ABSTRACT
Buffer strips are frequently suggested as a means to protect environmentally sensitive areas from nonpoint source loadings. At present, decisions on buffer widths are often based on minimum separation distances regulatory agencies specify between a sensitive area and the upland area generating the loadings. However, computer models do exist, and are able to simulate the pollutant-trapping efficiency of buffer strips. These models have the potential to assist decision makers in selecting optimum buffer widths for specific settings.
In this study, the CREAMS model was used to assess the effectiveness of buffers in protecting a wetland located downslope from an adjacent proposed urban development site. Data sets were prepared describing both existing site conditions and midconstruction conditions. Buffer strip widths were identified which the model predicted would bring sediment loading rates during the midconstruction periods down to levels matching the loading rates associated with the existing site conditions. The modeling exercise highlighted the importance of ensuring that runoff from the upstream area enters the buffer strip as uniform sheet flow to maximize buffer strip efficiency. The modeling also proved valuable in identifying points where sediment control techniques other than buffering were needed to fully protect the wetland from excess sediment loading as a consequence of urban construction activities.
