The Pearl Mill Branch of South Ellerbe Creek is fed by two major systems of pipes: one drains most of downtown Durham through Central Park, while the other drains Duke East Campus and Trinity Park. During the 1900s, this system was gradually built to carry water rapidly from the many roofs, roads, and streets directly to the creek. The large volumes of water rushing through South Ellerbe at the Pearl Mill Preserve after every big rain have, over time, eroded the banks and deepened the creek to the point where it also acts like one of these large stormwater pipes. Because of how deep it is, the creek can’t flood except in really extreme rain events. So, over time, people have been lulled into developing in the floodplain. Too many people in the floodplain means there’s even greater pressure to stop the stream from flooding. Problem is, streams need to flood on occasion to stay healthy and clean.
So how can we help get out of this cycle of stream destruction?
ECWA has partnered with the City of Durham, Duke Energy, and the City of Raleigh Watershed Protection Program to install a series of bioretention cells along Rand Street, just east of the creek, this winter. A bioretention, much like a rain garden, is a shallow depression that captures stormwater and infiltrates it into the ground. Underneath the plants and mulch, a bioretention contains several layers of sand and gravel. This filters pollutants and nutrients out of stormwater run-off before it flows into a pipe and slowly flows to the creek as clean water.
And that’s not all that ECWA is doing to help heal the creek at Pearl Mill.
In 2018, ECWA purchased the nearby Soles Property with support from the City of Raleigh Watershed Protection Program and a Durham Open Space and Trails Matching Grant. The Strayhorn Branch, which flows into South Ellerbe just north of Green Street, has also eroded down more than three feet! ECWA is in the planning stages of a project to heal Strayhorn Branch. This project will help reinforce the banks, restore a natural riffle-and-pool structure, and reintroduce Strayhorn Branch to its former flood plain in the adjacent woods.
This combination of Creek Smart® projects will make Pearl Mill more inviting to visitors while helping to heal South Ellerbe Creek. Upon completion, these two projects will serve as stops on ECWA’s Creek Smart® tour (www.creeksmart.org) to educate our community and encourage visitors to use similar nature-based solutions to manage stormwater in their own yards, businesses, and neighborhoods.
The Pearl Mill Bioretentions will serve as a filter to clean runoff before it enters the creek.