Conceptual Morphologic Consideration for Long-term Hydrodynamics Simulation in the Pirai River in Santa Cruz-Bolivia

Abstract:

Santa Cruz city is built along the Piraí River, part of the Amazonas basin, which has tremendous discharge variability from10 to almost 2000 m³/s. The width goes from 50 to 500 metres.

Inflows were calculated and calibrated using a conceptual rainfall-runoff model in hourly time step for 14 years. A hydrodynamic model (Mike11) of the river is implemented and calibrated with two stations. It was found that the roughness coefficient decreases with increasing water level; therefore bed resistance equation in function of the velocity were calibrated for different historical events. The last part of the river has important morphological process during flood events, conceptual modification of the wet area and the hydraulic radio (in different cross sections) is proposed in order to estimate in a better way the water level changes. Even when the model (Mike11) is running with fixed bed, the water levels are well represented. The shape and the time of occurrence of the peak flow in outlet station were well represented with EF greater than 0,7.