Citation

Juma B, Olang LO, Hassan MA, Chasia S, Mulligan J, Shiundu PM. Phys. Chem. Earth (Pt A B,C) 2023; 132.

Copyright

(Copyright © 2023, Elsevier Publishing)

DOI

10.1016/j.pce.2023.103499

PMID

unavailable

Abstract

Overlapping conditions of rapid urbanisation and climate change across developing countries are threatening the capacity of cities to manage climate risks, especially in the flood-exposed low-income peripheral areas. Limited studies have applied hydrodynamic flood models in ascertaining flooding conditions, supportive of risk-informed decisions in such urban fringes. Against this backdrop, we assessed plausible flooding and hazard conditions in the low-lying villages of Lindi and Silanga in Kibera informal settlement. The coupled one-dimensional and two-dimensional hydrodynamic model, customised from the Hydrological Engineering Centre's River Analysis System (HEC-RAS) was parameterised for flood simulation under different hydrological regimes and scenarios associated with flooding in Kibera. Volumetric flow estimates and a computed energy slope were used to define the upstream and downstream modelling boundary conditions respectively. Trial-and-error adjustment of the flow resistance coefficients from land-use features was applied in model calibration, and the results compared to the surveyed flood of 23rd April 2019.

RESULTS show that proximal areas to the Ngong River and Nairobi dam face high flood risks. A flood volume of 11.7×105m3 from a 2.5h, 50 mm rainfall could potentially inundate about 2.0% and 8.3% of areas in Lindi and Silanga respectively, while a volume of 48.9×105m3 from a 100-year storm of 172 mm could inundate about 10.6% of Lindi and 29.1% of Silanga. Upstream steeply sloping topographies of the villages increase flood velocities and risk of drowning, while the lower reaches at relatively flatter topographies, experience attenuated flow and rapid accumulation of flood waters, hence, higher flood depths. These results can support policy interventions for integrated flood risk management in Kibera, as a way of mainstreaming the underserved urban communities in climate risk management.

Language: en

Keywords

Flood hazard assessment; Flood risk management; HEC-RAS model; Hydrodynamic flood modelling; Kibera settlement; Urban fringes