Retrofitting LID Practices into Existing Neighborhoods: Is It Worth It?

Timothy J. Wright, Yaoze Liu, Natalie J. Carroll, Laurent M. Ahiablame, Bernard A. Engel

Low-impact development (LID) practices are gaining popularity as an approach to manage stormwater close to the source. LID practices reduce infrastructure requirements and help maintain hydrologic processes similar to predevelopment conditions. Studies have shown LID practices to be effective in reducing runoff and improving water quality. However, little has been done to aid decision makers in selecting the most effective practices for their needs and budgets. The long-term hydrologic impact assessment LID model was applied to four neighborhoods in Lafayette, Indiana using readily available data sources to compare LID practices by analyzing runoff volumes, implementation cost, and the approximate period needed to achieve payback on the investment. Depending on the LID practice and adoption level, 10-70 % reductions in runoff volumes could be achieved. The cost per cubic meter of runoff reduction was highly variable depending on the LID practice and the land use to which it was applied, ranging from around $3 to almost $600. In some cases the savings from reduced runoff volumes paid back the LID practice cost with interest in less than 3 years, while in other cases it was not possible to generate a payback. Decision makers need this information to establish realistic goals and make informed decisions regarding LID practices before moving into detailed designs, thereby saving time and resources.