Discharge Formulas for Subsurface Drainage of Retention Pond

Abstract

Excessive runoff and its undesirable effects (erosion, siltation, and suspended load), as well as water quality degradation in agricultural landscapes, are recurrent concerns in France. Special sediment control or pollution mitigation basins can consist of agricultural fields simultaneously ponded and subsurface drained. After having identified convenient nondimensional parameters for system description, two hydraulic methods for flow modeling and empiric design formulas are presented in this technical note for the evaluation of adequate water filtration flow rates through such remediation devices, under given hydraulic head conditions. The first method is an analytical one with an infinite soil domain and the second is a numerical one limited to the vicinity of the ponded zone. For engineering purposes, discharge capacity is given as a function of the number of drains as well as drain spacing, radius, and depth.