Models that have been developed are already being used by local, state, and Federal agencies for a variety of purposes, including watershed and ecosystem planning, forestry management, navigation maintenance planning, and water quality compliance evaluations.
The simulation models are classified as follows:
- Hydrologic (Watershed) Models: models that simulate the basin runoff to determine the flood hydrographs resulting from natural or synthetic storms such as HSPF, HEC1, SCS program TR, models from Universities (Texas, Kentucky, Ohio, Stanford, etc.).
- Hydraulic (Hydrodynamic) Models: models that simulate the hydraulics (flows, stages and velocities) in rivers and lakes (1, 2 or 3-D steady or unsteady state). Examples: Corps HEC1 / RAS and 1-D unsteady flow models such as Corps= UNET, programs developed by NWS(Fread), TVA=s program (SOCH), USGS and several other programs developed at universities and private industry; 2-D or 3-D finite difference and finite element models such as Corps TABS, other models from universities (UC, SUNY, UT, Swansea etc.)), Rand Corp. (Lindertse).
- Sediment Transport Models: Models that simulate the processes of erosion and deposition of non-cohesive or cohesive sediments in channels and reservoirs such as Corps HEC-6, QSNET, TABS, etc. Models that determine the total sediment yield from the watersheds such as program developed by Soil Conservation Service, USBR and universities. Many of the existing sediment transport models are stand-alone and some are combined with the hydraulic models for convenient use.
- Contaminant Transport Models: models that simulate the processes of conservative chemical / radioactive / thermal effluent dispersion in channels or lakes. This includes the simulation of adsorption / desorption / decay / erosion / deposition / transportation of contaminated bottom and suspended sediments. These models are generally decoupled from the hydrodynamic models.
Any of the above models with convenient Data Analysis and Graphical Interface Software would be useful tools. Although data requirements for specific or individual models vary depending on their complexity or purpose, it is possible to describe the data requirements in general.
Once a tributary has been identified as a priority with input from the state and other interests, the modeling effort is conducted in three stages:
The first task of this stage is to compile available data and information about the watershed (e.g., land use data, soil characteristics, hydrologic and hydraulic data, etc.). The next task is to establish a watershed team made up of state, tribal, and local agencies and organizations with interest in soil conservation, non-point source pollution prevention, remediation and navigation to help guide model development and application. The Corps uses this input to determine what modeling tools are most appropriate based on the intended uses and user capabilities. A scoping report is then prepared which describes the proposed model development and technology transfer. In general, the scoping stage is completed in less than a year.
- Model Development
In most cases, this program has applied existing models or has used “off the shelf” modeling tools that have been developed by the Corps’ district office or its contractors. Where local universities or other federal agencies have existing models that may be utilized, the Corps has provided funding to these organizations to build on existing tools. In some cases, proprietary models have been used in the past; however, this method is not preferred. This program has not been used for research or the development of entirely new modeling tools. As directed by the authorizing legislation, tributary modeling tools must be developed using existing information. This phase of the project is generally completed in a timeframe of one to two years.
- Technology Transfer
After a modeling tool has been developed, the Corps holds a technology transfer workshop to provide training to stakeholders from the watershed. Participants are provided the modeling software and user information at no cost. For each tributary, a final report is developed to document modeling activities and information on the watershed obtained through this effort. These technology transfer workshops also facilitate a dialogue on resource issues among diverse groups and, in some cases, foster new partnerships.
- Detailed watershed maps: USGS/Soil Conservation Service/FEMA Flood Insurance Maps / State DNR / Local Agencies;
- Land use data (agricultural, grass land, parks, forest, ponds / streams, roadways, residential, urban, industrial, etc.) from above sources including county / city / village maps increasing usage of GIS by more townships;
- Data related to land slopes, township drainage patterns, sedimentation ponds and outfall locations and data maintained by sewage and water treatment plants;
- Weather data (precipitation and temperature) for specific storms (NWS and other local agency gages);
- Stream gauge data for the period-of-record (USGS, NWS, Corps of Engineers);
- Cross sections of stream, bed slope and flood plain features — at a minimum, we need to capture reasonably good estimates of channel stage versus storage;
- Environmental assessment / impact statement reports related to highways and other construction projects;
- Data from any agriculture/irrigation experiment stations;
- Hydrologic reports (from state/local agencies / universities / A&E firms) related to the project area or similar watersheds in the area to be able to utilize data such as calibrated watershed parameters and flood flow simulations.
- Existing stream data related to cross sections, channel reach bed slopes, bridges / culverts / weirs and channel reach roughness, new cross sectional data, if needed, and flood plain features;
- Computed flood hydrographs for specific and synthetic storms from a hydrologic model such as HSPF or HEC1 or Soil Conservation Service watershed model etc.;
- Local inflows and municipal / industrial withdrawals and discharges from and to the stream;
- The data source for the above may be available from previous hydrologic / hydraulic / environmental reports; if not readily available they will have to be developed from results of a hydrologic model.
Sediment Transport Model:
- Data Sources – USGS / SCS / USEPA / State DNR;
- Previous investigations and measurements for the stream in question (or similar one in the area) to obtain estimates of suspended sediment concentrations for a range of flood flows including data related to sediment classification and gradation;
- Most importantly, estimates of sediment yield from the watershed in question or similar watersheds in the area;
- Additional sediment survey data from bed load/suspended load samplers;
- Laboratory data related to critical shear stress for sediment materials of interest (from literature);
- Input data required by hydrologic / hydraulic models related to channel geometry, reach slopes, roughness etc as described above;
- Output from hydrologic / hydraulic models such as flood hydrographs / velocities / stages.
Contaminant Transport Model:
- This model would require the identification of the chemical species, dispersivity coefficients (or approximate dispersion coefficients), sediment adsorption coefficients and the output from hydraulic model in the form of velocity field. The dimensionality of the model is expected to be the same as the hydrodynamic model.