BUILDING A HYDROLOGICAL AND HYDRODYNAMIC MODEL WHILE FACING CHALLENGES IN DATA AVAILABILITY IN THE OSHANA REGION OF CENTRAL NORTHERN NAMIBIA

摘要

In recent years, heavy floods occurred in the Oshana region in central northern Namibia. These floods affected the Town of Oshakati as well, the capital of the Oshana Region. Namibian authorities approved the funding for all studies and works necessary to make Oshakati flooding free, so the town can further develop as foreseen in the Concept Master Plan. For this, a 22 km long dike and diversion channel will be constructed, to divert the main flows conveyed by the oshanas, the ephemeral rivers characterizing the region. After public tendering BAR was selected to lead the full project, from conceptual design to supervision of the works. Within the project, IMDC performed the hydrological and hydrodynamic study. The main challenge for this study was the scarcity of data: due to logistical challenges, flow and water level measurements were rare. However, satellite imagery from the 2011 flood event do was available, and the hydrodynamic and hydrological models were concurrently calibrated by comparing simulated flood maps with the satellite imagery. The lack of data had its impact on the accuracy of the results, but model results were suitable enough to deliver vital input to the design process and to assess the hydraulic impact of the works.