Riparian Restoration


Chambers and Miller, Ch. 9


Restoration success depends on understanding:

1) the processes that structure the ecosystem

2) the appropriate temporal and spatial scales

3) the effects of historical and ongoing land use.


Livestock grazing is implicated in most disturbances


Livestock influence riparian ecosystems by:


          1) removing herbage (allowing soil temp to rise and evaporation to increase)

          2) damaging plants by grazing, trampling

          3) altering nutrient cycling by depositing N and removing foliage

          4) compacting soil, which increases runoff and decreases water availability to plants.


Other disturbances: roads, recreation


There have also been long-term climate effects (drier, warmer).


Combined climatic and anthropogenic effects:


          1) many streams have become isolated from their floodplains

          2) surface water/ground water interactions have been altered

          3) declines in water tables have resulted in changes in plant species composition



Spatial Scales


Watersheds: drainage basins.


Riparian Corridors: integrated networks of stream channels and adjacent floodplains and terraces. 


Valley Segments: have semi-uniform slopes, widths and geological materials.


Stream Reaches:  have relatively uniform channel morphology, bed materials, bank conditions and woody debris.



Successful strategies for restoration are at watershed/riparian corridor scale.


Projects are at the valley segment/stream reach scale.


The most sensitive basins have the quickest and most negative response to disturbance and high-volume runoff.


Basin types:


Flood dominated    high sensitivity


Deeply incised                 low to moderate sensitivity


Fan dominated                low to moderate sensitivity


Pseudo-stable                  moderate to high sensitivity





Briggs, Riparian Ecosystem Recovery, 1996












Grazing may be less the problem than overgrazing.


One heavy grazing on sensitive land can be bad


          steep slopes

          shallow soils

          low vegetation cover




          alters plant competition

          decreases soil infiltration

          increases soil erosion

          stream characteristics modified:

                   loss of bank undercuts

                   increased turbidity


Livestock Management to decrease riparian impacts


          decrease grazing intensity



          develop upland water sources


Re-vegetating livestock-damaged areas


          You must first analyze:              1) channel stability

                                                                   2) water availability


          Understand the potential for autogenic re-vegetation


          Livestock and re-vegetation are not compatible


                   Plants palatable to livestock must be protected for the first two growing seasons.


                   Non-palatable species should be protected from trampling.




Hiking, camping, off-road vehicles




          loss of vegetation

          lowered organic matter

          increased erosion

          loss of macroporosity


ORV’s cause the same changes, only quicker.


Managing recreation


          adjust use levels

          keep trails and campsites away from sensitive areas (easily disturbed sites, new restorations)

          confine camping to a few sites

          install interpretive signage


Do not install a restoration project without controlling use


          live stakes may be used as firewood

          seedlings may be run over by vehicles

          irrigation systems may be torn up.




Southwestern invasives include salt cedar (Tamarix), Russian olive (Eleagnus) and Bermuda grass (Cynodon).


Usually they come to dominate after hydrology has been modified (salt cedar does well in artificial flow regimes).


Invasives negatively impact restoration efforts.


Salt cedar control


          bulldozer (where there are no natives)



Typical control regime


          Cut trees down in fall (cut 5 cm above ground)

          Paint cut cambium with Garlon or Tordon within minutes of cutting

          Re-cut and herbicide sprouts within a year.






Some wildlife impact restorations


          Some eat vegetation:



          white-tailed deer



          Some will gnaw irrigation lines:


          rice rats

          wood rats

          pocket gophers


Protecting restoration from wildife:


          Provide beaver with alternate food sources

          Build beaver cages out of chicken wire or hardware          cloth


Water Availability


Revegetating riparian sites characterized by groundwater decline



Low water availability occurs where groundwater levels are 3m or more below the surface.


          Planting riparian plants there is difficult.


          Survival rates are low.


Sources of decline:


          ground water pumping


          agricultural irrigation

          non-native phreatophytes


Plant material must be matched to site


          Planting riparian species may no longer be practical

          Flood plain spp. may be more appropriate:

                   mesquite, palo verde, hackberry

          Riparian spp. may not have enough water:

                   willows, poplars, walnut, ash


Planting Techniques


Seedlings may be especially vulnerable to low water availability.


Available moisture from spring flooding dries up quickly with onset of summer.


          Roots of seedlings must keep up with the retreating zone of soil saturation.


          Timing of planting is critical.



Some techniques that work:


          1)  Large poles (poplar trees)


                   P. fremontii in this case.


                   Use where groundwater is more than 3m deep


                   Holes must be dug or “stinger” used.


                   Ground must support equipment.


                   Drill must go through cobble (not easy).


          2) Drilling to groundwater


                   Drill 18 cm diameter hole.


                   Fill with alluvium.


                   Plant tree in hole.


                   Irrigate from top.


          3)  Irrigating




                   Often will not wet soil deeply enough to induce roots to grow to groundwater.


                   Must carry on for one or two seasons.


Plant more individuals in places likely to have extra available moisture:


          secondary channels




          lower-elevation sites


Problem: trees planted in wetter sites may also be more flood-prone


          Flood energy may disturb vegetation.


          Prolonged inundation may kill trees


          Even phreatophytes can be damaged under prolonged       flooding.


          Fine-grained soils more prone to anaerobiosis.





Channel instability can degrade associated riparian ecosystems two ways.


          1)  Destruction of vegetation through bank erosion.


          2)  Dewatering of riparian zone.


Developing restoration projects along unstable alluvial stream channels.


          Time to implement recovery plans is either 1) before obvious downcutting and erosion have occurred, or          2) after the site has undergone a major erosional event and has begun to stabilize.


General categories of strategies:


          1) revegetation


          2) installation of streambank stabilizing structures.


Planting Locations


          Planting closest to stream results in the greatest chance of loss due to flood disturbance.


          Planting far away from stream results in the greatest chance of vegetation failure due to lack of soil          water.


          Best sites include:


                   1) just downstream of concave stream reaches (accreting areas)


                   2) downstream of large boulders or other obstructions (like logs).


          Plant along an elevational gradient so that there is an optimum elevation range along the planting line.


          Plant vegetation in the geomorphic position it does          best in.


                   Willows go in dynamic landscapes near river channels.


                   Catclaw (Acacia gregii) is drought-tolerant and does well on old stream terraces.


Revegetation offers several advantages over instream structures.


          It is self-maintaining.


          Plants may resist a variety of environmental conditions and flood forces.


          Plants are cheaper.