ASSESSMENT OF IMPACT OF POOR URBAN DRAINAGE SYSTEM ON ROADS IN FLOOD PRONE AREAS IN ADAMA CITY

Urban areas, particularly in developing countries, are often plagued by poor drainage systems, leading to frequent flooding and disruption of transportation. This research focused on Adama City, a flood-prone area in Ethiopia, and investigated the impact of its urban drainage system on roads. Despite being among the largest urban infrastructures urban drainage systems do not always function flawlessly. Failures in urban drainage system occur regularly in practice, resulting in malfunctioning systems, and high costs. To anticipate their malfunctioning, and thus to improve their performance, a better understanding of failures occurring in urban drainage system and their underlying causes was needed. Using a mixed-methods approach, the study employed questionnaires, site visits and semi-structured interviews with urban professionals, engineers and authorities. This study presented an inventory of causes of poor urban drainage system, an analysis of their root causes and their impact on roads then recommending mitigation strategies. For identification of flood prone areas GIS-based hydrological modeling, quantitative analysis, and qualitative surveys were implemented. This research implemented both probability and non-probability sampling techniques; thus, purposive sampling and random sampling were used to decide locations to be studied and passengers to be asked respectively. Both primary and secondary data collection methods were implemented in order to acquire the appropriate data. The results showed that the interfaces between drainages and other urban systems are prominent failure locations. In addition, the study found that failures originate from the entire development process of urban drainage system, i.e., from the design, construction and user/maintenance phase. With respect to the causes underlying these failures, the results showed that these are mainly socio-institutional in nature. The study also concluded road blockage by waste and surface flood, reduced load bearing and roadside surface erosion as the major impacts of poor drainage on roads. The study at the end set out list of mitigating strategies for the identified root causes and for the impacts that poor drainage causes on roads.