The interaction between surface and groundwater flows in alluvial riverbeds is subject of numerous researches in recent years due to the necessity of better understanding the physical processes involving mass and momentum exchange between both flows. Seepage exists if the material that constitutes any hydraulic structure or river bed is permeable enough and if there is a difference between the upstream water level and the tail water level downstream. Due to the fact that groundwater flow rates are much smaller than open-channel flow rates; seepage is commonly neglected by river engineers in the analysis of civil and environmental engineering problems. Nonetheless, this small groundwater flow can represent an important factor in many physical processes.