Design With Terrain and Gravels: Nature-Based Drainage Solutions for Sustainable Stormwater Management of Urban Areas

Research output: Book/ReportPh.D. thesisResearch

  • Alazar Assefa Wondim
Rapid urban growth and global climatic variability result in frequent flooding in urban areas and pose unprecedented stress on the existing drainage infrastructures. In developed nations, a shift in urban stormwater management from relying exclusively on gray, pipe-based drainage infrastructures towards green, nature-based approaches referred to as Sustainable Drainage Systems (SuDS), among others, is currently taking place. In cities of developing countries, the existing gray infrastructures are not well developed, prompting an opportunity of performing a technical leapfrogging towards SuDS. Through vigilant adoption of this increasingly-practiced nature-based drainagesolution,municipalities can provide better drainage and flood control and create a fertile ground for more co-benefits to local residents in terms of livelihood and livability.This Ph.D. thesis identifies options to improve the drainage challenge of settlements developed over higher slope terrains and low lying plains of urban areas in developing countries with the high rate of urban growth and drainage infrastructure deficit, through terrain modifications and introduction of gravel-based drainage design solutions as a nature-based drainage option to control flooding and provide co-benefits. The study is presented in three parts based on two empirical studies from case sites, both developed in the south-western fringe of Addis Ababa, Ethiopia, and one desktop study building upon one of the empirical studies. The case studies present the design of novel drainage and stormwater harvesting solutions constructed by using locally available materials and terrain modifications. The first design is for drainage of cobblestone streets in hilly areas. The design is referred to as Infiltration Bumper with Tree Planter (IBTP) and targets flood prevention, groundwater recharges and city greening simultaneously. The second design is for the management of stormwater in low lying residential areas. The design is referred to as Elevated Retention and Detention Basin (ERDB), and targets waterlogging prevention, stormwater harvesting, and green area improvements. The first solution (IBTP) is developed and tested to control stormwater runoff generated from the local cobblestone streets within the designated case study catchments for a 2-year storm event corresponding to 40 mm over 2 hours. The second solution (ERDB) is developed and tested to control 100% stormwater runoff generated from the Jemo condominium (the multistory residential neighborhood in Addis Ababa) within the designated case study catchments for the same storm event. The desktop-study resulted in a GIS-based planning tool for upscaling of the IBTP to a city-wide solution.The results of the study indicate that the design outputs are applicable to newly planned urban areas as well as retrofitting in already developed urban areas with similar land uses and geophysical situations. Moreover, by applying the nature-based drainage solution into a wider spatial scale, the systems ensure flood control with more co-benefits to human settlement frequently vulnerable to flooding and drought as compared to conventional methods. If considering the local context of cities in developing countries, the suggested designs can enhance the green infrastructure and contribute to the movement towards urban resilience. Future research should focus on implementation in municipal policies and guidelines, as well as full-scale pilots for refinement of the design. Citywide implementation of the solutions additionally calls for research on the institutional transition to support the technological transformation from relying only on gray to greener and sustainable drainage systems.
Original languageEnglish
PublisherInstitut for Geovidenskab og Naturforvaltning, Københavns Universitet
Number of pages102
Publication statusPublished - 2020

ID: 250548101