Detention ponds improve the water quality of drainage water before entering free-surface waters. Ponds design depends on the geomorphologic conditions and composition of drainage systems. Hydraulic and treatment efficiency are negatively influenced by hydraulic problems such as dead space and short-circuiting. In the framework of this study, a detention pond located in the State of Brandenburg, Germany is optimized with respect to its hydraulics based on vertically-averaged 2D numerical flow and transport simulations with the modelling system TELEMAC 2D. Sensitivity studies of dominant parameters and processes were carried out. Inlet design and flood conditions showed an influence on hydrodynamics and transport processes. The impact of baffles, their lengths, and number has been investigated. Four baffles of 70% of pond width provided the best hydraulic and removal efficiency.