Integrating Engineering and Social Aspects in Selecting Stormwater Control Measures (SCMs)

The Low Impact Development (LID) approach to stormwater management is rapidly becoming the required replacement for the traditional approach of development design, solely for peak runoff attenuation. Stormwater Control Measures (SCMs) used in LID designs are some combination of physical structures and /or agronomic practices designed to capture runoff, remove pollutants, promote groundwater recharge, and protect receiving streams from channel degradation. The LID approach has been studied and documented in many journals and design manuals, but we know of no comprehensive study that combines the engineering (hydrologic performance requirements) and social aspects (complementary requirements) of the approach. SCMs have historically been designed by engineers solely to meet performance requirements for runoff volume, peak runoff rate, and water quality impact, but engineering designs seldom take into account the equally critical complementary design requirements such as aesthetics, social impacts, and safety concerns. On the other hand, plans developed by landscape architects and other designers too often focus on complementary requirements—emphasizing aesthetic features, spaces for social activities, and creating sanctuary for wildlife–without adequately taking into account engineering hydrologic performance requirements. The lack of understanding in the relationship between the engineering and social aspects can result in inappropriate selection of the SCM, resulting in the ultimate failure of the design to achieve its goals. This study produced a flexible logical framework to reflect a wide range of possible complementary goals. The framework includes a detailed description of all necessary inputs for a complementary score, a definition of the flow of logic, logic rules used in the decision process, some description of inputs needed for the hydrologic calculations, and a rough cost estimate. The logical framework will allow the selection of the “best” SCM(s), defined as meeting the hydrologic performance requirements while yielding the highest possible score for site-specific complementary requirements. The tool is intended to be used at the early stage of design process to help designers —stormwater engineers and landscape architects—obtain initial estimates of dimensions of the possible SCMs suitable for the design.