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Landfill sites selection for municipal solid waste using multi criteria evaluation techniques. Case of Rusizi town, Rwanda

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par Fidele RUGIRAMANZI
National university of Rwanda - Post Graduate Diploma in Applied Geo-Information Science 2013
  

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4.3.1.1. Environmental criteria 4.3.1.1.1. Land slope

(Lin & Kao, 2005) have suggested that the appropriate slope for constructing a landfill is about 8-12% because too steep of a slope would make it difficult to construct and maintain while too flat of a slope would affect the runoff drainage. Slopes above 12% created high runoff rates for precipitation. With higher runoff rate and decreased infiltration, contaminants are able to travel greater distances from the containment area.

4.3.1.1.2. Proximity to wells and Forest

A landfill must not be located near any surface streams, lakes, rivers, wells, or wetlands. Proximity to wells was an important criterion to accessing the landfill site. Landfills create noxious gases and leachate that make them unsuitable to be in proximity to water wells (Dorhofer & Siebert, 1996). For this reason, a 300-m buffer would be placed using the function in GIS software, which will be used to generate the buffer around all wells and forests.

4.3.1.2. Social- economic criteria

4.3.1.2.1. Airports

Landfill sites attract variety of birds to be accumulated around. This issue may interfere with the operation of airplanes. So it is essential to consider suitable distance from landfill site according to airport and airplane types (Daneshvar, 2004). By considering this criterion as a constraint, for safety matters, 3 kilometer buffer around airport was omitted from the next investigation.

4.3.1.2.2. Roads network

Landfill location must be close to roads network in order to facilitate transportation and consequently to reduce relative costs. However, aesthetically and logically a buffer of 100 meter has been considered in this study. In other words, direct relationship between distance from roads and land suitability is started from the 100 meter distance of roads.

4.3.1.2.3. Schools, Hospitals and Markets

By considering this as a constraint, a buffer of 01 Km will be reserved to Primary and Secondary schools, health centers and District hospitals, and markets (REMA, 2010).

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4.3.2. Landfill site determination

The site selection analysis involves three steps: preliminary analysis, multi-criteria evaluation, and identification of the most suitable site. The preliminary analysis stage involves creating a study area map to input the data layers, then creating permissible area map for landfill sites in Rusizi town.

The second step involves performing GIS overlaying, which is conducted by combining the non restricted area map and slope analysis map in order to get the suitable landfill sites in Rusizi town that would be located in the intersection of non restricted area and suitable slope. The final step relates the finding of suitable sites using the information in advanced GIS and REMA regulations regarding landfill site's size.

Non restricted area map, Slope analysis map, Potential landfill sites in Rusizi town, Potential landfill sites in Mururu Sector, Potential landfill sites in Gihundwe Sector and General Suitability maps were created and produced.

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