THE LAND CONSERVANCY OF SAN LUIS OBISPO COUNTY

Restoration Project: Multi-Faceted Restoration

Upper San Luis Obispo Creek

Overview/History

Among the Land Conservancy's largest restoration projects is the work done on upper San Luis Obispo Creek in partnership with Janet Andrews (see Local Stories page). We met Janet at a flood control advisory committee meeting and learned of the extensive bank erosion happening on her family ranch. Changes in the watershed upstream had caused downcutting of the channel and a systemic erosion problem for the area. The Land Conservancy saw this as a good opportunity to do a large scale project in an important part of the watershed.

The Problem

Problems identified on the site from earlier studies were the extensive sections of eroding banks, long sections without shade for the creek, a lack of pool habitat, and damage to stream banks caused by grazing livestock. We set out to address all of these problems. In total, we repaired approximately 600 feet of eroded streambanks, installed 12 in-stream habitat structures, fenced livestock out of 3/4 of a mile of the stream, and built an alternative water system for livestock.

Project Approach

We used 2 methods for stabilizing eroded banks, both of whcih are based on re-establishing native streamside vegetation. On 2 stream banks we graded the slopes so they would support vegetation and installed native plants. The lower banks adjacent to flow were protected with coir biologs, made from shredded coconut husks, and live willow staking.

One steep stream bank was repaired using brush layering, a natural restoration approach that is reffered to as bio-engineered. On this bank, the toe of the bank was protected with rock material and live willow staking. We also used rock to make some redirecting structures that help steer the water away from the bank toe. The rocks we chose are a highly graded, meaning they are of varying sizes. Using well graded rock helps because if any single rock is moved by water, another can fall into its place, keeping the structures functional. Above the bank toe, a series of layers comprised of live willow cuttings are placed between layers of compacted fill wrapped inside a coir netting.

To address the shortage of pool habitat, we installed 12 in-stream structures to create pools. Several structure types were used including cross-vanes, J-hooks, and rootballs. These use the water velocity in the channel to scour pools for fish. Some of these structures did better than others, but we did get a good distribution of pools throughout the site.

Animal management on the site consisted of fencing that closed 3/4 of a mile of the stream to grazing livestock. While livestock can be effectively managed for the benefit of streams in many cases, we chose to close this one because the channel was so steep and deep. The trampling of the banks in these steep channels is problematic. Along with the fencing, we installed a solar-powered watering system that serves the cattle on site. We did leave gates along the site so cattle could be allowed access if the water system is down for any reason.

Challenges

This set of projects required the de-watering of the stream in several locations. Diverting a stream into a pipe is easier said than done. In somen cases, the gradient of the stream made this very difficult as sub-surface water would emerge into the channel downstream of the diversion. In this case we had to use multiple pumps to separately manage clean stream water and turbid water from the work zone. Working as a team with our contractors, we came up with ways to solve our problems with water.

Results

The formerly eroded banks have all done very well and are now covered in vegetation. The performance standards set before construction have all been met. The pool structures met with varying success, but the distribution of pools on the site is good. We learned a few good lessons on how to build better pool structures.