Green-Grey Infrastructure Development for Sustainable Stormwater Management in Addis Ababa, Ethiopia
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Date
2026-05
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Addis Ababa University
Abstract
Rapid urbanization and climate change intensify stormwater challenges in developing cities. Conventional grey systems fail under extreme events, and green infrastructure alone is insufficient on steep slopes and poorly draining Vertisol soils. This dissertation develops an Integrated Green-Grey Infrastructure (IGGI) framework for Addis Ababa, Ethiopia, through four interlinked studies.
First, a GIS-based Multi-Criteria Decision Analysis (AHP and ANP) maps IGGI suitability across the city. The ANP model (AUC = 0.92, RMSE = 0.12) outperforms AHP, identifying 59.86% of Addis Ababa as suitable for IGGI. Second, PCSWMM modeling of a 30-ha steep, Vertisol-dominated micro-watershed shows that under climate change (SSP5-8.5, mid-term) peak flows increase up to 83%, while urbanization (80% imperviousness) raises pollutant loads by 7–12%. Urbanization is the dominant driver of water quality decline. Third, a TOPSIS-AHP-PCSWMM evaluation of 30 stormwater infrastructure units reveals that 42.3% are ready for GI retrofitting, with sediment accumulation and conveyance capacity as key performance determinants. Fourth, a novel IGGI system integrating buried rain barrels with conventional rain gardens is field-tested in a steep, Vertisol-dominated contributing zone. The system achieves 43.5% peak-flow reduction, 36.7% runoff-volume reduction, and 37.2–42.4% pollutant-load reduction – substantially outperforming conventional systems.
The findings provide a scalable, climate-resilient, and context-sensitive IGGI framework for Addis Ababa and comparable Global South cities, contributing directly to SDGs 6 (Clean Water and Sanitation), 11 (Sustainable Cities and Communities), and 13 (Climate Action).
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IGGI, stormwater management, AHP, ANP, TOPSIS, PCSWMM, runoff, pollutant load, climate change, Addis Ababa