Resler Canyon Update

UTEP Engineering Professor John Walton recently gave a report to the Frontera Land Alliance regarding the erosion problems at Resler Canyon (the Wakeem-Teschner Nature Preserve). On September 7, Professor Walton wrote:

"I went to Resler Canyon this evening and looked over the status of the drainage coming into the upper portion of the canyon. This is a summary of my observations and recommendations.

The upper portion of the canyon is in a highly unnatural state. Storm runoff from developed portions of El Paso comes in at two major areas on the southeast and at least one location in the northwest. These areas are marked by enhanced, ugly, erosion of the arroyo sides. The enhanced erosion extends ¼ to ½ mile down the canyon until equilibrium is established. The damage is not limited to the edges of the property but rather is visible deep inside.

Development in the absence of proper engineering standards that are rigorously enforced causes an increase in peak and total storm discharge. Peak discharge rather than the total volume of water is usually what causes most erosional damage. The storm runoff coming into the canyon also has a low content of suspended sediments. In a natural system there is a dynamic balance between sediment load and erosion. Water with low sediment content is “hungry” and tends to pick up sediments (causes erosion) until a new equilibrium is established. An additional problem is that the slopes in the upper portion of the canyon are steeper than natural slopes because the tops of the arroyo were scraped and pushed off.

The multiple problems (unnaturally steep slopes, unnatural peak discharge, and unnaturally low sediment content) mean that a wholly natural solution will not work. A natural solution will mean essentially sacrificing the upper ¼ or ½ mile of the canyon. Left alone the arroyo will continue to erode at the edges and far into the interior of the property.

An engineering solution of some type will have to be applied at several locations. Given the high peak discharge and low sediment content the water must be slowed while coming into the canyon, the peak discharge will have to be lowered, and sediment will need to be trapped.

Ideally detention ponds would be built on the property of the upstream developments that have caused the problem. Unfortunately this is not feasible.

A realistic solution is:

• At (at least) the two major water inputs: Ugly engineered structures with energy dissipation above and small, decent looking, detention ponds below. They would have to be better built than the previous attempts.
• A series of rip rap erosion control structures (leaky check dams) extending ¼ mile or more down the channel to trap sediments and reduce peak discharge to a more natural level."