U.S.
GEOLOGICAL SURVEY
Open-File Report 02-256
Fifty-Year Flood-Inundation Maps for Nacaome, Honduras
By D.L. Kresch, M.C. Mastin, and T.D. Olsen
ABSTRACT
After the devastating floods caused by Hurricane Mitch in 1998, maps of the areas and depths of 50-year-flood inundation at 15 municipalities in Honduras were prepared as a tool for agencies involved in reconstruction and planning. This report, which is one in a series of 15, presents maps of areas in the municipality of Nacaome that would be inundated by 50-year floods on Río Nacaome, Río Grande, and Río Guacirope. Geographic Information System (GIS) coverages of the flood inundation are available on a computer in the municipality of Nacaome as part of the Municipal GIS project and on the Internet at the Flood Hazard Mapping Web page (http://mitchnts1.cr.usgs.gov/projects/floodhazard.html). These coverages allow users to view the flood inundation in much more detail than is possible using the maps in this report.
Water-surface elevations for 50-year-floods on Río Nacaome, Río Grande, and Río Guacirope at Nacaome were computed using HEC-RAS, a one-dimensional, steady-flow, step-backwater computer program. The channel and floodplain cross sections used in HEC-RAS were developed from an airborne light-detection-and-ranging (LIDAR) topographic survey of the area and ground surveys at two bridges.
The estimated 50-year-flood discharge for Río Nacaome at Nacaome, 5,040 cubic meters per second, was computed as the drainage-area-adjusted weighted average of two independently estimated 50-year-flood discharges for the gaging station Río Nacaome en Las Mercedes, located about 13 kilometers upstream from Nacaome. One of the discharges, 4,549 cubic meters per second, was estimated from a frequency analysis of the 16 years of peak-discharge record for the gage, and the other, 1,922 cubic meters per second, was estimated from a regression equation that relates the 50-year-flood discharge to drainage area and mean annual precipitation. The weighted-average of the two discharges is 3,770 cubic meters per second.
The 50-year-flood discharges for Río Grande, 3,890 cubic meters per second, and Río Guacirope, 1,080 cubic meters per second, were also computed by adjusting the weighted-average 50-year-flood discharge for the Río Nacaome en Las Mercedes gaging station for the difference in drainage areas between the gage and these river reaches.
Abstract
Introduction
Description of Study Area
Fifty-Year Flood Discharge
Water-Surface Profiles of the 50-Year Flood
Fifty-Year Flood-Inundation Maps
Data Availability
References Cited
This report and associated figures are available online in Portable Document Format (PDF). If you do not have the Adobe Acrobat PDF Reader, it is available for free download from Adobe Systems Incorporated.
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Geographic
Information System coverages of flood inundation and flood depth are available
at
http://mitchnts1.cr.usgs.gov/projects/floodhazard.html
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Send questions or comments about this report to the author, David L. Kresch (dlkresch@usgs.gov) 253.428.3600 ext. 2683.
For more information about USGS activities in Washington, visit the USGS Washington District home page.
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