Lower Booker Creek Watershed Study
The Booker Creek watershed covers a relatively large area in the Town of Chapel Hill’s jurisdiction, extending from the north to the eastern area of the Town’s limits. Except for a comparatively small area in the headwaters, the watershed is highly developed, and Lower Booker Creek, the subwatershed focused on in this project, is on the NC 303d Impaired Water Bodies list. It is also subject to problematic flooding during larger rain events. Biohabitats, a project team member, performed the following tasks for the study.
Engineering Field Investigation and Stream Walk–all intermittent and perennial streams in the subwatershed were assessed for geomorphic stability, stream channel characteristics, riparian buffer condition, aquatic habitat quality and buffer/stream restoration opportunities. In addition, outfalls to the stream channel 12 inches or greater were documented and described. All data was georeferenced in GIS.
Pre-survey Desktop Screening–A GIS analysis of residential street right-of-way (ROW) characteristics was used to determine potential green infrastructure retrofit opportunities before doing the field survey, to increase the survey’s efficiency. Green infrastructure opportunities were located using an array of factors such as road width, ROW width, slope, catch basin locations and tree canopy coverage.
Outfall Analysis–outfalls 18 inches and larger were analyzed in GIS using multiple factors to assess retrofit suitability. Engineering concepts were developed for the higher ranking sites.
Impervious Area Analysis–Impervious areas larger than one-half acre were identified in GIS which were feasible candidates for stormwater treatment retrofits.
Water Quality Modeling–Existing conditions were modeled in the watershed and then modeled again with proposed stormwater retrofits, to estimate water quality benefits of candidate retrofits.
Public Outreach–Biohabitats participated in several public information meetings to present project findings and answer stakeholder questions.
The project team provided the Town of Chapel Hill with a multi-faceted plan for improving water quality in the Lower Booker Creek watershed, which could potentially provide enough ecological uplift to remove Booker Creek from the 303d list.