This project resulted in the restoration of stream function and form for over 200 m (600 ft) of Sulphur Creek.  The stream is no longer straight, and the high right bank is no longer delivering sediment to the “Redding Redds”.  The channel is still incised within the alluvial valley but within that area there are now two gentle meanders with riffle and pool features.  Because the natural gradient and substrate has been restored, the channel is now more accessible to juvenile salmonids which migrate downstream during seasonal low flows, and structures along the bank now provide resting areas during high flows.  During the winter of 1999-2000, the stream “settled in”, scour pools formed as intended, and many other changes occurred in the channel.

The removal of the excess sediment within the streambed resulted in channel adjustment approximately 200 m upstream from the restoration reach.  The stream “head cut” through previously embedded bed materials, and this change in the channel led to the formation of gravel bars.  The composition of the bars is desirable spawning material.  Because the aggraded streambed was lowered during restoration, the backwater from the Sacramento River remains in the lowest portion of the project reach for a longer period during the dry summers, and this also aids in the escapement of salmon juveniles.  Streamside vegetation is quickly establishing now that more water is available during the summers. 

Ideally, the entire sandbar should have been completely removed.  However, a small section of the sandbar was left in the upper portion of the project reach due to a combination of time constraints, lack of funds, and the presence of mature cottonwoods nearby (there were concerns that disturbing the soil too close to the cottonwoods would damage their root systems).  The stream has subsequently incised the left bank of the sandbar.  This section of sandbar will probably continue to erode as the stream reaches equilibrium.  Both bends in the completed channel have scour pools and much habitat complexity among the vegetated riprap and rootwads.  There is overhanging vegetation and cover, and the different species of willow and other native plants have created a diversified riparian habitat.

The boulder cluster was subsequently buried by sand and gravel.  The boulders did not encourage scour nor did they provide any habitat value.  As expected, the backwater effect coupled with the sediment load caused the boulder cluster to behave more like a dam, forming a gravel bar both upstream and downstream.

The cross-overs occurred where they were expected.  The meander that was designed for the channel worked well, and the rootwad and vegetated riprap structures along the streambanks were also accurately designed.  The elevation of the rootwads with the water level coincided with critical fishery periods in this seasonal stream. 

At one section of the stream, there was approximately 10 m (30 ft) of visible bank erosion.  This was not the result of improper alignment of the channel, but was the result of insufficient bank protection in this section.  During one of the organized “planting days”, volunteers built a 10 m long (30 ft) brush mattress to protect this bank.  However, the mattress was not properly secured at the upstream portion to contend with high flows.  The flows got around behind the mattress and the entire mattress was ripped from the bank, a common predicament if a brush mattress is not firmly secured.  However, a 3.3 m (10 ft) long brush mattress that was constructed by Watershed Restoration students on the opposite bank did very well, surviving extremely high velocities, with abundant growth of willows.  This brush mattress was specifically secured to existing vegetation on the bank, and firmly secured to the bank so that the high flows would not scour behind it.

Supplemental irrigation was not available for the project, and summers in Redding are typically very hot and dry, with no rainfall.  As a result, almost all container plants that were planted high up on the banks in hot, exposed areas failed, with the exception of a few drought-tolerant species.  The majority of the rooted container plants (cottonwood, elderberry, and upland species) had higher survival rates in partially shaded areas.  Contrary to expectations, willow container plants did not have a higher survival rate than willow stakes, although all seemed to survive better in shaded areas rather than hot, exposed areas.  The deeply planted live pole cuttings and brushlayers were very successful, with a 90% success rate.  These were planted deeply into the vadose zone.  It was also interesting to note that willow cuttings and basket sedges had survived over a month of complete inundation from the backwater.  Almost all of the cottonwoods (poles and container plants) that were inundated under the backwater were eaten by beavers.

Two of the modified live siltation structures failed when the 10 m (30 ft) section of bank scoured, but two persisted and are growing vigorously and behaving like small vegetated bendway weirs.  These structures survived the first season, although they were inundated for at least a month by backwater, they withstood an estimated 4 m3/sec (12 cfs) velocities, and they were buried only about .3 m (1 ft) into the channel.  The experimental brush box, which consisted of live stakes and dead brush, was partially washed away, although what remained was growing well. 

The native grasses achieved about 70% cover and were going to seed after 1 year.  There were not many weeds amongst the grasses.  The basket sedges were also establishing well, and have withstood extremely high velocities.  The biodegradable straw erosion control blankets actually did biodegrade in one season.  The basket sedges planted in the blankets did not survive, but this was probably due to the dry location on the upper left bank.  Cattails and rushes are naturally revegetating the stream channel.

The stream is now more accessible to visitors since there is now a gently sloping right bank where there was once an unstable vertical bank.  The left bank is also more accessible now that the non-native blackberry growing in the sandbar has been removed.  Students from kindergarten to college will be able to view the project (and migrating salmonids) and hear presentations from Turtle Bay Museum guides on the various aspects of stream restoration and natural resource management.
 
 

McCullah, J. M., 2000. Bio Draw 1.0 – Compendium of Biotechnical Soil Stabilization Practices, Salix Applied Earthcare.
Rosgen, D., 1996. Applied River Morphology, Wildland Hydrology.