullies in an area already ravaged by gully erosion. While Universal Soil Loss Equation (USLE) is the most commonly adopted model because it provides a straight forward approach for qualitative estimation of soil loss, however its rainfall erosivity component is found incompetent in most parts of the world. To overcome this deficiency, the Revised Universal Soil Loss Equation (RUSLE) was implemented using rainfall erosivity (R) values peculiar to tropical environment of the Anambra area of Nigeria. Rainfall erosivity (R-factor), soil erodibility (K-factor), slope factor (LS-factor), and cover management (C-factor) were generated in GIS environment and then integrated based on RUSLE equation to estimate the rate of soil erosion. The study indicated that about 1804.39 km 2 (39.49 %) of the study area have slight erosion rate of 0-10 t ha-1 year-1 , while the rates of erosion in 746.60 km 2

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Groundwater potential characterization is a major component of the developmental strategies required for sustainable management of the water resources of a country. This study explores the potential of Natural Resources Conservation Service (NRCS-CN) estimated runoff/infiltration to verify a knowledge-based groundwater potential zone mapping methodology using remote sensing and GIS. Eight criteria/factors regarded as positive indicators to the existence of groundwater in the study area were mapped and weighted based on the knowledge of the local geology using analytical hierarchy process (AHP). The results from AHP were integrated using Weighted Index Overlay Analysis in a GIS environment to delineate the groundwater potential map of the area. Five classes consisting of very good, good, moderate, fair and poor groundwater potentials, each occupying 4.6, 53.3, 82.22, 37.47, and 0.43 km 2 , respectively, were delineated. They were found to be in agreement with the borehole information of the area. Curve number (CN) for the various land cover types was generated using the NRCS-CN approach. CN was used to compute a qualitative, terrain-based, runoff/infiltration response for rainfall events in the study area, from which a terrain-based runoff map of the area was computed. A comparison between the groundwater potential map and terrain-based runoff map was done using linear regression analysis. The coefficient of determination (R 2) obtained was 0.80. The result indicates a high application efficiency of NRCS-CN method in verifying the accuracy of a GIS-based qualitative groundwater potential mapping.

A major challenge in most growing urban areas of developing countries, without a pre-existing land use plan is the sustainable and efficient management of solid wastes. Siting a landfill is a complicated task because of several environmental regulations. This challenge gives birth to the need to develop efficient strategies for the selection of proper waste disposal sites in accordance with all existing environmental regulations. This paper presents a knowledge-based multi-criteria decision analysis using GIS for the selection of suitable landfill site in Ado-Ekiti, Nigeria. In order to identify suitable sites for landfill, seven factors -land use/cover, geology, river, soil, slope, lineament and roads -were taken into consideration. Each factor was classified and ranked based on prior knowledge about the area and existing guidelines. Weights for each factor were determined through pair-wise comparison using Saaty's 9 point scale and AHP. The integration of factors according to their weights using weighted index overlay analysis revealed that 39.23 km 2 within the area was suitable to site a landfill. The resulting suitable area was classified as high suitability covering 6.47 km 2 (16.49%), moderate suitability 25.48 km 2 (64.95%) and low suitability 7.28 km 2 (18.56%) based on their overall weights.Key words: landfill, GIS, AHP, environmental management, spatial planning IzvlečekPomembna naloga v mnogih hitro rastočih mestnih naselbinah v deželah v razvoju, ki nimajo izdelanega plana rabe prostora, je zagotoviti trajnostno in učinko-vito ravnanje s trdnimi odpadki. Izbira lokacije ni lahka spričo zapletene okoljske zakonodaje. Odtod izvira potreba po izdelavi učinkovitih scenarijev izbiranja primernih odlagališč v skladu z vso obstoječo okoljsko regulativo. V tem članku poročamo o na znanju utemeljeni mnogokriterijski analizi, opravljeni v povezavi z geografskim informacijskim sistemom (GIS) za izbiro primerne lokacije odlagališča v nigerijskem mestu Ado--Ekiti. Pri izbiri so upoštevali sedem faktorjev -uporabnost, geološko sestavo, rečno mrežo, vrsto tal, nagib zemljišča, razpokanost kamnine in cestno omrežje. Vsak faktor so razdelili na razrede in ga rangirali glede na poprejšnje poznavanje ozemlja in obstoječe smernice. Posameznim faktorjem so pripisovali uteži s po-parnim primerjanjem ob uporabi Saatyjeve 9 stopenjske lestvice in hierarhične analizne metode (AHP). Z integracijo faktorjev glede na njihove uteži ob uporabi utežne indeksne analize podatkovnih slojev so ugotovili, da je 39,23 km 2 preiskovane površine primerno za lociranje odlagališča. Na tej površini so opredelili z ozirom na vse faktorje za zelo primerno 6,47 km 2 (16,49 %), zmerno primerno 25,48 km 2 (64,95 %) in malo primerno 7,28 km 2 (18,56 %) zemljišča.Ključne besede: odlagališče odpadkov, geografski informacijski sistem, hierarična analizna metoda, okoljska analiza, prostorsko načrtovanje

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