Winter Creek Stabilization & Enhancement Project

University of California, Berkeley
Fall 2009

Winter Creek is a seasonal tributary to Strawberry Creek, which flows through the UC Berkeley Campus.  The project reach of Winter Creek flows through the Mather Grove of redwoods in the UC Botanical Garden.  The upper watershed has been altered through increased impervious surfaces and drainage consolidation.  The channel through the redwood grove experienced recent rapid incision, causing bank sloughing, slides and rotation, which in turn threatened the redwood grove and associated facilities. 

In 2005 Hanford ARC contracted with UC Berkeley to install temporary stabilization measures to prevent further incision while a permanent solution was developed by the UC, Philip Williams Associates and Leahy Engineering.  In 2009 Hanford ARC was awarded the contract for the restoration and stabilization.

The 400’ long project included two segments, upstream and downstream of a footbridge.  The lower portion of the channel work included reconstruction with five step pools tying into a culvert inlet, a brush mattress and a section of vegetated soil lifts.  The upper section included nine step pools and a 60’ section of gabions lining both banks and the channel bed.  The gabion basket structure was complicated, and included several types of fill material, soil, fabric lining, landscape boulders and many angle cuts to create a meander and stepped banks.  The upper end of the gabion structure acts as a headwall.  We extended the existing culvert using a new 5’x5’x6’ junction box and 30” HDPE pipe.

Through the length of the project, additional stabilization measures included coir fabric, willow and dogwood staking, planting and mulch.    We installed an irrigation system to water the newly planted areas. 

We faced several major challenges to construction.  The Botanical Gardens is heavily used during the summer, and specifically, the amphitheater within the Mather Grove is used for several weddings every weekend during the summer and fall.  Although the grove was closed during construction, the UC planned to open the grove for weddings throughout the project.  This parameter meant that we were required to maintain safe and attractive public access throughout construction, along the same path as our equipment access.

Besides access and site appearance, equipment access to the channel itself was very narrow.  Once we navigated our excavator into the channel, we shuttled rock and soil to and from the excavator with tracked skid-steers, in a leapfrog fashion.  The slope was such that one skid steer shuttled from the staging area to the top of the slope, and the other shuttled material from the base of the slope to the excavator.  This process was tedious and required careful maneuvering between high value, museum plants and trees.