Table 1.
Factors hypothesized to influence community having low sanitation coverage in Amhara Region, Ethiopia, 2011–2014
| Variable | Hypothesized influence on sanitation coverage | Reason | Data and source | Variable creation |
|---|---|---|---|---|
| USDA soil texture classes | HWSD, v.1.2.24 Includes a 30 arc-second GIS raster image linked to an attribute database with characteristics of topsoil (0–30 cm) and subsoil (30–100 cm) | Observed topsoil texture classes within the study area included clay, clay loam, loam, and sandy clay loam. Indicators were created for each, excluding sandy clay loam as referent | ||
| Clay | Positive | More stable soil | ||
| Clay loam | Positive | More stable soil | ||
| Loam | Positive or negative | More or less stable soil | ||
| Sandy clay loam | ||||
| High soil gravel content | Negative | Soils with higher gravel content are less stable | HWSD, v.1.2.24 Includes a 30 arc-second GIS raster image linked to an attribute database with characteristics of topsoil (0–30 cm) and subsoil (30–100 cm) | Observed topsoil volume percentage gravel (materials > 2 mm) within study area included values of 1 and 29, 31, and 32. To create an indicator of higher gravel content, 1 was coded as 0, and 29, 31, 32 were coded as 1 |
| Surface form | Positive or negative | Specific land forms may capture other mechanisms determining latrine pit collapse | U.S. Geological Survey Africa Ecosystems Mapping project26 | Indicators were created for each of seven land surface form observed within study area, excluding high mountains/deep canyons as referent |
| Low-lying land | Negative | Low-lying areas have higher moisture potential may be more likely to flood | U.S. Geological Survey Africa Ecosystems Mapping project26 | Indicator created for low-lying land, based on two classes of topographic position (uplands and lowlands/depressions) |
| Altitude | Positive or negative | Altitude may capture other mechanisms determining latrine pit collapse | NASA Shuttle Radar Topographic Mission digital elevation data processed by the Consortium for Spatial Information of the Consultative Group for International Agricultural Research28 | Altitude divided by 100 |
| Percent slope | Negative | Greater slope may increase soil instability | Same as altitude | Calculated in ArcMap 10.1 |
| Annual average NDVI 2011 | Positive or negative | Higher vegetation may increase availability of materials for latrine construction or decrease demand for sanitation by providing areas for open defecation | Africa Soil Information Service MODIS collection: vegetation indices, April 2014 release, Center for International Earth Science Information Network, Columbia University29 | NDVI multiplied by 10 |
| Total annual rainfall | Negative | Higher annual rainfall results in flooding or damage to latrines | Interpolated surfaces with mean monthly precipitation (mm) from 1950 to 200030 (available at: http://www.worldclim.org; accessed January 20, 2015) | Surfaces were added in ArcGIS 10.1 to get total annual rainfall. Total annual rainfall (mm) divided by 100 |
| Population density 2011 | Positive | Higher population density may increase demand for sanitation by reducing areas for open defecation and need for privacy | Oak Ridge National Laboratory's LandScan32 | Population density log10 transformed |
| Distance to roads | Negative | Greater distance to roads may decrease demand for sanitation as it reflects lower perceived need. Lower access to roads reflects lower exposure to new ideas and markets and lack of mobility | Global Roads Open Access dataset31 | Shapefile with paved, gravel, or dirt/sand roads used to create raster surface for Amhara Region indicating distance in kilometers to a road in ArcGIS 10.1 |
GIS = geographic information system; HWSD = Harmonized World Soil Database; NDVI = Normalized Difference Vegetation Index; USDA = U.S. Department of Agriculture.