Story by Wade Day, Public Affairs Specialist, San Angelo, Texas

Texas weather is fickle. For a state this size, it boasts a tremendous amount of diversity in our landscape and the natural resources contained within it. Weather patterns and rainfall can vary widely, and depending on the soils, topography, and vegetative cover, the impacts can be extreme. While we all have probably found ourselves praying for rain, multiple areas of the state have received excessive amounts of rain in a short period of time. Areas in the Hill Country and more recently in South Texas near Uvalde, have had rainfall events that caused flooding and damage. Though infrequent, these events are part of the process of nature.     
 

Prevention

The U.S. Department of Agriculture (USDA) Natural Resources Conservation Service (NRCS) has been working to control these types of flooding events through the use of flood retardance structures, or in more common terms, earthen dams. Much of this work started with the passing of flood control acts in 1936, 1944 and 1954 by Congress, who then assigned responsibility of the Watershed Protection and Flood Prevention Program to the NRCS. These acts allowed for the construction of nearly 12,000 flood retarding structures in the U.S. Currently, there are almost 2,000 dams within 139 watershed projects across Texas. The watershed projects encompass nearly 6.2 million acres and provide nearly $600 million in realized annual benefits. 

It would be easy to assume that these structures are only located in the eastern portion of the state, but that is not the case. While the largest concentration of these flood structures is in the I-35 corridor, they are found throughout the state. Every region of Texas has these for flood retardance. The Panhandle region northeast of Amarillo, South Texas between Corpus Christi and Laredo, the Hill Country and even far West Texas in Sanderson have flood retardance structures to help control flooding.
   
Much of the work done toward flood prevention occurred from the 1950’s through the 1980’s. Though other structures have been built since, the bulk of the work happened during this period. Easements were granted to the local Sponsors by landowners for the construction and function of the flood control structures. While the Federal government provided the technical design and funding for construction, the local Sponsors are responsible for the ongoing operation and maintenance of the structures. 

Function

The majority of these structures are earthen dams located on private properties, unseen to the public. Though they may be unseen, their importance cannot be overstated. Their primary purpose is to protect lives and property by reducing downstream flows during and after large rainfall events. The flood retardance dams were constructed on upstream tributaries flowing into larger water sources. They temporarily store floodwater after heavy rainstorms, slowly releasing it over several days. This slow release is the key. It helps to control flooding by reducing the flow and the devastating effects it can have.

Confusion sometimes arises from the intended purpose of flood control structures. Many of the structures have an area of water impoundment that makes large ponds or small lakes. These are often utilized for livestock watering or recreation, but this is not their primary focus or reason for construction. 
 

“It's the controlled release of the water to prevent flooding downstream,” said Shane Ice, NRCS Texas State Conservation Engineer. “So yes, they may have temporary storage of a lake out in front of it, but that is not their primary intended purpose. They are for flood control, to the point that it could be safely released downstream, and storage of sediment that would have otherwise been transported downstream.”
 

This line of reasoning can be seen in the events that unfolded in the Uvalde area recently. Approximately 26 inches of rain fell within the 3 days between July 14 through July 17, well above the yearly average for the area. Though flooding still occurred, it was not a large gush of water. It was a more controlled release that did not cause severe erosion, massive movement of debris and sediment, and loss of life and property. This can be attributed in part to the flood retarding structures that operated as designed and held back the wall of water that could have been. Three flood retardance sites are in operation in the immediate area affected by this event. Installed in the 1980’s, their purpose is to protect the city of Uvalde. At the time of their installation, they offered an economic benefit of around $177,000. Today, that number is closer to $3.1 million dollars for the protection they provide. All three sites were successful in their function. They were able to slow down water and prevent the devastating effects of flash flooding. Other surrounding areas and similar structures reported similar results. Flooding is inevitable with large amounts of water in short time spans. Flood retardance structures are not intended to stop flooding completely. Their purpose is to slow rising water down and release it in a controlled manner. In this case, mission accomplished. 

Ongoing responsibility

For these structures to continue functioning properly, on-going care and maintenance is a reality. Everything from yearly inspections, repair of minor damage, to full restoration and rebuilding are all part of what keeps these structures ready for the next flooding event. While much of the physical labor needed for operation and maintenance is the responsibility of the sponsor, NRCS continues to serve as a technical agency and at the request of the sponsors provides recommendations for maintenance and repair needs of the structures.

“Although the sponsors are responsible for the operation and maintenance, we still provide assistance with inspections, technical information and recommendations as needed,” said Karen Green, NRCS Texas Dam Safety Engineer. “If they have a question, need help with evaluating any damage or issues with them, we are available to assist them.”

An area of concern that shows a need for public education is urban encroachment on flood retardance structures. In many cases, the original design and purpose was to protect agricultural lands. Where cropland, pastureland or small rural communities were the initial target, they have been replaced by urban sprawl in many areas. Nearly 60,000 people now live downstream of some type of flood retardance structure, a far cry from the original design. Though they can still perform their intended function, care must be taken not to alter the structure itself or the land directly adjacent to them. Development in close proximity to these structures can have the unintended consequence of cutting-off access to the structure. Both personnel and heavy equipment need access to all areas of the structure to perform maintenance and keep them operating correctly.

“More attention should be given to these flood control structures and development around them,” said Green. “As much as possible, development right up next to the dam or directly downstream needs to be restricted to allow for continued operation and maintenance needs.”

Understanding the function of these structures is paramount to their continued care and purpose. Areas in and around these structures have a high likelihood of flooding at some point. Building homes or structures in areas with flooding potential is never a good idea. Before any construction starts or alterations are made to the land surrounding these structures, the local sponsors should be consulted. By doing so, problems or issues can be avoided.

“Contact the sponsors. They own the easements around the structures and are the first line of information,” is the advice from Green.

Flood retardance structures perform a vital service to Texas. Their care and maintenance are essential to both the rural and growing urban landscape, helping to curtail the devastating effects of flooding. NRCS delivers practical, voluntary, and locally led conservation solutions that help producers conserve natural resources, strengthen agricultural production, and keep working lands productive for generations to come.