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U.S. GEOLOGICAL SURVEY
Open-File Report 02-251

Fifty-Year Flood-Inundation Maps for Comayagua, Honduras

Prepared in cooperation with the
U.S. AGENCY FOR INTERNATIONAL DEVELOPMENT

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 the 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 Comayagua that would be inundated by 50-year floods on Río Humuya and Río Majada. Geographic Information System (GIS) coverages of the flood inundation are available on a computer in the municipality of Comayagua 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 Humuya and Río Majada at Comayagua were estimated 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.

The 50-year-flood discharge for Río Humuya at Comayagua, 1,400 cubic meters per second, was estimated using a regression equation that relates the 50-year-flood discharge to drainage area and mean annual precipitation. The reasonableness of the regression discharge was evaluated by comparing it with drainage-area-adjusted 50-year-flood discharges estimated for three long-term Río Humuya stream-gaging stations. The drainage-area-adjusted 50-year-flood discharges estimated from the gage records ranged from 946 to 1,365 cubic meters per second. Because the regression equation discharge agrees closely with the high end of the range of discharges estimated from the gaging-station records, it was used for the hydraulic modeling to ensure that the resulting 50-year-flood water-surface elevations would not be underestimated.

The 50-year-flood discharge for Río Majada at Comayagua (230 cubic meters per second) was estimated using the regression equation because there are no long-term gaging-stations on this river from which to estimate the discharge.

CONTENTS

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.

Download the report (PDF, 674 KB)

Select 11x17 high resolution versions of Figure 1 (PDF, 6.3 MB)
and Figure 4 (PDF, 767 KB) to view or print.

Geographic Information System coverages of flood inundation and flood depth are available at
http://mitchnts1.cr.usgs.gov/projects/floodhazard.html

Document Accessibility: Adobe Systems Incorporated has information about PDFs and the visually impaired. This information provides tools to help make PDF files accessible. These tools convert Adobe PDF documents into HTML or ASCII text, which then can be read by a number of common screen-reading programs that synthesize text as audible speech. In addition, an accessible version of Acrobat Reader 5.0 for Windows (English only), which contains support for screen readers, is available. These tools and the accessible reader may be obtained free from Adobe at Adobe Access.

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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