Author(s): Louis M. Laushey; Baoguo Huang
Linked Author(s): Louis M. Laushey
Keywords: Real-time flood forecasting; Depths and crests; Wave velocities; Depth contour tracing; Moving reference frames
Abstract: Real-time reliable announcements of downstream flood stages can be made during rising depths being measured upstream. All that is needed are simple gages recording instantaneous depths that are being transmitted to an engineer making rapid calculations; then broadcasting the future depths at downstream times and locations. This provides an ultimate warning system, with credibility, to follow early warnings of only probable rainfall and stream flows. The flood wave velocity is the only variable needed, measurable with a string of depth gages spaced at known intervals. Rainfall intensity, rating curves, channel dimensions and roughness are not necessary to develop a theory. The real-time measurements of distance between gages divided by time of arrival of a constant incremental depth to be traced is indeed the correct wave velocity. This timely measured wave velocity will be found within the spectrum bounded by the theoretical kinematic and dynamic waves. The method involves a movable frame of reference (imagine walking along the bank) at the speed necessary to “see” a constant depth, like a surveyor tracing a ground contour of locations with equal elevations. Examples describe the method and results. The first is a computer simulation of a thunderstorm over a flashy tributary; the second uses observed depths measured in a large river. The method of real-time contour tracing calculated eventual depths that agreed with those measures later. The method can be used similarly for planning, estimation, and design of flood control systems.
Year: 2001