The U.S. Environmental Protection Agency (EPA) recently posted results from Phase 5.3.2 of the Chesapeake Bay Community Watershed Model (the Phase 5.3.2 model), the most recent iteration in EPA's effort to quantify the watershed-wide inputs of Total Nitrogen, Total Phosphorus, and Total Suspended Solids to the Chesapeake Bay. As part of the calculation process for nutrient inputs from urban development, the model's estimate of pollutant loads from urban areas relies on an estimate of impervious surface area. The Phase 5.3.2 Model indicates that impervious surfaces are growing more slowly than population, at a ratio of 0.7:1 (rather than a 5:1 ratio as discussed below).
As discussed previously in Field Notes Volume 18, No. 4, Volume 18, No. 5, and Volume 18, No. 6, an erroneously-high rate of growth in impervious area (originally cited as being five times as high as population growth) had once been used as a rallying cry against urban/suburban development and the pollution it produces. The Chesapeake Bay Model, however, continues to show that impervious surfaces are growing more slowly than the population; the recently-released Phase 5.3.2 model indicates that, between 1985 and 2010, the ratio of impervious surface growth to population growth was 0.7 to 1 (see Table 1, below). |
This updated information is important because all parties must work together if we intend to Save the Bay, and the course of action must be dictated not by emotional arguments that reference inaccurate sound bites but instead by rational, data-based dialogue.
For more information on the Chesapeake Bay TMDL, please contact Mike Rolband, Jennifer Brophy-Price, or Bethany Bezak. |
