Storm Water Drainage Systems’ Effectiveness and Adequacy in Managing Storm Water Discharge in Kisii Municipality, Kenya

  • James Okinyi Manyara Meja Department of Environment, Natural Resources Management and aquatic sciences, Kisii University, P.O Box 408-40200, Kisii, Kenya
  • Getabu Albert Department of Environment, Natural Resources Management and aquatic sciences, Kisii University, P.O Box 408-40200, Kisii, Kenya
  • Onchieku James Department of Environment, Natural Resources Management and aquatic sciences, Kisii University, P.O Box 408-40200, Kisii, Kenya
  • Ogendi George Department of Environment, Natural Resources Management and aquatic sciences, Kisii University, P.O Box 408-40200, Kisii, Kenya
  • Okwadha George Department of Civil and Construction Engineering, Technical University of Kenya, P.O Box 52420-00200, Nairobi, Kenya
Keywords: Flash floods, Storm Water Management, Storm Water Management Model

Abstract

Urbanization and increased developments have put pressure on important infrastructure like storm water drainage networks, often resulting to flash floods and blockage of drainage structures. This study assessed the effectiveness and adequacy of storm water drainage systems (channels) in Kisii municipality, in collecting and discharging storm water. The study areas for drainage networks were selected purposively based on the drainages type (concrete, earth and grass lined). Discharge was calculated based on the amount of rainfall, duration of rain, land use and slope of the study area. Land use maps and drainage network were generated in Personal Computer Storm Water Management Model (PCSWMM) using satellite maps and digital elevation models respectively. The effectiveness was established by routing runoff water in the PCSWMM. Surcharged culverts and joints indicated inefficient storm water drainage systems, resulting to ponding and flooding. Results from this study indicated that there were instabilities in conduits and surcharge in nodes. Surcharging of nodes was experienced for up to 22 hours at Daraja Mbili while ponding in Mwembe lasted for up to 22 hours. The level of surcharge and flooding on Rivers was experienced within 15 minutes of a rainfall in Nyanchwa sub catchment.

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Published
2021-09-07
Section
Articles