Effects of relict levees on sediment and debris deposition in delta systems

From Salish Sea Wiki
Jump to: navigation, search


Recent Topic Edits

Salish Sea References

Wiki Rules

  • Wiki text does not reflect the policy or opinion of any agency or organization
  • Please adhere to our social contract
  • Complain here, and be nice.


Link to List of Workgroups Link to List of Efforts Link to List of Resources Link to List of Documents Link to List of Topics Link to List of Places

Link to Headwater Sites Link to Lowland Watershed Sites Link to Floodplain Sites Link to Delta Sites Link to Embayment Sites Link to Beach Sites Link to Rocky Headland Sites

Relic levees and dikes not removed during restoration reduce water flow over the marsh face, reducing the input of sedimentparticles of clay, silt, sand, gravel, or cobble, transported by water, are called sediment. laden flood waters and reducing sedimentparticles of clay, silt, sand, gravel, or cobble, transported by water, are called sediment. deposition rates.

Notes

  • Sheet flow over the delta plain has been proposed as a significant pathway for sedimentparticles of clay, silt, sand, gravel, or cobble, transported by water, are called sediment. deposition, given that most sedimentparticles of clay, silt, sand, gravel, or cobble, transported by water, are called sediment. is transported during flood flow and delta plain vegetation slows velocity and increases deposition.
  • The formation of natural levees may mimic the function of anthropogenic levees at all but high tidal flows.
  • Sediment supply issues may be most significant on sites where there is a sedimentparticles of clay, silt, sand, gravel, or cobble, transported by water, are called sediment. shortage due to impoundment behind dams (See Nisqually Refuge Restoration)
  • Deposition regime is different between bed-load and suspended-load, with bed load being most significant during island formation, and suspended load during island accretion under vegetation (Eilers 1974).
  • Distributary configuration effects on delta sediment deposition is a related topic, where the general distribution of sedimentparticles of clay, silt, sand, gravel, or cobble, transported by water, are called sediment. is controlled by larger scale delta routing, while smaller scale deposition may be affected by remnant dikes.
  • There is some evidence in the Skagit Delta that remnant levees and dikes affect wood accumulation which in turn affects the viability of assisted vs. unassisted development of tidal fresh swamp (Hood 2007).

Delta Strategy Analysis

ESRPDeltaStrategy.PNG

The uncertainties in how this topic affects delta restoration has resulted in its inclusion in the ESRP River Delta Adaptive Management Strategy. This three criteria analysis should build off the analysis above, and supports development of learning projects.


Importance Viability Policy Relevance

Restoration in subsided deltas depends on deposition to recovery functions. Suspended load is transported during high river flow. Out-of-channel movement of river water over the vegetated face of a restored site during high river flow events would logically increase deposition rate.

A wide range of factors may interact with a variety of structures affecting sedimentparticles of clay, silt, sand, gravel, or cobble, transported by water, are called sediment. input to a site. The ability to predict these dynamics are likely subsidiary to questions of system scale sedimentparticles of clay, silt, sand, gravel, or cobble, transported by water, are called sediment. supply and routing.

The significant decision of how much levee or dike infrastructure to leave behind, how to configure these remnants, interest in recreational access all figure heavily into design decisionmaking, and would be strongly influenced by additional evidence.