Analysis of Sewer Chokes Using GIS: A Case Study Nairobi City Western Region

Abstract

Nairobi city has been facing sanitation problems related to sewage outflows and sewage pipe bursts. Nairobi City Water and Sewerage Company (NCWSC), a state owned water utility, uses Operation and Maintenance Information System (OMIS) in sewer chokes analysis in order to reduce the number of chokes occurring within their jurisdiction. This study focused on spatial sewer choke analysis in Nairobi's Western Region using Geographic Information Systems (GIS) which would enable easier spatial understanding of the chokes as well as improve on visual interpretation of otherwise complicated and detailed raw data. Data on causes of chokes was collected through field surveys and interviews and the frequency of these causes determined. Hot spot analysis on the data spatially revealed the hot and cold spots in the region. GIS was found to be useful as it spatially reflected the relationship and strength of each factor to choke formation. Further, Geographic Weighted Regression (GWR) was used to spatially reveal the trends offactors that influence choke occurrences. High population density, poverty level, number of households, vandalism and water supply were the major factors that contributed to high choke volumes in the region