Check Dam Erosion Control at Palisades

 

Palisades Erosion Control Project Grand Canyon National Park

Novemeber 2, 1995 - Video Clip Duration 04m:40s

Palisades is one of the largest river terraces along the Colorado River formed by debris flows from Palisades Creek and abundant sand left by Colorado River floods.

This broad, relatively flat delta is rich in cultural resources, containing the remains of numerous pueblos, fire features, wall alignments, and artifacts.

Their condition has been deteriorating due to severe erosion caused by arroyo and gullying cutting and the loss of sediment due to the existence of the Glen Canyon Dam.

The greatest amount of impact occurs from run-off channels that cut through these cultural deposits on their way to the Colorado River.

These drainages that empty directly into the river are referred to as river-based streams.

These streams constantly expose new features and destroy others.

Because of this continued erosional downcutting, remedial actions were warranted to decrease the erosional process and the loss of cultural material.

A team approach was adopted by the signatories to the Programmatic Agreement. Three years of discussions and visits to the area by Programmatic Agreement representatives and National Park Service archaeologists” resulted in a plan of action.

In May, 1995, a four day stabilization workshop at Lee’s Ferry was organized, centering on a remedial action plan for Palisades.

The general thought was that Palisades needed erosion control measures that would enable sediment from the drainage systems to be captured, thus stabilizing the cuts.

A sediment catchment system would, theoretically, not only lessen the erosion of exposed features, but also preserve features and materials below the surface.

On-site evaluations and implementation of these erosion control measures were scheduled for September, 1995.

 

The video clip shown on this page begins here:

The methods used for sediment and erosion control were initiated by a Zuni Soil Conservation team and National Park Service resource specialists. They were assisted by members of the Hopi Tribe, the Hualapai Tribe, and the Navajo Nation. Other participants included personnel from Northern Arizona University, the Arizona State Historic Preservation Office, the United States Geological Survey, and the National Forest Service.

In total, 26 people were involved with this “hands-on” erosion control project.

The group walked through each arroyo and discussed where and what type of action should be taken.

After a consensus was reached, the location for each checkdam was numbered and described on flagging tape. Detailed descriptions were recorded and photographs were also taken.

National Park Service archaeologists made certain that all dams were built with culturally sterile materials found in the vicinity, and that no subsurface cultural features were disturbed.

Materials gathered for checkdam construction included: camel thorn, low brush, and arrowweed. Also collected were driftwood logs and branches.

River cobbles and boulders, limestone and sandstone boulders, and lava cobbles were carried in buckets, or on rock litters.

Over 100 tons of rocks were used to complete the project.

The sediment catchment structures were made in five varieties:

rock alignment, log checks, rock checks, “horseshoe” checks, and “basket weave” checks.

The “basket weave” check was the most elaborate type to be built. First, driftwood posts were cut and shaped.

Then, the posts were pounded into the ground to form the outline of a rectangle.

An abundance of brush was then placed on the floor of the arroyo between the posts.

Then, the arrowweed was forced into the side walls of the arroyo and woven through the driftwood posts.

The weave was repeated until it almost reached the top of the posts.

 

Large and small rocks were selectively placed inside the basket to give additional support.

To finish the check, rock grades were placed on both sides of the basket.

In three days, a total of 70 checkdams were built. The amount of labor necessary was considerable.

The Palisades erosion control project represents the first, and the most intense, of several erosion control assignments to be completed along the river corridor.

The effects of these measures will be monitored in the future, and if they prove to be successful, similar methods will be employed on highly impacted sites.

This archaeological preservation effort is unique because it utilized the expertise of both Native conservators and federal agency preservationists.