A City Bounded by Rivers
A landscape architectural framework for mitigating water pollution and supporting ecological restoration along the Mbagathi and Kandisi Rivers
J.D. Veenstra (TU Delft - Architecture and the Built Environment)
N.M.J.D. Tillie – Mentor (TU Delft - Architecture and the Built Environment)
Kristel Aalbers – Mentor (TU Delft - Architecture and the Built Environment)
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Abstract
Rapid urbanisation in Ongata Rongai, Kenya, has transformed the Mbagathi and
Kandisi Rivers from ecological corridors within a wider hydrological system into
degraded rivers affected by urban and peri-urban activities. Weak sanitation,
drainage and waste systems have contributed to the discharge of sewage,
stormwater runoff, solid waste, agricultural pollution and wastewater from local
activities into the river system. At the same time, the degradation of riparian
zones, forested source areas and native vegetation has reduced the landscape’s
capacity to absorb, filter and buffer polluted flows.
This thesis explores how a landscape architectural framework can enable local
stakeholders to mitigate water pollution and support ecological restoration along
these rivers. Through a research-by-design approach, the project combines spatial
analysis, literature review, stakeholder conversations and design exploration. The
research frames river pollution as a spatial, ecological and governance-related
problem, caused not only by contaminated flows, but also by the loss of ecosystem
services that once supported natural water regulation and purification.
The outcome is a framework consisting of two interrelated parts: an ecological
framework at the catchment scale and a water quality framework at the urban
scale. Together, they identify where landscapes should be restored, reconnected
or protected, where polluted flows should be prevented, intercepted or treated,
and which spatial strategies are suitable for different locations. Local design
explorations then show how this framework can be translated into more specific
interventions.
The thesis concludes that improving river water quality depends on rebuilding the
ecological capacity of the catchment while addressing specific pollution pathways
in the urban landscape. For implementation to succeed, local stakeholder interests
and economic benefits must be central, especially where formal governance and
enforcement are limited