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Flood Mitigation Assessment Using a 2D-model: In the Rwandex-Magerwa Catchment, Kigali, Rwanda

Sipulskis Travell, Juozas LU and Dahlström, Hannes LU (2025) In TVVR 5000 VVRM05 20251
Division of Water Resources Engineering
Abstract
In this research, 2D hydraulic modelling is applied in the Rwandex-Magerwa catchment to investigate the flood conditions and to quantify needed detention volumes during extreme rainfall. In the calibration uncertainties concerning calibration data were discovered, the total precipitation and outlet flow volumes show large differences, the difference in time between flow and rain peaks intensities vary and there were notable gaps in the data series. This should cause caution in the result interpretation.

Despite data uncertainties, the results are valuable in method development and give approximates of required storage capacities to achieve a flow below the maximum of the culverts’ outlet capacity for 2- to 100-year design storms are... (More)
In this research, 2D hydraulic modelling is applied in the Rwandex-Magerwa catchment to investigate the flood conditions and to quantify needed detention volumes during extreme rainfall. In the calibration uncertainties concerning calibration data were discovered, the total precipitation and outlet flow volumes show large differences, the difference in time between flow and rain peaks intensities vary and there were notable gaps in the data series. This should cause caution in the result interpretation.

Despite data uncertainties, the results are valuable in method development and give approximates of required storage capacities to achieve a flow below the maximum of the culverts’ outlet capacity for 2- to 100-year design storms are presented for conditions of 2020 and projected conditions of 2050. The main results show that the catchment outlet culvert capacity is exceeded already at a rainfall with a return period of 2 years, that flow bypasses the constructed channels and culverts and instead overflow KN3 road adjacent to the outlet and that a wetland storage provides a maximum capacity of 84 000 m3. On its own, sufficient to reduce the flow below maximum culvert capacity for rainfalls with a return period of up to 25 years. (Less)
Popular Abstract (Swedish)
I denna studie undersöktes översvämningsrisker i ett område i Rwandas huvudstad Kigali genom mätningar, observationer och modellering av ytvatten i programvaran HEC-RAS. De huvudsakliga resultaten från studien visade att mycket av den mätdata som samlades in från myndigheter i Kigali var undermåliga för kalibrering av en hydraulisk modell. Bland annat stämde ofta inte flödestoppar i regn och flödesmätningar överens och det fanns stora luckor i mätserierna.

Trots detta kunde resultaten från modellen, mätningarna och observationerna ge viktig insyn i de hydrauliska förutsättningarna i området. Studien visade att flödet i utloppet överstiger kapaciteten redan vid regn som statistiskt återkommer vartannat år. Vid sådana tillfällen räcker... (More)
I denna studie undersöktes översvämningsrisker i ett område i Rwandas huvudstad Kigali genom mätningar, observationer och modellering av ytvatten i programvaran HEC-RAS. De huvudsakliga resultaten från studien visade att mycket av den mätdata som samlades in från myndigheter i Kigali var undermåliga för kalibrering av en hydraulisk modell. Bland annat stämde ofta inte flödestoppar i regn och flödesmätningar överens och det fanns stora luckor i mätserierna.

Trots detta kunde resultaten från modellen, mätningarna och observationerna ge viktig insyn i de hydrauliska förutsättningarna i området. Studien visade att flödet i utloppet överstiger kapaciteten redan vid regn som statistiskt återkommer vartannat år. Vid sådana tillfällen räcker inte de byggda kanalerna och trummorna till, utan vattnet svämmar i stället över närliggande infrastruktur.

Studien pekar också på att en våtmark i området kan fungera som ett naturligt magasin med en kapacitet på cirka 84 000 kubikmeter vilket skulle kunna hålla flödena under utloppets kapacitet för återkomsttider upp till 25 år. Studien bidrar även med metodutveckling för studier gällande hydrauliska modeller i områden med begränsad dataåtkomst och kan vara vägledande i planeringen av framtida studier. (Less)
Please use this url to cite or link to this publication:
author
Sipulskis Travell, Juozas LU and Dahlström, Hannes LU
supervisor
organization
course
VVRM05 20251
year
type
H2 - Master's Degree (Two Years)
subject
keywords
hydraulic modelling, flood mitigation, HEC-RAS
publication/series
TVVR 5000
report number
TVVR-25/5015
ISSN
1101-9824
language
English
additional info
Examiner: Magnus Persson
id
9213795
date added to LUP
2025-12-08 14:16:21
date last changed
2025-12-08 14:16:21
@misc{9213795,
  abstract     = {{In this research, 2D hydraulic modelling is applied in the Rwandex-Magerwa catchment to investigate the flood conditions and to quantify needed detention volumes during extreme rainfall. In the calibration uncertainties concerning calibration data were discovered, the total precipitation and outlet flow volumes show large differences, the difference in time between flow and rain peaks intensities vary and there were notable gaps in the data series. This should cause caution in the result interpretation.

Despite data uncertainties, the results are valuable in method development and give approximates of required storage capacities to achieve a flow below the maximum of the culverts’ outlet capacity for 2- to 100-year design storms are presented for conditions of 2020 and projected conditions of 2050. The main results show that the catchment outlet culvert capacity is exceeded already at a rainfall with a return period of 2 years, that flow bypasses the constructed channels and culverts and instead overflow KN3 road adjacent to the outlet and that a wetland storage provides a maximum capacity of 84 000 m3. On its own, sufficient to reduce the flow below maximum culvert capacity for rainfalls with a return period of up to 25 years.}},
  author       = {{Sipulskis Travell, Juozas and Dahlström, Hannes}},
  issn         = {{1101-9824}},
  language     = {{eng}},
  note         = {{Student Paper}},
  series       = {{TVVR 5000}},
  title        = {{Flood Mitigation Assessment Using a 2D-model: In the Rwandex-Magerwa Catchment, Kigali, Rwanda}},
  year         = {{2025}},
}