Evaluating the Hydrologic Benefits of a Bioswale in Brunswick County, North Carolina (NC), USA

Abstract

Bioswales are a promising stormwater control measure (SCM) for roadway runoff management, but few studies have assessed performance on a field scale. A bioswale is a vegetated channel with underlying engineered media and a perforated underdrain to promote improved hydrologic and water quality treatment. A bioswale with a rip-rap lined forebay was constructed along state highway NC 211 in Bolivia, North Carolina, USA, and monitored for 12 months. Thirty-seven of the 39 monitored rain events exfiltrated into underlying soils, resulting in no appreciable overflow or underdrain volume. The bioswale completely exfiltrated a storm event of 86.1 mm. The one event to have underdrain-only flow was 4.8 mm. The largest and third-largest rainfall depth events (82.6 and 146 mm, respectively) had a large percentage (85%) of volume exfiltrated, but also had appreciable overflow and underdrain volumes exiting the bioswale, resulting in no peak flow mitigation. Overall, this bioswale design was able to capture and manage storms larger than the design storm (38 mm), showing the positive hydrologic performance that can be achieved by this bioswale. The high treatment capabilities were likely due to the high infiltration rate of the media and the underlying soil, longer forebay underlain with media, gravel detention layer with an underdrain, and shallow slope.

Descriptive Analysis of the Performance of a Vegetated Swale through Long-Term Hydrological Monitoring: A Case Study from Coventry, UK

“…The authors distinguished between those variables affecting the drainage area, such as the discharge area, the discharge ratio and the main concentration at the swale inlet; those variables associated with the swale itself, such as the swale length, slope, type of soil, vegetation and operational life. This research also revealed the limitations of previous work, emphasizing the need for continuous and long-term monitoring alongside later work such as Purvis et al [12]. Most of the investigations carried out in the literature show a limited number of storm events which introduces a certain level of uncertainty, as they miss the major hydrological effects influenced by the climate on the location, the rainfall and temperature patterns and the seasonality.…”

“…This study represents one of the largest studies presenting data from three complete hydrological years and 19 storm events captured for detailed analysis during the 6 months stage where on-site weather data were available. Therefore, resulting in a longer period than other significant studies recently published such as those by Leroy et al [34], Purvis et al [12], Lisenbee et al [29] and Andrés-Valeri et al [33], amongst others.…”

“…Therefore, the hydrology should also reach this threshold in order to be reliable and representative for comparison with other international studies. Recent research, such as Purvis et al [12], monitored 39 storm events over 12 months in a bio-swale in North Carolina, USA, which also followed the described conditions.…”

Decision-Support System for LID Footprint Planning and Urban Runoff Mitigation in the Lower Rio Grande Valley of South Texas

“…The DSS predicted the most promising results from the BS in terms of land use utilization to meet 10-year frequency targeted discharge (0.12 m 3 /s), with the peak outflow rate of 0.113 m 3 /s and a smaller footprint (0.72 ha) than other types. The BS structure is often designed for better conveyance, collection, and infiltration of stormwater runoff [60]. The structure is highly vegetated with grass throughout its length and sloped sides to improve the surface runoff and infiltration, which was also encountered in our modeled bioswale.…”

Detailed Quantification of the Reduction Effect of Roof Runoff by Low Impact Development Practices

“…The reduction effect of roof runoff by LID practices and their combination need to be evaluated in detail to test their effectiveness and support LID selection, planning and decision making. The hydrological effect of most individual LID practices at the building scale has been fully studied by many previous experimental and observational studies [6,8,[15][16][17]. Many models have been used to simulate the effect of individual LID practices, and some of these models can perfectly reproduce the hydrological performance of actual LID [18][19][20].…”