The City performs maintenance to streams and channels throughout the city to preserve their capacity to carry 100-year floodwaters, and for repairs to erosion damage, stream corridor degradation, stabilization/restoration. The increasing frequency of intense storm events requires increasing funding for sediment and vegetation removal to ensure the conveyance capacity of these waterways as climate resiliency and adaption measures consistent with the City’s Climate Emergency Declaration.
2021 Four Mile Run Channel Dredging Project -- More Information Coming Soon
The Four Mile Run Channel includes a federal flood control project. Periodic dredging of significant accumulated sediment in the channel that borders between the City of Alexandria and Arlington County is required to maintain conveyance capacity and free board for the channel. Evaluation for areas requiring dredging to re-establish the required freeboard was performed in Spring of 2018. The evaluation used the Re-Authorized flows which officially changed the “Authorized” design flow per the 2014 USACE Water Resource bill. Dredging is required to meet this requirement to mitigation against flooding loss for properties in the Four Mile Run watershed.
In an agreement entered on, and dated 26 March 1974 and 8 April 1974, respectfully, Arlington County and the City of Alexandria have a shared responsibility for maintenance of the Four Mile Run East and West Levee Systems to include the open channel of Four Mile Run - the north side being Arlington County’s responsibility and the south side being the City of Alexandria’s responsibility.
The Four Mile Run Sediment Removal Project will restore the required capacity to provide the free board set by USACE. Project work will be conducted in an environmentally sensitive area (in an RPA, FEMA Floodplain, Water of the U.S., and U.S. Army Corps of Engineers Flood Control Levee and Channel). Total Land Disturbance is 7.15 Acres. (311,517.5 SF). The shared maintenance of the open channel of Four Mile Run includes clearing of debris, vegetation growth, and shoaling as required by the USACE annual inspection program.
2014 Holmes Run & Cameron Run Stream Maintenance Project
The Department of Transportation & Environmental Services (T&ES) conducted routine stream maintenance work in Holmes Run and Cameron Run starting in early April 2014. This work will consist of removing woody vegetation in the immediate vicinity of bridge and culvert crossings, and selectively removing dead and downed trees throughout the runs. Efforts will initially focus on Holmes Run, and will transition to Cameron Run. Removing dead trees and woody vegetation near bridges and culverts is essential to public safety during floods. Dead and downed trees may be dislodged during flood flows and become stuck at the faces of bridges and culverts. Logs and other debris may create a dam, which may increase water-surface elevations and flood larger areas. Woody vegetation on the stream banks inhibits the efficient flow of water through channels and may also raise water-surface elevations and increase flooding. Generally, the work will consist of removal of all woody vegetation from bottom third of the stream banks. Clearing of all invasive species will occur for the rest of the stream bank. Healthy trees at the top of stream banks will not be removed. Some trees at the top of the bank will be limbed up where low limbs are near to walking/bike trails. The work will be performed by The Care of Trees, under the supervision of their ISA Certified Arborists.