Flood mapping

We have established a protocol for estimating the impacts of specific dam breach scenarios in Hawaii. There are three major steps conducting one-dimensional hydraulic analyses, producing two-dimensional flood maps, and estimating the impacts on the community. 

This work was funded by the U.S. National Aeronautical and Space Administration (Contract NASW-99044). The DEM and GIS infrastructure data were supplied by the Pacific Disaster Center. The method for preparing the two-dimensional flood maps is based in part by a method described to us by Andy Rost of the National Operational Hydrologic Remote Sensing Center. 

A general flow map of different hydrodynamic conditions (Fig. 23) consists of regions of flooding, dispersion, and recirculation on a plot of N vs for a Rushton turbine. For a low viscosity aqueous/air system, the gas flow numbers for the three conditions are given hy FI = 30Fr[D/TY for flooding, = 0.2Fr° (F/r)° for complete dispersion, and =13FF D/TY for recirculation. 

Revise codes, such as flood plain mapping and climate data and return frequencies for hazard-prone areas, adjusting to new realities, i.e., 100-year floods become 500-year floods, higher snow and wind loads. 

Particular conditions may occur for two-phase downflows in vertical or inclined channels (ducts) that are not completely described by the flow regime maps. Flooding occurs as the rising vapor completely blocks descending liquid. With lowering velocities of the vapor phase, this condition is preceded by the phenome-... 

A first-order estimate of the impacts of the flood scenario can be obtained through an evaluation of the flood depth map after it has been overlaid onto an electronic version of a standard topographic map that depicts roads, buildings, and public facilities. Such maps are useful for preparing evacuation plans and selecting locations for roadblocks. The FLDWAV output files may be consulted to determine the time characteristics of the flood, such as the time from the dam breach to the onset of flooding, and the duration of flooding. 

The methods described above were tested at two sites in Hawaii The Nuuanu reservoir on Oahu, which is above downtown Honolulu, and the Waikoloa Dam on Hawaii Island, which is above the town of Waimea. In both cases the analyses were performed with and without topographic data obtained by a field survey crew. Detailed results from the ca e studies and results of a sensitivity analysis are reported elsewhere. The flood inundation maps produced for Waimea and Honolulu were overlaid onto several GIS infrastructure layers. These layers included major roads, secondary roads, schools, nursing homes, hospitals, police stations, fire stations, civil defense headquarters, chemical plants, electric plants and transmission lines, water plants, and wells (which could be contaminated by floodwaters). Critical facilities in the flood zone were identified and listed along with their mailing addresses and phone numbers of contact personnel. 

From 1943 through 1971 the precipitation at the Lake Arrowhead Fire District station about 1 mile ENE of the study area averaged 40.04 inches (January-December). The standard deviation of 18.05 was exceeded five times below and five times above the mean. The 1870—1970 average estimated from isohyetals (San Bernardino County Flood Control Agency map) is between 35 and 40 inches. A dry trend continued without interruption from 1959 through 1964 with precipitation averaging 11.21 inches below the 1943-1971 average. Since 1964 the annual precipitation was 1965, 67.19 1966, 38.01 1967, 55.87 1968, 20.06 1969, 98.54 1970, 34.61 and 1971, 33.80. 

Area subject to flooding estimated from geomorphological maps derived from the SLAR imagery occupies about 78,000 km along the Amazon mainstem and an additional 62,000 km along the lower reaches of the four major tributaries (Sippel et al. 1992 52.5 W to 70.5-W, reaches 1 through 12). Islands comprise a small proportion of the total main-stem floodplain, except in the Amazon delta which is excluded from our... 

Two major types of hydrologic and morphometric information are lacking for almost all Amazon floodplain lakes stage data and bathymetric maps. Therefore, it is not possible to determine directly the seasonal and interannual changes in open water area, total flooded area, or volume of water resid-... 

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