Sediment modelling and design optimization for stormwater ponds

Stormwater ponds, including dry ponds, wet ponds and constructed wetlands, have been widely used for sediment removal from stormwater runoff. In this paper, sediment removal mechanisms, modelling approaches and optimization of design for stormwater ponds are reviewed and discussed. The settling velocity for discrete particles is introduced and compared. Settling velocity distribution should be characterized for individual sites for the most cost-effective design of new stormwater ponds. Different methods for estimating trap efficiency of stormwater ponds are then summarized, including empirical models and theoretical models. The sediment transport modelling method is also discussed. Optimization of pond design for improved sediment removal is described, with many key factors taken into account such as residence time, vegetation, wind, turbulence, stratification, inflow and outflow. A high system hydraulic efficiency can be achieved through proper design of the shape of the pond, length-to-width ratio, baffling, depth, and the location of inlets, outlets and vegetation. Finally, various issues associated with typical numerical models for sediment transport in stormwater ponds are discussed. This review paper intends to provide a state-of-the-art of sediment modelling in stormwater ponds and to point the direction for design optimizations.