176 



.,,, additional by-pass channel 01 

 conduit 10 save ihe natural values ol 

 ihe existing > hannel. 



1 eatures thai can improve habitai 

 in damaged <» modified channels can 

 include sills (low structures to create 

 upstream pools 01 downstream 

 5C ours); deflectors foi developing 

 scour holes and riffles; roi k < lusters, 

 .nul covei devi( es su< h .is brush mats 

 anchored to banks io provide fish 

 habitat; and structures to enhance fish 

 passage sui h .is lisli ladders. 



■ CHANGES IN SITE DRAINAGE 

 OR LAND MANAGEMENT 



Before a stream restoration techni- 

 que can be prescribed, the cause of the 

 problems must be identified and cor- 

 rected. Usually the problem can be 

 traced to excess run-off from urban 

 development (such as paved roads or 

 residences) in the watershed, or pro- 

 blems with culverts, or land manage- 

 ment activities such as clearing of 

 riparian vegetation. Perhaps nearby 

 grazing has damaged a stream 

 corridor. 



Run-off from buildings can be re- 

 tained on-site in appropriately 

 designed retention basins, permeable 

 landscaped areas or rainwater 

 cisterns. Culverts are frequently 

 clogged, undersized, or put in at the 

 wrong slope, resulting in damages 

 upstream and downstream of the 

 culvert. Sometimes it can be advan- 

 tageous to remove culverts and 

 reslope the channel banks to restore 

 the channel to a more natural 

 geometry. Occasionally, concrete 

 fords can be used in lieu of culverts 

 for road crossings. Bank erosion, 

 vegetation denudation, downstream 

 sedimentation and instability caused 

 by grazing somewhere in the water- 

 shed can be dramatically and quickly 

 remedied by fencing the livestock 

 from the channel. 



Sonoma County, California. Friends of 

 Sonoma Creek select and remove 

 obstructions in the creek to prevent 

 undesirable deflection of the stream flow 

 and increase channel capacity. 



■ CHANNEL CLEANING AND 

 OBSTRUCTION REMOVAL 



Urban streams can be notorious for 

 the garbage, junk and debris they col- 

 lect, ranging from old stoves and 

 shopping carts to log jams. Removing 

 these obstructions can not only 

 significantly change the aesthetics of 

 the stream, but can also bring signifi- 

 cant flood damage reduction benefits 

 by increasing the capacity of the 

 stream channel and lowering the stage 

 of flood waters. Selective clearing of 

 vegetative growth and branch and log 

 snags is a long practiced strategy of in- 

 creasing the channels' capacity to pass 

 flood flows. The Stream Restoration 

 Program funds neighborhood 

 organizations or volunteer groups to 

 maintain channels and instill a sense 

 of stewardship for the stream as a 

 valuable natural resource. As a part of 

 this effort, the program supports 

 public education efforts and school 

 programs. 



Snagging and clearing proposals 

 must be planned with the assistance 

 of biologists who can ensure that the 

 project will be both enhancing the 

 habitat values of the stream while also 

 increasing the channel capacity. An 

 excellent guide for the design of snag- 

 ging and clearing projects is Stream 

 Obstruction Removal Guidelines, cited at 

 the end of this pamphlet under "Ad- 

 ditional Sources of Information". The 

 objectives of selective clearing and 



