Stormwater Management Ecological Metrics in Urban Design

As part of the New Orleans Urban Water Plan, Dana Brown & Associates created a report known as the Ecological Services Metrics that addressed the existing hydrologic conditions of four water management districts including the East Bank of Orleans Parish west of the Industrial Canal, New Orleans East, East Bank of Jefferson Parish, and St. Bernard Parish and determined the measurable results of green infrastructure for each district. Understanding the measurable results at a district level was critical to communicating the need for strategies that are different from traditional approaches to water drainage and to compare benefits to costs for an understanding of return on investment at a site scale.Pilot project areas were chosen after analyzing typical land cover and urban growth patterns categorized into 10 unique typologies. Each typology was also analyzed to determine the most appropriate water management strategies that could be implemented on both public and private land at differing levels of intervention. In addition to new development, existing areas would undergo retrofitting of green infrastructure through the use of corner basins, wet ponds located on vacant lots, porous pavement, and urban bioswales. The interventions were distributed throughout neighborhoods and urban typologies to demonstrate how they could be implemented incrementally without requiring large scale system upgrades. The results of the report showed that runoff within the first flush, or first one inch of rainfall, could be substantially reduced preventing back-flooding and pump failure. Other benefits associated with the green infrastructure that were quantified within the report include increased groundwater infiltration, reduced soil subsidence, improved water quality, decreased heat island effect, and improved air quality.