Development of a flood warning system for the lower Rufiji flood plain, Tanzania

The study describes both hydrological modeling and hydraulic routing designed basically to simulate floods along the Rufiji River in Tanzania. The Hydrological modeling is carried out for the upper catchment covering Great Ruaha, Kilombero and Luwegu Rivers, then down to Rufiji at Stiegler's Gorge and to Mloka due to the complex nature of the Tagalala region. The daily discharge values from Luwegu River are estimated by choosing a subcatchment that has a similar mean annual rainfall (MAP) value to that of Luwegu, and assuming that the runoff generation mechanism from the chosen catchment is the same as that of Luwegu catchment, except for the difference in their areas. The method was found to be better than the commonly adopted method of subtracting directly, the flow from Kilombero (at Swero), and Great Ruaha (at Kidatu), from the Rufiji River at Stiegler's Gorge, which does not consider the routing effects. The hydraulic routing considers flood wave propagation models based on the Finite difference methods, which apply an implicit scheme for dynamic wave to solve the Saint Venant equations. Finally a flood warning system is presented that gives the travel time of any given flood at various locations downstream of the river and the extent of flooding in case the river bursts its banks