Mapping drought risk and community resilience: An integrated study of drought propagation, risk and adaptation strategies in the Horn of Africa

Agro-pastoral communities in the Horn of Africa (HoA) rely heavily on rain-fed agriculture and livestock herding, with over 95% of cultivated land dependent on rainfall. This makes production systems extremely vulnerable to climate variability and prolonged dry spells. Recurrent droughts disrupt food security, water access, and livelihoods, highlighting the urgency of proactive adaptation and resilience-building. Drought risk, however, is not determined by climate alone. It emerges from the interplay of environmental conditions, socio-economic vulnerabilities, and institutional responses. Limited access to nutrition, water, and sanitation, coupled with poverty and gender disparities, magnifies impacts, while targeted interventions and adaptive capacity help reduce them. Understanding how droughts propagate through the hydrological cycle and result in societal impacts is essential for effective management. This thesis investigates the multi-scalar dynamics of drought risk in the HoA, examining links between drought hazards, propagation processes, and societal impacts, while accounting for spatial variability and vulnerability. By combining biophysical analyses with socio-economic dimensions, it identifies drivers of drought risk and informs more effective, impact-based preparedness and management. Chapter 2 characterizes meteorological, soil moisture, and hydrological droughts across 318 catchments using standardized drought hazard indices (SPI, SSMI, SSI) and duration metrics. Spearman correlations and catchment characteristics (climate, soil, vegetation, geology, land use), reveal strong spatial variability. Wet, high-elevation croplands experience faster transitions, while semi-arid shrublands show prolonged persistence, especially in soil moisture and hydrological droughts. These results stress the need for region-specific forecasting that accounts for land cover and storage dynamics. Chapter 3 links drought hazards to societal impacts in Kenya’s arid and semi-arid lands. Using Spearman correlations and Random Forest (RF) regression modelling, the study finds that short-term precipitation deficits (2–6 months) increase water trekking distances, while milk production and malnutrition respond to medium-to-longer-term indices (5–24 months). Clustering counties by vulnerability factors (aridity, poverty, food security, water and sanitation access, gender disparities) improves model performance. Socio-economic clusters explain water access impacts best, while environmental clusters are more effective for agricultural and nutrition-related outcomes. Chapter 4 extends the framework to probabilistic risk assessment. RF-based drought impact hindcasts (1984–2014) estimate Average Annual Loss (AAL) and Probable Maximum Loss (PML). Results show spatial variability: northwestern counties face chronically high AAL for household water access, while eastern and southeastern counties experience high AAL for livestock trekking, milk production, and malnutrition. Findings highlight sanitation, water access, and poverty reduction as key adaptation entry points, with infrastructure such as small-scale water systems offering effective solutions. Chapter 5 evaluates the prolonged 2020–2023 drought compared with 2016–2018 in Kenya, Somalia, and Ethiopia. Survey data, impact analysis, and agent-based modelling reveal that while hazard intensity was similar, the 2020–2023 drought had more severe impacts, whereas 2016–2018 displayed greater regional variability. Simulations show that scaling up adaptation strategies (extension services, water harvesting, livelihood diversification), can reduce impacts but may create trade-offs, such as reduced downstream water availability. Overall, the dissertation demonstrates that drought risk in the HoA is shaped not only by climatic extremes but also by entrenched vulnerabilities. By advancing impact-based assessment, integrating probabilistic modelling, and emphasizing vulnerability-informed adaptation, the study highlights pathways toward risk-informed, spatially targeted interventions, long-term resilience, and stronger early warning and policy responses.