Technical Papers
The following technical papers on the FLO-2D Model and project applications were published or presented at conferences:
Modeling Tsunami Waves and Ocean Storm Surges with FLO-2D®
O’Brien, J. S.
Presented at: 2005 American Water Resources Association, 2005 Summer Specialty Conference, Institutions for Sustainable Watershed Management, Honolulu, Hawaii.
Abstract: Overland floodwave progression of ocean storm surges from hurricanes and fast rising tsunami waves can be simulated with the FLO-2D® two-dimensional flood routing model. Ocean surge flooding can be simulated by assigning water surface stage and duration to the coastline grid elements. FLO-2D® is a volume conservation model that is effective for analyzing riverine or unconfined alluvial fan flooding, but it can also simulate storm surges through coastal urban areas with detailed resolution. Various ocean storm surges were simulated for the City of Waikiki, Oahu, Hawaii using an existing FLO-2D® watershed model. The results illustrate that the area of inundation is a function of both wave height and duration as they progress through the downtown Waikiki area and into the Ala Wai Canal that bisects the city.
Hazard Zone Delineation for Urbanized Alluvial Fans
R. García, J.J. Rodríguez and J.S. O’Brien
Presented at: 2004 ASCE World Water & Environmental Resources Congress – Arid Lands Symposium, Salt Lake City, Utah.
Abstract: A method is proposed to delineate hazard maps for flooding and mud and debris flow events, based on the application of a two-dimensional flood routing model FLO-2D. The method defines hazard levels based on flood event frequency and intensity. The FLO-2D model has been enhanced with pre- and post-processor programs to automate data input and to generate hazard maps in ArcView GIS format. The proposed methodology was tested in twenty three sites in the Caracas and Vargas State region in Venezuela. This paper describes one application of the proposed method to the community of Tanaguarena on the Cerro Grande alluvial fan. The model results compare very well to the maximum flow depths and area of inundation observed during the December 1999 Vargas debris flow disaster. The hazard maps for the region are being used by local agencies to develop emergency plans and new land use policies. The methodology is being expanded to other flood hazard regions in Latin America.
Real Time Rainfall-Runoff Modeling on Alluvial Fans , Floodplains and Watersheds
J. S. O’Brien and Bing Zhao
Presented at: 2004 ASCE World Water & Environmental Resources Congress – Arid Lands Symposium, Salt Lake City, Utah.
Abstract: Real time rainfall runoff modeling is rapidly advancing and soon will be the framework of a predictive early flood warning system. The Flood Control District of Maricopa County has supported the development of spatially and temporally variable rainfall simulation in the FLO-2D model. FLO-2D is a two-dimensional flood routing model that can simulate rainfall- runoff. Initially, FLO-2D was designed to simulate uniform rainfall on a finite difference grid system of a watershed or floodplain. The model system has been expanded to interpolate ASCII grid file rain data (such as NEXRAD rain data or the Maricopa County rain gage data) to incorporate spatially and temporally variable rainfall data. FLO-2D can also simulate a moving storm system. The variable rainfall-runoff can be simulated with multiple inflow flood hydrographs routed over urbanized alluvial fans and floodplains. Spatially variable rainfall losses are computed with the Green-Ampt model. The assignment of the Green-Ampt parameters are automatically generated by a processor program. Simulating spatially and temporally variable rainfall enables monitored rain storms to be replicated, design storms to be predicted, or real-time network rain gages data to be simulated as a projected flood event. The new rainfall components in the FLO-2D flood routing model set the stage for integration for a predictive early flood warning system.
Reasonable Assumptions in Routing a Dam Break Mudflow
J. S. O’Brien
Presented at: 2003 Third International Conference on Mud and Debris Flows, Proceedings of Debris Flow Hazards Mitigation: Mechanics, Prediction, and Assessment, Davos, Switzerland, Rickenmann & Chen, eds., Millpress, Rotterdam, V. 1.
Abstract: An active landslide threatens to dam the North Fork Cache Creek in Northern California. Releases from an upstream reservoir would result in overtopping and breaching the landslide dam resulting in a mudflow or mudflow. The FLO-2D model is applied to route the landslide dam breach mudflow and map the hazard area of inundation. Two dam landslide scenarios are analyzed. One scenario has a peak discharge in excess of 1 million cfs. By making reasonable assumptions regarding dam breach parameters, sediment concentration and mudflow fluid properties, the potential mudflow hazard can be mapped.
Simulation of Flooding and Debris Flows in the Cerro Grande River
Maria E. Bello, J.S. O´Brien, J.L. López , and R. Garcia-Martínez
Presented at: 2003 Third International Conference on Mud and Debris Flows, Proceedings of Debris Flow Hazards Mitigation: Mechanics, Prediction, and Assessment, Davos, Switzerland, Rickenmann & Chen, eds., Millpress, Rotterdam, V. 1.
Abstract: The December 1999 3-day storm along the north-central coast of Venezuela initiated widespread landslides that evolved into mud and debris flows in watersheds throughout the coastal State of Vargas. One of the many urbanized alluvial fans impacted by flooding and debris flows was the community of Tanaguarena at the mouth of the Cerro Grande River canyon. The Institute of Fluid Mechanics, University of Central Venezuela, is currently designing flood and debris flow mitigation on this alluvial fan. A three-phase analysis of the replicating the 1999 flood was implemented. First, the December 1999 rainfall distribution, intensity and runoff were investigated. Then the 3-day flood hydrograph was estimated with the HEC-1 hydrologic. Finally, a two-dimensional flood routing model FLO-2D with the capabilities of simulating hyperconcentrated sediment flows was applied to route the flows over the alluvial fan. With this calibrated model, flood mitigation can be designed for a selected frequency design flood event. Results indicate that the FLO-2D model can accurately replicate the 1999 flooding on the Cerro Grande fan.
A Case Study of 2-Dimensional Modeling in an Urban Environment
W.S. Ogden and J.S. O’Brien
Presented at: 2001 3rd International Symposium on Environmental Hydraulics, IAHR, Arizona State Univ., Tempe, Arizona.
Abstract: Floodplain development presents many challenges to the floodplain manager and hydraulic engineer. Historic floodplain maps that were created when little or no development existed are no longer valid representations of the existing floodplain condition. Conveyance of floodwaters in wash corridors and arroyo floodplains that were once predominantly overland sheet flow or flow in rills and gullies, are now redirected by houses, fences, small buildings, streets, and other obstructions to flow. In many of these cases, flood containment within the historic mapped flood plain is questionable due to loss of storage and flow path obstruction, and there is a need to quantify the discharge that has been diverted from the floodplain. Traditional one-dimensional backwater models are inadequate to predict the unconfined flow behavior in such urban environments and if used, require too many assumptions regarding flow diversions and potential confinement. Advances in the computational speed of computers has facilitated the reality of using two-dimensional flood routing programs to efficiently simulate these complex urban flood environments with accuracy and detail.