Reservoir storage for managing floods in urban areas: a case study of Dzorwulu basin in Accra

Abstract

The study simulated the effect of using reservoir storage for reducing flood peaks and volumes in urban areas with the Dzorwulu basin in Accra, Ghana as case study. A triangulated irregular network surface of the floodplain was created using ArcGIS from ESRI by integrating digital elevation model and the map of the study area. The weighted curve number for the basin was obtained from the land use and soil type shape files using ArcGIS. The Soil Conservation Service curve number unit hydrograph procedure was used to obtain an inflow hydrograph based on the highest rainfall recorded in recent history (3–4 June 1995) in the study area and then routed through an existing reservoir to assess the impact of the reservoir on potential flood peak attenuation. The results from the analysis indicate that a total of 13.09 × 106 m3 of flood water was generated during this 10‐h rainstorm, inundating a total area of 6.89 km2 with a depth of 4.95 m at the deepest section of the basin stream. The routing results showed that the reservoir has capacity to store 34.52% of the flood hydrograph leading to 45% reduction in flood peak and subsequently 38.5% reduction in flood inundation depth downstream of the reservoir. From results of the study, the reservoir storage concept looks promising for urban flood management in Ghana, especially in communities that are over‐urbanized downstream but have some space upstream for creating the storage. Copyright © 2012 John Wiley & Sons, Ltd.

Flood hydrograph reconstruction from the peak flow value in ephemeral streams using a simplified robust single‐parameter model

“…Models dealing with the prediction or reconstruction of flood hydrographs are common, among them palaeo-flood hydrology and rainfall-run-off process simulation and flood routing (El-Hames and Richards, 1998;Sharma and Murthy, 1998;Greenbaum et al, 2001;Morin et al, 2001Morin et al, , 2009Costelloe et al, 2003;Milewski et al, 2009;Capart, 2013;Owusu et al, 2013;Greenbaum et al, 2014). With palaeo-flood hydrology, the main issue is reconstruction of the envelope curve for peak discharge.…”

“…With palaeo-flood hydrology, the main issue is reconstruction of the envelope curve for peak discharge. This information can serve as input for an assessment of flow volume (Jacoby et al, 2008), transmission losses (Greenbaum et al, 2001) or hazards (El Bastawesy et al, 2009;Owusu et al, 2013). In the field of rainfall-run-off modelling, the focus is often on flood hydrograph prediction.…”

Integration Techniques for Environmental Impact Assessment of Industrial Pollutants

“…Models dealing with the prediction or reconstruction of flood hydrographs are common, among them rainfall-runoff process simulation and flood routing [7][8][9][10][11][12][13][14][15][16][17]. In the field of rainfall-runoff modelling, the focus is often on flood hydrograph prediction.…”

Floodplain Mapping in Response to Surface Mine Reclamation

“…HEC-RAS was used to model reservoir storage, assess different types of river morphological data, assess a potential dam breach, develop a new method for real-time flood management in riverreservoir systems, demonstrate a 1-D jokulhlaup simulation, determine flood frequency, quantify hydrogeomorphic processes that influence alluvial gully erosion along a fluvial megafan, and compute water levels in a channel network (Owusu et al 2013, Saleh et al 2013, Yochum et al 2008, Malekmohammadi et al 2010, Alho and Aaltonen 2008, Maingi and Marsh 2002, Shellberg et al 2013, Knebl et al 2005 . From the case studies, it is shown that when channel cross-sectional data is unavailable, cross-sections can be created from high resolution DEMs (Knebl et al 2005, Yochum et al 2008, Owusu et al 2013, Shellberg et al 2013. Owusu et al (2013) completed a case study in the Dzorwulu basin in Accra, Ghana simulating the incorporation of reservoir storage to analyze the effects on the reduction of flood peaks and volume in urban areas.…”

“…From the case studies, it is shown that when channel cross-sectional data is unavailable, cross-sections can be created from high resolution DEMs (Knebl et al 2005, Yochum et al 2008, Owusu et al 2013, Shellberg et al 2013. Owusu et al (2013) completed a case study in the Dzorwulu basin in Accra, Ghana simulating the incorporation of reservoir storage to analyze the effects on the reduction of flood peaks and volume in urban areas. Longitudinal and cross-sectional channel characteristics were determined from a field survey, and combined with a TIN model to establish surface elevations.…”