NWS FLDWAV Model: The Replacement of DAMBRK for Dam-Break Flood Prediction

The NWS DAMBRK model, which has been used by the National Weather Service (NWS) and many in the general engineering community since the late 1970’s for predicting the flooding from an actual or hypothetical dam failure, is scheduled for replacement by the FLDWAV model. The FLDWAV model has been undergoing development and testing intermittently for several years (Fread and Lewis, 1988) within the NWS Hydrologic Research Laboratory. It is planned to be released during the fall of 1993 to a few selected users within NWS and outside the agency for additional testing of the model. A general release of the FLDWAV model is scheduled for the summer of 1994. FLDWAV, like DAMBRK, computes the outflow hydrography from a dam due to spillway, overtopping, and/or dam-breach outflows. The resulting floodwave is then routed through the downstream channel/valley using an implicit finite-difference numerical solution of the complete Saint-Venant equations of one-dimensional unsteady flow, along with appropriate internal boundary equations representing downstream dams, bridges, weirs, waterfalls, and other man-made natural flow controls. The flow may be “mixed” (subcritical and/or super-critical) throughout the downstream routing reach, and the flow may vary from Newtonian (water) to non-Newtonian (mud/debris). The FLDWAV model includes the following features not found in DAMBRK: (a) the flood may occur in a system of interconnected rivers such as the main-stem river and its tributaries or through bifurcated channels and bypasses; (b) levee-overtopping/crevasse flows into and through levee-protected floodplains that may be compartmentalized by dikes and elevated roadways; (c) automatic calibration of Manning roughness coefficient for istorical floods; (d) improved numerical stability features; (e) menu-driven interactive data input; and (0 color-graphic displays of model output. FLDWAV is a generalized flood routing model that can be used by hydrologists/engineers for real-time flood forecasting of darn-break floods and/or natural floods, dam-breach flood analysis for sunny-day piping or overtopping associated with the PMF flood, floodplain inundation mapping for contingency darn-break flood planning, debris flow inundation mapping, and design of waterway improvements. 8 pp., 7 references.