River Restoration 1 basic concepts 2 restoration of LWD 3 what are natural conditions restoration reestablishing structure and function of ecosystems ecosystem as close as possible to pre disturbance conditions rehabilitation making land useful again after disturbance not necessarily predisturbance condition reclamation intended to change biological capacity of a system ecosystem is definitely changed river engineering is an old idea flood control power etc river restoration is newer often driven by interest in restoring habitat but how do we do it morphologic controls riparian veg flow obstructions rate of change hydrology sediment wood inputs Channel morphology geology gradient fast catchment vegetation valley form slow conceptual model 1 climate general restoration considerations conceptual model 2 more specific to restoration Geology Climate Regional Vegetation Flow Regime Sediment Regime Wood Regime Land Use Pollution River Engineering Floodplain Development Restoration LWD Habitat Structure Dynamics Biotic Condition creature viability salmon habitat restoration model 3 supply of water sediment wood salmon habitat fluvial sub environments river environments we might consider stream habitat scales at what scale do we want to restore basic river restoration steps general steps for a particular site 1 2 3 4 assessment diagnosis what needs restoring design how to accomplish this implementation accomplishing it can be pretty slow monitoring is it working context context context spatial what kind of stream is this braided meandering cascade step pool pool riffle temporal what was the disturbance history dam logging channel management when restoration of LWD LWD large wood y debris wood acts as an impediment to flow can cause flow convergence and scour pools that provide important habitat or can cause slower flow aggradation sediment buildup global forests forests have covered about one third of the Earth s land surface during the Holocene last 11 000 yrs but we have changed the extent of forest cover substantially Oregon Amazon Cameroon global forests few of the worlds forests retain frontier conditions remaining large intact natural forest ecosystems undisturbed and large enough to maintain all of their biodiversity GFW global forests Much of our understanding of river systems was developed in areas that either lacked large wood or that had been cleared of wood debris To what degree are our perceptions of the role of wood in rivers due to this legacy Snags on the Missouri Karl Bodmer circa 1850 de snagging log jams were significant obstacles to navigation and land development in the western US LWD at pool riffle scale more wood more pools For channels surveyed in AK and WA plane bed morphology occurs only at low LWD loading LWD can control the formation of pools and bars and thereby channel reach morphology LWD valley scale Log jams trap large amounts of sediment and can lead to aggradation along entire channel reaches LWD valley scale Both locally recruited trees and log jams delivered by debris flows can create alluvial valley bottoms in confined mountain streams Valley jam Position in Channel Network Queets River Washington Log steps Meander jam Bankfull bench Watershed Scale LWD across scales LWD is important for channel morphology 1000 Valley Bottom 100 Years 10 1 In Channel Pools Cover Bank Complexity 1 Reach Channel Switching Islands Sloughs 100 Spatial scale meters Water Sediment Wood Routing 10 000 larger logs typically key members of log jams but all sizes are important log diameter channel depth LWD size 2 key 1 racked 0 loose 0 1 log length channel width 2 LWD restoration restoration of natural wood loading would take centuries large key members take a long time to grow so reintroduction of large woody debris Cowlitz River Engineered Log Jams 25 yr flood event 5 weeks after construction Changes at the Cowlitz Site 12 95 to 04 97 Uvas Creek january 1996 so need to be careful designing restoration july 1997 Uvas creek did not want to meander was that it s natural state Uvas Creek restoration context context context 10 commandments of river restoration according to Dave 1 2 do no harm look beyond the channel to assess it in its context 3 use native materials 4 emulate natural analogs 5 let channels do the work 6 let the channel use its floodplain 7 manage inputs to the system so that the river can fix itself 8 use direct manipulation of the channel as a last resort 9 allow for the river to make its own changes 10 use qualified appropriate personnel to design restoration efforts
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