Control of Residential Stormwater by Natural Buffer Strips

ABSTRACT

This field study evaluated the effectiveness of natural buffer strips to remove phosphorus and suspended solids from residential stormwater. Four experimental sites and one control site were selected for uniformity of vegetation and parent soil material, with slope being the prime variable. The selected slopes fell into two groups: (1) 1–5% slope; and (2) 10–15% slope. All sites were at least 46 m (150 feet) in length and tested at 8 m (25 ft) intervals so that buffer strip effectiveness could be examined as a function of length. Each experimental buffer strip received elevated inputs of phosphorus and sediment from either a subdivision or a condominium complex. A unique system of in-ground sampling cups was used to collect runoff samples throughout the plots. It was concluded that residential runoff is relatively high in phosphorus and suspended solids, especially during the construction phase of residential developments. The effectiveness of natural buffer strips is highly variable, but in most cases, a 15 m (50 ft) natural buffer was effective in reducing phosphorus concentrations to background values observed at the control site. Ground cover had a more significant impact on pollutant removal than slope. Some areas of exposed soil actually contributed suspended solids to the overland flow. It is anticipated that the results of this study will help guide regulators in properly sizing buffer strips in residential subdivisions. It is recommended that site inspection be incorporated into the sizing process, given the high variability of buffer strip quality between sites.

Key Words:

• nonpoint pollution
• phosphorus
• filter strips
• buffer strips
• suspended solids
• residential stormwater