The Intricacies of a Watershed Plan – Modeling, Planning & Restoration

In 2002, the Columbus City Council approved a moratorium that effectively prohibited development requiring the extension of City-owned sewer and water into the Franklin County portion of the Big Darby Creek watershed. Franklin County imposed a similar ban for unincorporated areas with the watershed. The action was in response to concerns that changing the face of the land within the watershed would cause a degradation that begins with excessive pollutant loading to stream channels and leads to a loss of aquatic habitat and other wildlife.A comprehensive study of the subject watershed was launched to assess current environmental conditions, as well as modeling impacts associated with future land use changes. The assessment of current conditions included an environmental sensitivity analysis to identify portions of the planning area that should be preserved to prevent the most profound impacts to the ecosystem. The assessment was aided by a GIS-based mapping and data compilation effort that supported a base land use plan. The modeling process used to predict the impacts within the planning area caused by future land use changes was based on actual measurements of precipitation (rainfall), stream flow and the amounts of certain pollutants conveyed in the stream system. The modeling identified unique combinations of land cover and soil types. For lands in agricultural use (the majority of the planning area), the model provided a very detailed representation of crop type, rotation, fertilizer/herbicide application and final yield. EMH&T was able to successfully adapt the agricultural-oriented model to mimic a variety of future urbanized land uses within the planning area. To consider the implementation of stormwater best management practices (BMP) in conjunction with future land uses, a separate BMP analysis tool was utilized and demonstrated a preferred approach to reduce the stormwater impacts associated with development. In support of this analysis, EMH&T provided guidance on comprehensive policies for stormwater management and watercourse protection.EMH&T provided a thorough ecosystem evaluation of the area. Engineers and environmental scientists worked directly with data collected in the planning area regarding existing aquatic (e.g. fish, reptiles, mussels, insects, etc.) habitat. As part of the modeling and related evaluation tasks, EMH&T worked with EDAW to identify those measures that would protect and conserve the fragile ecosystem. Stream restoration and wetlands preservation opportunities and methods were identified. Collaboration also occurred to identify preferred methods for low-impact development and stormwater BMP applications.The final product is a recommendation for the use of each acre of the planning area to minimize the pollutants impacting the main waterways. The recommendations protect highly sensitive areas and include designations of open space throughout the planning area. Varying densities of residential and non-residential development are located where they can best be served by the existing and planned infrastructure. Success is determined by the continued thriving of a vibrant aquatic ecosystem. The health of that ecosystem is the indicator for the health of the environment and the people who depend on it.