Evaluating the hydraulic capacity of existing drain systems and the management challenges of stormwater in Addis Ababa, Ethiopia

• Published in: Journal of hydrology. Regional studies Vol. 25; p. 100626
• Main Authors: Adugna, Dagnachew, Lemma, Brook, Jensen, Marina Bergen, Gebrie, Geremew Sahilu
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-10-2019; Elsevier
• Subjects: Addis Ababa; Ethiopia; Flash flooding; Hydraulic capacity of drains; Integrated land-use planning; Stormwater runoff; Addis Ababa; Integrated land-use planning; Flash flooding; Ethiopia; Hydraulic capacity of drains; Stormwater runoff
• ISSN: 2214-5818; 2214-5818
• DOI: 10.1016/j.ejrh.2019.100626

•Waste dumping into drains were the major contributors of flash flooding by reducing the hydraulic capacity of drains.•Investing on drains alone is not a solution in urban areas, it should be integrated with waste management.•The stormwater discharge into each drains and their hydraulic capacity should be critically considered to evaluate the performance of drains.•The hydraulic capacity of drains should be designed based on hydraulic and hydrologic parameters.•Collaboration along stakeholders in urban areas is key to sustainable stormwater management.
Addis Ababa, Ethiopia.
Addis Ababa is undergoing rapid urbanization with unprecedented high rate of road and building constructions, resulting in a sudden upsurge of sealed surfaces and generation of significant amounts of stormwater. The present study therefore aims to investigate the hydraulic capacity of existing drains and stormwater management challenges using detailed field surveys, and stakeholders' interview. 469 road segments (74 km) and 202 drain segments (42.76 km) in two representative case sites confined in 564.54 ha boundary areas were physically surveyed.
Results showed that 14% of the drains in new city parts and 28% in old city parts were in conditions inadequate for removal of stormwater, resulting in flash flooding and infrastructure degradation in the associated watersheds. Further, although more than 72% of the surveyed drains were oversized, stormwater overtopping reoccur as a season-to-season problem, ascribed to illegal dumping of waste into drains, reducing their hydraulic capacity. The challenges of stormwater management were related to lack of city-wide drainage master plan, absence of hydrologic data considerations during designing drains, and weak enforcement on solid and liquid waste dumping into drains. The present study recommends that building practices that minimize surface sealing and critical hydrologic and hydraulic considerations during designing drains, and educating the local community and stakeholders regarding waste management.