Technical Service Center
Sedimentation and River Hydraulics Group
SIAM Methods
The algorithms define a series of sediment linkages between the reaches within a watershed and evaluate supply of material to a reach compared with the transport capacity according to transport mode. SIAM identifies sediment yeilds, areas of potential instablity, and potential remedies. SIAM differs from mobile boundary modeling by tracking sources of material to identify causality, performing a trend analysis rather than a state evolution, and using geomorphic principles for predicting change rather than routing material.
SIAM Local Accouting Conceptual Framework
The basic premise of the model is that movement of bed material load (sediment in transport that is found in significant quantities in the bed) is limited by the capacity of the flow to transport sediment, while movement of wash load (sediment in transport that is not found in significant quantities in the bed) is supply limited. Changes in one part of the watershed can impact areas spatially removed. Results identify areas of short and long term instability and provide information on the quantity and source of sediment loads in selected reaches of the fluvial system.
SIAM provides an intermediate level of analysis more quantitative than a conventional geomorphic evaluation or fluvial audit, but less specific than a numerical, mobile-boundary simulation. The quick setup and run times provide the opportunity to run many simulations to explore operational scenarios, perform sensitivity studies, and create risk analysis information. David Mooney developed SIAM at Colorado State University for the U. S. Army Corps of Engineers under the Regional Sediment Management program (http://www.wes.army.mil/rsm) and is continuing development at the Bureau of Reclamation.
SIAM is unique in its ability to perform a quantitative analysis on large networks of nested tributaries, track individual sediment sources to the impact on the channel structure, rapidly setup and compute simulations, and provide prescriptions to address problems. The HEC-RAS modeling software is scheduled to include SIAM in future releases as a hydraulic design module.
Processes Modeled
- Short term channel instability
- Long term potential for channel instability
- Source to impact sediment tracking
- Separate wash material and bed material transport processes
- Linkages between networks of nested tributaries
- Steady and unsteady flow regimes
- Sand, gravel, and cohesive channels
- Armored or paved channels
Processes Ignored
- Adjustment time frames
- Intermediate evolutionary stages
- Ultimate channel state
- Change in bed material composition (armoring or fining)
- Changes not associated with sediment imbalances
- Floodplain interactions
- Local adjustments at the pool-riffle scale
Model Input
- Substrate Composition
- Hydrologic Regime
- Hydraulic Characteristics
- Sediment Transport Relationship
- Sediment Sources
Model Output
- Sediment yields
- Sediment balances
- Location and relative influence of agents causing instability
- Management solution strategies
- Stable channel design criteria
Potential Use of Output Results
- Sediment yield management plans
- Stream profile stability analysis and design
- Component relative impact analysis (significance of watershed features)
- Stochastic risk and uncertainty analysis (sensitivity)
- Project scoping or preliminary planning
- Rehabilitation design
- Input development for more detailed studies
Version
The model is currently in Beta testing.
Contact David Mooney at (303) 445-2552 for availability and more information.