Numerical Simulation of a Dam-Break Flood Wave V. Bellos1 and V. Known DAMBRK software and its replacement FLDWAV should also be mentioned. Apr 14, 2009 Before downloading any software from this. Please contact in the International Activities Office. It is also strongly. DAMBRK SMPBRK NETWORK. The final analysis is done using the software BOSS DAMBRK for evaluating the extent of inundation, travel time and velocity of downstream progressing water.
DAMBRK (A Dam-Break Flood Forecasting Model) VERSION/DATE: 6/20/88. Please Note: FLDWAV is the replacement for this program. OPERATING SYSTEM: DOS DISTRIBUTOR: NWS (National Weather Service, NOAA) DOCUMENTATION (559 Pages): THE NWS DAMBRK MODEL: THEORETICAL BACKGROUND/USER DOCUMENTATION By D.L. Fread, Hydrologic Research Laboratory, Office of Hydrology, National Weather Service (NWS) June 20, 1988 (Reprinted October 1988) ADDITIONAL PROGRAMS In addition to DAMBRK '88, the following models are included with program installation and documentation: SMPDBK - Version 9/91 - an interactive simplified dam-break model which computes the peak discharge, water surface elevation, and time of occurrence for selected cross sections downstream of a breached dam (more information below). BREACH - Version 7/88 - a deterministic model of the erosionformed breach (overtopping or piping initiated) in an earthen dam (man-made or landslide-formed); it computes the outflow hydrograph and the breach parameters used in DAMBRK and SMPDBK (more information below).
DWOPER - Enhanced Network Version 7/18/84 (latest revision 8/89) - an unsteady flow dynamic routing model (one-dimensional Saint-Venant equations) for a single channel or network (dendritic and/or bifurcated) of channels for free surface or pressurized flow (more information below). CROSS-SECTION - plots topwidth-elevation from cross-section data in x-y coordinates; also computes distance weighted average cross sections; also converts HEC 'GR' cards to the correct NWS Format. DAMBRK: ABSTRACT A dam-break flood forecasting model (DAMBRK) is described and applied to two actual dam-break flood waves. The model consists of a breach component which utilizes simple parameters to provide a temporal and geometrical description of the breach. The model computes the reservoir outflow hydrograph resulting from the breach via a broad-crested weir flow approximation, which includes effects of submergence from downstream tailwater depths and corrections for approach velocities. Also, the effects of storage depletion and upstream inflows on the computed outflow hydrograph are accounted for through storage routing within the reservoir.
The basic component of the DAMBRK model is a dynamic routing technique for determining the modifications to the dambreak flood wave as it advances through the downstream valley, including its travel time and resulting water surface elevations. The dynamic routing component is based on a weighted four-point, nonlinear finite-difference solution of the one- dimensional equations of unsteady flow (Saint-Venant equations) which allows variable time and distance steps to be used in the solution procedure. Provisions are included for routing supercritical flows, subcritical flows, or a spontaneous mixture of each, and incorporating the effects of downstream obstructions such as road-bridge embankments and/or other dams, routing mud/debris flows, pressurized flow, landslide-generated reservoir waves, accounting for volume and flow losses during the routing of the dambreak wave, considering the effects of off-channel (dead storage), floodplains, and floodplain compartments.
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Model input/output may be in either English or metric units. Modeling difficulties and parameter uncertainties are described and methods of treating them are discussed.
Model data requirements are flexible, allowing minimal data input when it is not available while permitting extensive data to be used when appropriate. The model was tested on the Teton Dam failure and the Buffalo Creek coal-waste dam collapse. Computed outflow volumes through the breaches coincided with the observed values in magnitude and timing. Observed peak discharges along the downstream valleys were satisfactorily reproduced by the model even though the flood waves were severely attenuated as they advanced downstream. The computed peak flood elevations were within an average of 1.9 ft and 2.1 ft of the observed maximum elevations for Teton and Buffalo Creek, respectively. Both the Teton and Buffalo Creek simulations indicated an important lack of sensitivity of downstream discharge to errors in the forecast of the breach size and timing. Such errors produced significant differences in the peak discharge in the vicinity of the dams; however, the differences were rapidly reduced as the waves advanced downstream.
Computational requirements of the model are quite feasible for mainframe, mini- or microcomputers. Suggested ways for using the DAMBRK model in preparation of pre-computed flood information and in real-time forecasting are presented along with several examples illustrating the use of the DAMBRK model. DAMBRK: INTRODUCTION Dams provide society with essential benefits such as water supply, flood control, recreation, hydropower, and irrigation. However, catastrophic flooding occurs when a dam fails and the impounded water escapes through the breach into the downstream valley. Usually, the magnitude of the flow greatly exceeds all previous floods and the response time available for warning is much shorter than for precipitation-runoff floods. According to reports by the international Commission on Large Dams (ICOLD, 1973) and the United States Committee on Large Dams in cooperation with the American Society of Civil Engineers (ASCE/USCOLD, 1975), about 38% of all dam failures are caused by overtopping of the dam due to inadequate spillway capacity and by spillways being washed out during large inflows to the reservoir from heavy precipitation runoff. About 33% of dam failures are caused by seepage or piping through the dam or along internal conduits, while about 23% of the failures are associated with foundation problems, and the remaining failures are due to slope embankment slides, damage or liquefaction of earthen dams from earthquakes, and landslide-generated waves within the reservoir.
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Middlebrooks (1952) describes earthen dam failures that occurred with the U.S. Prior to 1951.
Johnson and Illes (1976) summarize 300 dam failures throughout the world. The potential for catastrophic flooding due to a dam failure was brought to the Nation's attention during the 1970's by several floods due to dam failures such as the Buffalo Creek coal-waste dam, the Teton Dam, the Toccoa Dam, and the Laurel Run Dam. Also, there are many dams that are 30 or more years old, and many of the older dams are a matter of serious concern because of increased hazard potential due to downstream development and increased risk of failure due to structural. Deterioration or inadequate spillway capacity. A report by the U.S. Army (1981) gives an inventory of the Nation's approximately 70,000 dams with heights greater than 25 ft or storage volumes in excess of 50 acre-ft. The report also classifies some 20,000 of these as being 'so located that failure of the dam could result in loss of human life and appreciable property damage.'
Dambrk Software
The National Weather Service (NWS) has the responsibility to advise the public of downstream flooding when there is a failure of a dam. Although this type of food has many similarities to floods produced by precipitation runoff, the dam-break flood has some very important differences which make it difficult to analyze with the common techniques which have worked so well for the precipitation-runoff floods. To aid NWS flash flood hydrologists who are called upon to forecast the downstream flooding (flood inundation information and warning times) resulting from dam-failures, a numerical model (DAMBRK) has been developed. The DAMBRK model may also be used for a multitude of purposes by engineering planners, designers, and analysts who are concerned with possible future flood inundation mapping due to dam-break floods and/or reservoir spillway floods. The DAMBRK model can also be used for routing any specified flood hydrograph through reservoirs, rivers, canals, or estuaries as part of general engineering studies of waterways. Its principal limitation is its confinement to analyzing flow through a single waterway rather than a network of mutually interactive channels, e.g., dendritic (tree-type network of rivers, distributary network of irrigation canals, and estuarial network of waterways. Two other NWS models may be used for channel networks, DWOPER (Fread, 1978, 1983), and FLDWAV (Fread, 1985b; Fread and Lewis, 1988).
The models are available for mainframe, mini- or microcomputers. The FLDWAV model is scheduled for release sometime during the latter part of 1988. Model Development The DAMBRK model represents the current state-of-the-art in understanding of dam failures and the utilization of hydrodynamic theory to predict the dam-break wave formation and downstream progression.
The model has wide applicability; it can function with various levels of input data ranging from rough estimates to complete data specification; the required data is readily accessible; and it is economically feasible to use, i.e., it requires minimal computational effort on mainframe computing facilities and is feasible for use on microcomputers (IBM PC compatibles). DAMBRK is used by most fedral/state agencies in the U.S. And in over forty nations around the world. It is also extensively used by private consultants, hydropower and mining companies, and is utilized in more than 40 universities for teaching and research purposes.