Analytical Hydrological Model for the Planning and Design of Low-Impact Development Practices

The analytical probabilistic models are promising hydrological tools for urban stormwater management. These innovative and robust models were developed based on the derived probability distribution theory which enables the derivation of the probability distributions of runoff-event characteristics based on the probability distributions of rainfall-event characteristics and the rainfall-runoff transformation equations. Rainfall-event characteristics were widely assumed to follow exponential distributions. The purpose of this paper was to develop a new analytical probabilistic model to be used for the planning and design of emerging green stormwater management practices known as low-impact development practices. Both infiltration-excess and saturation-excess runoffs are considered in order to determine the probability distribution function of runoff-event volume. These models can be used as tools to estimate the percentage of runoff volume that is reduced or treated by the low-impact development practices (LIDs). When incorporating LIDs, the impervious areas serviced by LIDs may be modeled as pervious areas which may generate saturation-excess runoff when the LIDs’ storages are filled. Because of their mathematical closed form, the analytical probabilistic models are easy to apply and capable of providing accurate estimates. Therefore, they can be used as an alternative tool for the planning and design of low-impact development practices.