Dam-Breach Modelling For Lane City Reservoir, USA
- Alastair Sheppard
- Oct 11, 2023
- 3 min read
Updated: Mar 13
What our customers say:
“The Lane City Reservoir project provided an opportunity to leverage the software’s integrated 1D and 2D solvers, particularly the 2D TVD solver, which is specifically developed to model "shock" waves produced by rapid flow from a dam breach.”
Flood Modeller's 1D and 2D solvers were used to perform dam-breach modelling for the Lane City Reservoir dam, confirming its hazard classification and developing dam-failure inundation maps for an Emergency Action Plan. Lane City Reservoir, a proposed off-channel reservoir owned and operated by the Lower Colorado River Authority, will feature existing and proposed conveyance facilities, including pump stations, canals, and a river outlet, to move water in and out of the reservoir.
The project site, which is relatively flat, will be encircled by a 45-feet-high embankment dam on all four sides, enclosing nearly 1,100 acres of farmland to store 40,000 ac-ft of water. By optimising reservoir operations, the Lower Colorado River Authority projects that the new reservoir will add 90,000 ac-ft of firm water supply.
During the design phase, dam-breach modelling using Flood Modeller to confirm the dam's hazard classification and develop dam-failure inundation maps for an Emergency Action Plan. The flat terrain required modelling a variety of split flow paths and complex hydraulic interactions between multiple watersheds, channels, and floodplains. Dam-failure floods were also modelled for breaches on each side of the rectangular ring embankment using a 1D-2D linked model.
Flood Modeller was chosen for its range of tools that help avoid model instabilities in complex hydrodynamic dam-failure models. The Lane City Reservoir project provided an opportunity to leverage the software’s integrated 1D and 2D solvers, particularly the 2D TVD solver, which is specifically developed to model "shock" waves produced by rapid flow from a dam breach. This solver allows for more accurate calculations of the complex hydraulics of steep changes in velocity and water level, providing increased stability compared to other 2D solvers. This feature is especially important for modelling a dam breach flood wave across the flat terrain surrounding Lane City Reservoir.
Key Facts
Successful dam-breach modelling: Assessed the hazard classification of the dam effectively.
Comprehensive inundation maps: Developed for an Emergency Action Plan.
Enhanced accuracy: Flood Modeller’s 2D TVD solver provided precise calculations of changes in velocity and water levels.
Streamlined workflow: Flood Modeller’s HEC-RAS import tool facilitated automatic import of existing data.
Using Flood Modeller, 1D model components were utilised to represent discharge through the dam breach and flows within the Colorado River, while 2D model components depicted flow across overland areas east and west of the Colorado River, including its floodplains and the adjacent eastern watershed.
The complex interactions between flow areas were effectively represented by linking the 1D and 2D model components. This integration allowed the 1D breach model to be influenced by 2D tailwater effects, and 2D overland flow on both sides of the Colorado River to be influenced by the 1D elevations within the Colorado River channel. Each model seamlessly passed flows to the connecting models, dynamically responding to adjacent water depths and flows.
The 1D Flood Modeller model of the Colorado River channel was developed by importing cross sections and other data from two existing, sequential 1D HEC-RAS models of the Colorado River. The HEC-RAS importer tool within Flood Modeller enabled direct import of cross-section data from HEC-RAS, eliminating the need for manual conversion.
The first model began well upstream of Lane City Reservoir and extended downstream to Bay City. The second model started at Bay City and extended to the Gulf Coast. The first model used results from the second model as a downstream boundary condition, allowing the two models to be readily linked together without affecting their hydraulic performance.
The 2D models were developed using digital elevation models with a combined spatial domain covering over 300 square miles. Although the finest digital elevation models were available with a 3m grid size, a coarser resolution was selected for modelling most areas.
