The Nature Conservancy: Big Woods Stream Restoration

April Showers

The temperature is topping 90 degrees again today in Eastern Arkansas. The Delta is finally drying out from extensive flooding of the Cache and lower White Rivers, which both reached levels unseen since the 1970's this spring. Our site held up beautifully despite the high water; we plan on re-surveying monumented cross-sections and longitudinal stream profiles this fall to measure rates of erosion or deposition within the new channel and floodplain.

It seems that, by mere chance, most stream restoration efforts get tested by some extreme weather event immediately following or during construction. Delta Project Manager Matt Lindsey (pictured below within our constructed "E6" stream type channel) remembers a project he worked on in the Gulf Coastal Plain of Mississippi during the summer of 2005. "When Katrina hit we got over 5 inches of rain on our site in a matter of a few hours and category 3 hurricane force winds. Needless to say, being in the middle of construction, this set us back a few weeks. After that, a 30-year flood event seems mild."

Connections Made

As of December 2007, Benson Slash Creek is again a free-flowing stream.  Over the past few weeks we have hydrologically connected Benson's newly-restored streambed and created a series of floodplain wetlands out of the century-old agricultural channel that previously confined its flow. Hydrostatic pressure transducers set within the stream and down in wells among the floodplain monitor the changes in site hydrology in response to restoration.

Phase 3 Commences

Last week construction began on Phase three of the Benson Creek Stream Restoration project. "This phase involves digging and stabilizing what is referred to is an E channel," says Delta Project Manager Matt Lindsey. An E channel is best described as a highly sinuous stream type with a low width to depth ratio (meaning that it is relatively narrow and deep).

In this case we are digging a channel that is around 3 feet wide and 2 feet deep. E channels are characterized by their natural box-like shape and often overhanging banks. Relying upon thick, deep root systems of riparian vegetation and a highly developed floodplain, the streambed and banks of E channels are highly stable, meaning less sediment entering downstream.

Here, Cache River Project Manager Josh Duzan and volunteer Holly Clinkingbeard (of Fayetteville, AR) install biodegradeable jute fiber matting over a bed of hay and native seeds. This will temporarily stabilize the stream while wetland vegetation takes hold.

Winter Break

As expected, work on the jobsite has stopped for the Winter, a time in Eastern Arkansas when seasonal rains flood streams and rivers and saturate the soil. Currently our stream restoration project is on schedule (half of the proposed channel has been excavated), and work will resume in the Spring with a completion date expected sometime this Summer.

    

Delta Rivers Rising

The winter rains are upon us and work on the jobsite has slowed accordingly. "It's hard to run an excavator when the tracks keep slipping underneath of you every time you attempt to dig in," says ecologist and expert earth mover Matt Lindsey. "Every job out here is more demanding when it gets wet."

With over six inches of rain falling within the past three weeks, streams and rivers in the region have begun to swell and even overtop their banks. "Delays due to high water are expected with any project in this eco-region," according to Josh Duzan who has been with Arkansas' Nature Conservancy chapter for three years and has watched Delta rivers rise and fall with the changing seasons.

"If there's one thing we've learned over the years, it is that you can't win a footrace with Mother Nature." At some point within the coming weeks, construction will halt until the rainy season lets up. The hope is that Phases I and II of the project will be completed before that time comes.

   

Installation of Log Sills

Our filter fabric came in last week, allowing us to place log sills at pre-selected stations within our channel. A sill is simply a large hardwood log placed perpendicular to flow at a riffle within the stream. Large woody debris (LWD) naturally plays an important role in delta streams and rivers, helping to stabilize the bed and channel, as well as providing habitat for macroinvertebrates and shelter for various fishes. Our log sills are designed to mimic naturally occuring LWD and provide these vital aspects ensuring that our engineered stream acts as a healthy and stable ecosystem.

Below: the installation of a log sill. Note the black fabric placed upstream of the sill; this keeps water from flowing under the log, thereby compromising its structure. The entire process takes from 1 to 2 hours.

Construction Underway

Josh here. We are at week three of the construction process, and it's exciting to see things coming together on the ground. After months of prep work (collecting and processing data from reference streams, site survey, hydrologic and sediment analysis, and natural channel design), implementation of the plan is finally underway. These two images show the same section of stream, one constructed on the ground and one as a schematic design.

A key aspect of stabilizing our new channel is ensuring that native vegetation roots within the channel and on the unconsolidated soil of the point bars. A cover crop of winter wheat comes up quickly and will hold the topsoil while live stakes, native grass, sedge, and rush plugs, bottomland hardwood seedlings, and native seed get established.