Mathare River Corridor Field Mission

The URESA-LAB methodology adopts an interdisciplinary, field-oriented approach to analyze informal settlements exposed to environmental risks, particularly floods in riverine areas. This methodology rests on the belief that informal settlements constitute dynamic socio-spatial systems, within which urban form, environmental processes, and human activities interact continually. Rather than relying solely on secondary data or large-scale models, URESA-LAB prioritizes direct field engagement to grasp context-specific conditions at a fine spatial scale.

Field observation and spatial analysis

Systematic field observation is a central element of the methodology. On-site visits document the morphology of settlements, construction typologies, circulation patterns, and the relationships between homes, banks, and drainage infrastructures. Particular attention is given to the interface between built structures and hydraulic networks, including culverts, open channels, riverbeds, and retention areas.

Visual documentation, through photographs and sketches, helps identify spatial configurations, material conditions, and obstruction points affecting water flow and flood propagation. This qualitative reading highlights how informal construction practices adapt to environmental constraints, while showing how spatial organization contributes to both vulnerability and resilience. It also enables identifying fine-scale elements, such as waste accumulation zones and informal drainage networks, often absent from official maps.

Environmental assessment and risk identification

The methodology integrates basic environmental assessment techniques to identify factors contributing to flood risk. This includes observing fluvial morphology, sedimentation, water level marks, and signs of erosion along the banks. The presence and condition of drainage infrastructures are evaluated, with particular attention to obstructions caused by solid waste and to the reduction of hydraulic capacity in culverts and channels.

Flood risk is approached as a space-embedded phenomenon, shaped by natural processes and human activity. Rather than producing numerical flood models, the URESA-LAB approach prioritizes qualitative and spatial indicators of risk that can be directly observed in the field. These indicators provide information on recurrent flood mechanisms and the cumulative impact of small-scale obstructions on water movement.

On-site observation of the river corridor

Field observations reveal that the Mathare river corridor is heavily degraded and under intense environmental pressure. About 70% of the corridor currently serves as an informal landfill, with more than 15 major waste accumulation sites identified along the banks.

Waste dumping into the river is continuous and systematic. Residents regularly throw their household waste directly into the river, and this practice extends to organized activities. Even during cleanup operations led by actors such as the National Youth Service, the collected waste is frequently dumped into the river, evidencing the lack of an effective waste management system.

The banks are also widely used as informal sanitation sites. Due to the lack of nearby sanitary facilities, open defecation occurs daily along the river. In some cases, existing sanitation facilities discharge effluents directly into the river, reinforcing the direct link between sanitation infrastructure and water pollution.

Waste accumulation areas are not only disposal sites but also informal economic activity spaces. Materials such as plastic, paper and organic waste are sorted and reused, thus fitting into small local enterprises. Livestock, notably cattle, goats and pigs, have been observed feeding within these waste deposits, highlighting the integration of waste into daily subsistence systems.

The vegetation along the river corridor is extremely limited, with fewer than 15 trees recorded, indicating a lack of ecological buffer zone and reduced environmental resilience.

Territorial conflicts and plurality of uses

The field study also identified zones of intense spatial conflicts, where several incompatible activities coexist in a very confined space. In some areas along the river, informal market activities, children's play areas, public toilets discharging directly into the river, illegal production of alcohol, and garbage dumps were observed simultaneously.

This overlap of functions creates extremely vulnerable environments, especially for children and other exposed groups. It illustrates the lack of land use planning regulations and highlights how river corridors become contested and multifunctional spaces in a context of scarcity.

Infrastructure deficits and environmental impact

The combination of survey data and field observations confirms that waste management is a key driver of flood risk. More than 20% of residents throw their waste directly into rivers or sewers, and more than 64% of respondents believe that waste accumulation contributes to flooding.

Furthermore, 71.9% of respondents report sewage overflows, indicating the limited capacity of sanitation networks. The river indeed serves as a final discharge point for solid and liquid waste, reducing its ability to drain stormwater and increasing the risk of overflow during rainfall.

Social consequences and service disruptions

Flooding has significant impacts on daily life. The survey results show that floods disrupt essential services, including water supply (78%), mobility (77.8%), sanitation (58.9%) and education (58.3%). Nearly half of households report income loss due to floods, and a significant number also report property damage and temporary displacement.

Access to water is already limited, most residents report irregular supply, and the situation worsens during floods. Additionally, about 29% of households report waterborne diseases, including diarrhea, malaria and cholera, highlighting the direct link between environmental conditions and health risks.

Qualitative interviews and institutional perspectives

The qualitative part of the study includes interviews conducted between April 12 and 15 with a diverse group of stakeholders, including local leaders, youth organizations, representatives of institutions, and professionals. These interviews included local leaders of Mathare Saint and Mathare Youth Talent, a candidate for Mlango Kubwa municipal elections, representatives of the University of Nairobi and the Ministry of Lands and Physical Planning, a field coordinator of the National Youth Service, leaders of local community initiatives such as Ujuane youth group, Heart Park and Miami Park, representatives of civil society organizations such as Face of Girls, and additional interviews with local actors.

These interviews highlight fragmentation of institutional responsibilities, insufficient coordination between official authorities and local actors, the lack of effective infrastructure systems, particularly in waste and sanitation, and the lack of preventive strategies with reliance on reactive measures. They also emphasize the importance of community initiatives and local engagement in managing daily environmental challenges.

The combined analysis of quantitative data, field observations and qualitative interviews shows that flood risk in Mathare results from closely related environmental, spatial and socio-institutional factors.

Summary

The river corridor functions as a multifunctional system, serving as a drainage canal, a waste disposal site, a sanitation space and an area of informal economic activity. These overlapping uses reflect the lack of infrastructure and spatial regulation, but also the adaptation strategies implemented by residents facing limited resources.

The quantitative survey confirms generalized exposure to floods, the frequency of floods and the significant impact of waste accumulation and the insufficiency of drainage systems.

Diagnostic

The diagnosis highlights three major structural problems: infrastructure failure, spatial vulnerability and governance gaps. The inadequacy of drainage, sanitation and waste management systems leads to ongoing environmental degradation. Housing near the river, on slopes or in low-lying areas increases exposure to flood risk. The lack of coordination between institutions and the absence of effective service delivery limit risk mitigation.

In this context, the river becomes the last receptacle for waste and wastewater, which greatly reduces its capacity to manage stormwater flows.

Main conclusions

Floods in Mathare constitute a structural problem, not just a natural phenomenon. Waste accumulation and obstruction of canals are major flood risk factors. The river corridor is a highly contested space, characterized by multiple incompatible uses. Sanitation gaps directly contribute to environmental and health risks. Residents are highly vulnerable, but also have local capacity for action.

Overall, the results show that flood risk results from the interaction of daily practices, spatial conditions and infrastructural constraints. To address it, integrated strategies at multiple scales and community-focused methods must be implemented.