Erosion is the geological process in which natural materials, such as rocks and soil are worn away and shifted by forces, such as wind or water.
As erosion along the Brazos River continues to be a concern in Fort Bend County, Precinct 4 Commissioner Ken DeMerchant, along with Precinct 1 Commissioner Vincent Morales and Chief Drainage Engineer Mark Vogler, is taking steps to unite with local leaders on solutions.
“We continue to have problems with the Brazos River. We’re lucky at this time [during Tropical Depression Imelda] the river was at a low level,” DeMerchant said during a Sept. 24 Commissioners Court meeting.
From Imelda resulting in a 4-foot rise in water level in the Brazos River, to the 2015 Memorial Day flood dumping 11 inches of rain in the area within eight hours and Hurricane Harvey devastating Greater Houston in 2017, erosion has remained top of mind.
Bordering the Brazos River, there are nine levee districts in Sugar Land, protecting about $15 billion in property, according to Fort Bend County Appraisal District market values.
“I think we can see that we continue to have problems with this erosion throughout the county, and I think we need to take more of a regional approach to it,” DeMerchant said.
DeMerchant is moving forward with an agreement for engineering services to improve Oyster Creek in Precinct 4, which feeds into the Brazos River. Results from the Nov. 5 election will tell whether several bond initiatives, both from Sugar Land and Fort Bend County, will be approved by voters to mitigate flooding.
However, specific projects relating directly to the Brazos River are lacking in both bond programs.
Much of the funding necessary for erosion mitigation would fall on state and federal government requests, Sugar Land assistant city manager Chris Steubing said.
“Through all of this work, the city and Fort Bend County have been working together, and we will continue to support the creation of a committee that will help bring attention and funding to address this issue,” Steubing said.
The city of Sugar Land commissioned a study along the portion of the river running through city limits, and eight critical areas in need of attention have been identified. The city also implemented its own system of rain gauges over the summer to better measure river levels within city limits.
UNDERSTANDING THE PROBLEM
In 2019, heavy rains on May 7 and Sept. 19 caused isolated flooding and numerous road closures as storm drains were inundated with water. Harvey caused a spike in the rate of erosion along the Brazos River.
Although isolated events, such as the May 7 storms and rainfall from Imelda, have had little effect on erosion along the river, rainfall events occurring upstream from Fort Bend County can create major flood stages and high flow rates, Steubing said.
A spike in the migration rate of the Brazos River rose to nearly 46 feet in 2017, second only to a 50-foot migration rate peak in 1957, as measured since 1953, according to Sugar Land’s erosion study.
The migration rate refers to the interpretation of the river’s movement based on flow data and aerial images, Steubing said. Data shows as the flow of the river is faster, the migration rate is increased accordingly.
“Higher flow rates equals increased chances of erosion, and [in] the middle years we saw fewer major river events, [and] therefore less chance of erosion,” Steubing said. “This has all changed with the recent events back in 2015 to current day.”
Taxing entities, such as levee improvement districts—political subdivisions that cover specific areas of land and provide flood protection, create drainage improvements and reclaim land from flood plains—also have projects of their own in the works.
LID 19 in Riverstone has several post-Harvey projects that have been completed and are ongoing as well as projects that are on hold or will begin in the future. Projects include items such as the $7.67 million Steep Bank Creek Pump Station expansion.
Many Greatwood residents were concerned about whether there was enough pump capacity during the May 7 flooding event that inundated storm sewers. LID 11 officials said the pumps were fully operational during the duration of the storm, but the heavy rain did result in street ponding.
Although LID 11 does not require additional pumping capacity, the board of directors elected to increase the capacity of each of its two pump stations and construct a third pump station.
“LID 11 is located along a segment of the Brazos River that does not have significant bank erosion problems at this time,” the board of directors said in an emailed statement. “We are hopeful the county and city can find an equitable solution to the problem areas without increasing erosion in the areas adjacent to LID 11.”