VICKSBURG, Miss.— Utilizing their combined decades of experience in river mechanics, a four-member team of research physicists and hydraulic engineers with the Engineer Research and Development Center (ERDC) combined their expertise to invent the Integrated Section, Surface Difference Over Time, version 2 (ISSDOTv2) method, which accurately measures the sediment moving on the bed of large sand-bed rivers. The team from ERDC’s Coastal and Hydraulics Laboratory (CHL) received their patent, “Bedload transport methodology and method of use,” in July of 2021.
The initial research work to develop and validate the functional relationships was completed by David Abraham as part of a doctoral dissertation in 2008. Subsequently, CHL employees Tate McAlpin, Thad Pratt and John Shelley all made significant contributions to the methodology.
“Without these contributions, the method might have just ended up on a dusty shelf of PhD dissertations,” Abraham said.
Answering this river engineering challenge, the new method estimates an overall bed-load transport rate by measuring bathymetric elevations multiple times in a specific area. It computes volumetric surface differences for incremental time steps related to erosion and/or deposition rates. An equation was developed that relates the incremental scour or deposition rates to the average transport of a moving sand wave, thereby providing an estimate of the sand moving on the bed of the river.
“The method is for anyone who needs to know how much sediment (usually sand) is moving in bed-forms (sand waves) on the bottom of large sand-bed rivers,” McAlpin said. “So, first and foremost, that would be river managers who are responsible for keeping the navigation channels open.”
McAlpin added it will also benefit geomorphologists, wildlife ecologists, sand miners, lock and dam and port operators and even private marina operators.
Invention Uses and Advantages
The U.S. Army Corps of Engineers (USACE) river managers no longer view sands moving in river-beds as a nuisance or problem related to dredging requirements. Instead, these sands are proving to be an important element as river engineers and managers are now asked to allocate bed-sediment resources for a variety of competing purposes and interests.
“For river managers to make involved decisions, they must have some idea of how much sediment is moving on the bed of a river,” McAlpin explained. “This invention provides a much-needed quantitative management tool for those tasked with allocating a river's sand resources.”
Through the use of this method, USACE can address critical issues, such as land-building in the Louisiana Coastal Areas (LCA) and commercial sand mining in many locations throughout the country. For environmental concerns related to the Endangered Species Act (ESA) and Environmental Impact Statements (EIS), USACE managers must evaluate sands’ availabilities.
Such evaluations reveal ecological habitat river features and also ensure adequate draft depths in navigation channels to meet lock and dam navigation requirements.
“Recent applications of this patented method in support of districts included bed-load transport measurements to develop bed-load rating curves and sediment budgets,” McAlpin said. “This is important for quantifying the amount of sediment entering/leaving/accumulating in an area. It has also been utilized to evaluate the habitat suitability (or lack thereof) for endangered species. Numerical modeling of sediment transport processes is becoming more and more prevalent, and these bed-load transport measurements can be utilized to validate these numerical models.”
This invention was developed in cooperation with the University of Iowa and the USDA-ARS National Sedimentation Lab. Tests were conducted at the National Sedimentation Laboratory in Oxford, Mississippi.
“The team determined an incremental amount of movement between two mapped surfaces could be utilized to quantify the bed-load moving on large rivers. The measured 3-D scour and deposition volumes from the difference of the two measured surfaces and the time between those two measurements allowed for the computation of a volumetric transport rate,” McAlpin said. “The transport values for each swath of data are combined to get the total bed-load for the whole river cross section. Numerous examples of its current usage include numerical model validation, bed-load rating curve and sediment budget development.”
He added that there are possible uses for the method in support of the military in terms of access/denial associated with river bed-forms limiting draft clearance.
“Now, Corps districts have a dependable way to measure the quantity of sand moving in the dunes on the bottom of large sand-bed rivers,” McAlpin said. “To date, 10 Corps districts have used the method for the various purposes mentioned above with total funding exceeding four million dollars.”
Link to patent application: https://uspto.report/patent/grant/11,067,475