Analytical Equations for Use in the Planning of Infiltration Facilities

This paper applies an analytical probabilistic approach to examine the hydrologic operations of nonvegetated infiltration facilities. Two sets of analytical equations for estimating infiltration facilities’ stormwater capture efficiencies and overflow frequencies are derived, one applying the Horton infiltration model and the other considering infiltration rates as constant. The acceptability of all the adopted simplifying assumptions is verified by comparing analytical results with continuous simulation results. Using Concord, New Hampshire, as an example location and infiltration trenches as an example type of infiltration facilities, the influences of underlying soil types, area ratios, and infiltration trench dimensions on their performance statistics are investigated. Both the Horton infiltration model and constant infiltration rates are shown to be acceptable for the tested location. The closed-form analytical equations can be applied as an alternative to continuous simulations for the planning of infiltration facilities.