By Wyatt Shields
On Labor Day Weekend of 2018 and on July 8, 2019, the City experienced torrential downpours that caused widespread flooding and damage to many homes and businesses. These were two notable floods in a year of exceptional rainfall. Rainfall intensity exceeding 1 inch per 20 minutes will cause flooding in the City, and historically, this level of rain intensity is very rare. However, we are seeing an increase in frequency: in 2011, 2018, and 2019, the City experienced these “once in a 100 year” type of rain falls.
Immediately after the July 8 floods, the City and residents worked together to recover. The City waived fees for debris removal and building permits associated with flood repairs. Like many homeowners, the City also undertook repairs to damaged property, such as the Tripps Run channel and Oak Street Bridge. After the immediate recovery, we shifted to planning on how to reduce the severity and frequency of flooding in the future. Staff from the City’s Department of Public Works met with many homeowners who experienced flooding and hosted a town hall in August to hear directly from those impacted.
Where improvements are relatively simple and inexpensive, we are working to carry out solutions this year. Where solutions will require planning and engineering to determine the most cost effective solution, we will need to work together to prioritize how your Stormwater Fee dollars are best spent.
To that end, the City Council recently established a resident Stormwater Task Force to help guide this prioritization. The application deadline is Friday, Nov. 15 and can be found at www.fallschurchva.gov/TaskForce. This Task Force will work with City staff and engineering consultants to review floodwater data and history, rank possible solutions alongside costs, and present recommendations to Council on a prioritized list of stormwater projects. The criteria for ranking projects will include such things as the frequency of flood damage to property, public safety, and cost effectiveness. The timeline of work for the Task Force is to hold an organizational meeting in December, conduct its work in January and February, and present recommendations in March 2020.
Solutions may range from stormwater detention and increasing stormwater conveyance, to improved overland relief, bio retention, and other low impact solutions. For each project, we will use hydrologic modelling to measure the effectiveness of proposed solutions, and to demonstrate that relieving flooding in one area does not worsen problems downstream. Due to cost (as well as federal and state regulations) it is not possible to expand the entire City’s stormwater system to deal with an extreme July 8 type of event. But with a focus on reducing flood damage from the more frequently occurring downpours, we can improve our resilience to flooding.
Residents can consult with City staff for advice on how they can better protect their homes against flooding, such as positive drainage way from the home foundation, protecting window wells and basement stairs from surface water, and sewer backflow prevention. By the end of this year, the City Council will consider adoption of a new sewer backflow prevention cost share program for homeowners who have experienced repeated sewer backflows.
This effort will be focused on relieving flooding. In addressing flooding, however, the City will not turn away from its long standing commitment to environmentally based low impact solutions to stormwater. Low impact solutions, like bioretention, swales, tree preservation and tree planting, and home cisterns all contribute to healthier streams and reduced flooding, particularly from smaller rain events. Regulations on land use, such as home lot coverage restrictions and impervious cover limits (25 percent and 35 percent respectively for single family lots) will continue to play a crucial role in reducing flood damage.
The City maintains 70 miles of stormwater pipes in the City. Most were installed by private developers in the period between 1940 and 1970 while the City grew, subdivision by subdivision. Important parts of the City’s stormwater system were formerly country streams running through farmland, and these streams, now flowing through underground in pipes, have names — the Coe Branch, Reagan Branch, and Pearson Branch — which refer back to names associated with former farms. It is along these historic stream-ways that the City continues to experience the most severe and recurring flooding during periods of intense rainfall.
Over the past four years, the City has invested $4 million in your stormwater fees to improving stormwater detention, improving water quality to meet federal mandates, and improving the City’s natural streams. Now, with a warmer climate, which scientists say means these hard-hitting local downpours will be more frequent, we will increase our focus on using stormwater fees to invest in flood protection. The Stormwater Task Force will help us work through difficult decisions on prioritization of projects, with strong community participation. For more information: www.fallschurchva.gov/stormwater.
Wyatt Shields is the city manager of the City of Falls Church.