Developments in LIDRA 2.0: A Planning Level Assessment of the Cost-Effectiveness of Low Impact Development

This paper describes the ongoing development of Low-Impact-Development Rapid Assessment Model (LIDRA), a planning level model for assessing the cost-effectiveness of low impact development (LID) as a means of reducing runoff and runoff-related problems in urban watersheds. The newest version, LIDRA 2.0 is an open-source web-based application. LIDRA 2.0 generates stochastic precipitation ensembles nonparametrically from local historical data sets using a markov chain and bootstrapping method. Precipitation is applied to watersheds with parcel and surface distributions and geometries specified by the user and stored in a SQL server database. LID scenarios and associated adoption/repaving rates are then used to perform multiple 30-year simulations, during which the difference in runoff (compared to the baseline, no-LID scenario) is calculated using a water balance that invokes the Thornthwaite Mather approach for pervious parcels. A life-cycle cost analysis computes the net present value of the LID program implementation (based on user-specified adoption/repaving rates), separating out the capital and O&M costs. The model contains a built-in database of the LID system performance and cost values drawn from national data sets. In this paper, we demonstrate the newest features of the model with a Bronx, NY case study.