Installing Erosion Control Structures across a Landscape as a Restoration Treatment and Adaptive Watershed Management Alternative for Climate Change

Project ID: 720
Principal Investigator: Deborah Tosline
Research Topic: Sediment Management and River Restoration
Funded Fiscal Years: 2016
Keywords: None

Research Question

Grassroots efforts in Arizona are underway to install Erosion Control Structures (ECS) to reduce channel cutting,
promote river and habitat restoration, increase and extend surface water flows, recharge shallow groundwater
systems, and reduce sediment loads in flood flows prior to storm flows discharging from the watershed.
Valer and Josiah Austin, property owners who installed thousands of ECSs, realized remarkable river and habitat
restoration. Anecdotal evidence shows that use of ECSs dramatically increases the availability of water and
supports ecosystems. The Sky Island Restoration Cooperative (SIRC) began in 2014 in southeastern Arizona as a
bi-national collaboration of government and non-governmental organizations, private landowners, ranchers,
students, volunteers, scientists, and restoration practitioners developing inter-disciplinary and cross-jurisdictional
ECS projects. Proponents seek to install ECS's across watersheds.
To evaluate potential impacts on surface water rights, the US Geological Survey (USGS) studied a tributary with
over 2,000 ECSs that were installed three decades ago. The results show that peak flood flows are reduced,
surface water flow duration is extended, and surface water flow volumes increase. Potential research questions for
a conducting proposal will be refined during the scoping proposal and include:
-How do Erosion Control Structures (ECS) impact storm flow volumes and surface water supplies and rights?
-How do ECSs impact shallow groundwater supplies?
-What is the impact of ECSs on habitat restoration?
-How do ECS systems change stream morphology and sediment transport?
-How does the effect scale with size and number of structures?
-What are the downstream effects of ECS systems?
-Can ECSs be constructed to mimic natural logjams or beaver dams?
-Is it possible to construct a semi-permanent ECS that encourages establishment of a self-sustaining population
of beaver to maintain system functionality?

Need and Benefit

Degradation of river habitats in arid western states prompted private land owners to install ECSs in drainages
resulting in dramatic improvements in habitat and availability of water. Landscape scale ECS installations have
been shown to stop gully headcutting, channel bed lowering, loss of habitat and to increase surface water flows.
Land managers in southeastern Arizona embrace ECS systems as a restoration tool. Hydrologic research data is
sparse due to lack of instrumentation and monitoring.
Climate change predictions include dryer/wetter precipitation events with fewer moderate events. Adaptive
management alternatives are necessary to mitigate the impacts of intense precipitation events, reduce
sedimentation, flood flow peaks, and erosion. USGS data, collected during the 2014 summer monsoon season,
compared a treated drainage with an untreated drainage (control). Results showed that storm flow in the treated
drainage was less flashy, had fewer transmission losses, and showed a reduction in the average rate of flow by
more than one half, primarily in the size and duration of peak flow. If ECS systems function as observed, they
would reduce hazardous flood flow peaks.
ECS systems consist of sandy soils with high infiltration capacities that deposit on the upstream side of an ECS
increasing the capacity to detain water. ECS systems increase shallow groundwater storage allowing for slow and
controlled release of water. USGS results showed that the treated channel sustained about 28% more surface flow
volume per unit area than the untreated channel. The runoff ratio of the treated drainage increased over time to
more than double the measurements made in the untreated drainage. Results indicate that installation of ECS
systems would not reduce downstream storm flows and would make water available for the environment.
About 10 percent of Arizona's riparian habitat remains. ECS installations in Mexico reportedly restored more than
one mile of perennial flow. The USGS concluded that ECS installations increase aridland baseflow resulting in more
water available to the environment. If ECS systems function as reported, they would increase ecologic corridors
and reduce habitat fragmentation.
In the arid southwest, mountain front recharge replenishes aquifers. Slowed storm flows in mountain front
tributaries would increase groundwater recharge. Stream flow and groundwater data are required to further
evaluate the hydrologic impacts of ECS installation and to promote conjunctive management of surface water and
groundwater resources.
Results from USGS sediment modeling (no field measurements) indicate that 800 tons/year are eroded in Turkey
Pen. It is estimated that 400 tons/year get yielded and that 200 tons/year would be captured in the ECS system. If
ECS systems are feasible, treatment would reduce sediment loads in tributaries that discharge to Reclamation
reservoirs. Watershed wide ECS installations would significantly reduce sediment loads, flood hazards, and
post-storm maintenance. The Arizona Department of Environmental Quality would like to reduce sediment loads
in flood flows to improve river water quality.
Research is needed to guide site selection and ECS sizing to prevent downstream impacts on channel processes.
Large scale building of grade control structures can cause channel incision downstream of the structures. Results
of research would be used to develop guidelines describing appropriate watershed applications and channel
context for the structures.
It may be possible to design a temporary ECS that is designed to increase base flows long enough for riparian
vegetation to become established. The establishment of thick riparian vegetation can provide a source of woody
debris that can serve similar functions as the ECS. In addition, it could encourage the establishment of a
self-sustaining beaver population that would then create a self-sustaining ECS.

Contributing Partners

Contact the Principal Investigator for information about partners.

Research Products

Bureau of Reclamation Review

The following documents were reviewed by experts in fields relating to this project's study and findings. The results were determined to be achieved using valid means.

Installing Erosion Control Structures across a Landscape as a Restoration Treatment and Adaptive Watershed Management Alternative for Climate Change (final, PDF, 1.2MB)
By Deborah Tosline
Publication completed on September 30, 2016

The study assessed the potential to develop partnerships, identify research locations, and develop a refined scope of work to conduct hydrologic research at Erosion Control Structure (ECS) installations. Anecdotal evidence indicates that ECS installations result in dramatic environmental improvements including: habitat establishment, maintenance, and inter-connectivity; reductions in stormflow bedload; reduced storm flow peaks; longer flow durations; increased availability of local water resources; and increased environmental awareness, education and economic opportunities. Climate change projections predict fewer yet more intense precipitation events. Adaptive watershed management alternatives may be used to manage and mitigate flood flows during intense storms. USGS research shows that ECS-treated drainages had fewer transmission losses, and showed a reduction in average rate of flow, primarily in the peak flow size and duration, by more than one half, but research indicates a lack of data to quantify ECS impacts. The study gained over 90 participants, developed cooperative collaborations with partners and stakeholders, identified research sites, developed a scope of work, and prepared a proposal to collect pre- and post-installation hydrologic data at ECS research sites.

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Last Updated: 4/4/17