What is erosion… and why should I care?

A significant portion of the Irving Flood Control District Section III (IFCD3) construction and maintenance budgets is spent on addressing the results of erosion. WaterWays recently visited with Dallas Burke, who leads operations and maintenance for the District, to learn more about the whys of erosion and what’s being done to deal with the resulting challenges.

WaterWays (WW): What is erosion and why does it need to be addressed in operating IFCD 3?

Dallas Burke (DB): Erosion is the natural action of water, wind and gravity breaking down soil into fine silt, then transferring it to another location. Erosion causes two events that are important issues to IFCD 3. First, erosion changes the ‘lay of the land’ adjacent to our flood control waterways. Second, silt created by this process generally finds its way into our flood control operations.

WW: Why does erosion in the ‘shorelines’ along flood control facilities throughout Valley Ranch matter?

DB: Simply put, erosion can change the direction and speed in which water moves from its landing place during rain, sleet or snow storms to where it needs to go – into canals, creeks and other bodies designed and constructed to move storm waters to the Elm Fork of the Trinity River. Any change in this intentionally developed route could impact the effectiveness of our flood control capabilities. Left uncontrolled, property adjacent to our flood control facilities could be drawn into the creek, canal or sump. This loss of a defined shoreline and stormwater storage is bad for the Valley Ranch community.

WW: Going further, why is silt a concern to IFCD 3?

DB: Silt starts as solid dirt, frequently along the shoreline of ponds, canals and other water-holding facilities in the District. As water from rain, ice or snow passes over any dirt not protected by a physical barrier, such as a wall, or by turf or other grasses along these water structures, it gets lifted off the surface and carried into the adjacent waterway. During this process, the dirt is broken down in size, just like what ends up in your sink when you wash your hands after gardening. Silt from along the shoreline is carried downstream until the speed of the current slows enough for the silt to fall out of suspension in the water, depositing it on the bottom of the creek, canal or sump. The more silt that fills the bottom of these waterways, the less space is available for storm water to be moved through the system to the Elm Fork, changing the efficiency and capacity of our system.

WW: What’s the solution to silt entering the IFCD 3 system?

DB: Prevention is a major key. Maintaining natural plant barriers and artificial walls of masonry or cement, as well as keeping the land adjacent to shorelines planted in healthy turf grasses, makes a difference. As a result, precipitation has less ability to gather and carry dirt into our creeks, canals and other flood control features. Careful management of these ground sources reduces silt entering our system to mainly wind-borne sources, which is relatively minor.

WW: Once silt is in the system, what do you need to do?

DB: As you may have recently noticed, we’ve been removing silt from the bottom of the Ledbetter Sump, which serves as a holding area for water before it enters our pump station for release into the Elm Fork. This removal process, called dredging, removes silt from our waterways and transfers it to a storage site to dry. Once dry, the silt can be returned as solid dirt to fill low areas where it originally started the journey into our facilities.

WW: Thanks, Dallas. In a future installment of WaterWays, we’ll take a look at closer look at dredging in the District, both past and present. In the meantime, the IFCD 3 website, Facebook and Twitter are sources of more information about and means of engaging with Irving Flood Control District Section III.