Evaluation and Optimization of Distributed Stormwater Controls in Spreadsheet

Maximizing on-site stormwater management is one of the key concepts of distributed stormwater controls, such as those used as a part of Low Impact Development (LID) and sustainable sites approaches. These approaches are usually expressed as (1) maximize on-site depression storage and infiltration, (2) minimize runoff discharge by minimizing directly connected impervious area (DCIA), (3) maximize flow paths and time of concentration, and (4) maximize the potential for evaporation and/or evapotranspiration (ET). A few process models are available to evaluate these types of distributed stormwater control alternatives directly. The purpose of this paper is to describe how to evaluate and optimize distributed urban stormwater control options in a spreadsheet environment. One methodology to evaluate stormwater control alternatives is to compare total runoff volume from long-term continuous simulation. Using a lumped simulation model, it can be difficult to adequately represent the physical characteristics of distributed onsite LID options. Another alternative evaluation and optimization method based on lot-level detailed functional spatial information and explicit rainfall-runoff estimation is presented in this paper.