Environmental Health Challenges of Open Drainage Systems in Onitsha, Anambra State, South East Nigeria

Open drainage systems in densely populated urban areas generate significant environmental health risks, including vector breeding, flooding, water contamination, and creation of malodorous and aesthetically objectionable conditions. This study assessed environmental health challenges associated with open drainage systems in Onitsha, Anambra State, South East Nigeria. Field assessments were conducted along twelve major drainage channels using a structured observation checklist. Water samples from drainage channels were analyzed for fecal coliforms, biological oxygen demand, and heavy metals. A cross-sectional survey gathered health data and perceptions from 360 residents in four wards adjacent to major drains. Results revealed that all twelve drainage channels assessed were partially or fully blocked with solid waste. Biological oxygen demand values in all sampled drains exceeded 300 mg/L, indicating severe organic pollution. Mosquito larval densities were significantly elevated in blocked drain sections. Fecal coliform counts in drain water adjacent to residential areas averaged 24,000 CFU/100mL. Sixty-six percent of surveyed residents reported experiencing flooding in their neighborhood within the past year, and forty-four percent attributed illness episodes to drainage conditions. Children were reported to play near drains in seventy-three percent of households, increasing contact risk. The study recommends urgent rehabilitation of drainage infrastructure, community drain-clearing campaigns, and improved solid waste collection to prevent drain blockage in Onitsha. Keywords: open drainage, urban flooding, Onitsha, vector breeding, environmental health.