Flood-Inundation Maps for La Lima, Honduras
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Prepared in cooperation with the U.S Agency for International Development 1 Flood-Inundation Maps 2 for La Lima, Honduras 3 U.S. Geological Survey Open-File Report 02-255 4 5 6 7 88 9 La Lima 10 11 12 13 14 U.S. Department of the Interior U.S. Geological Survey 15 Fifty-Year Flood-Inundation Maps for La Lima, Honduras By Mark C. Mastin and Theresa D. Olsen U.S. GEOLOGICAL SURVEY Water-Resources Investigations Report 02-255 Prepared in cooperation with the U.S. AGENCY FOR INTERNATIONAL DEVELOPMENT Tacoma, Washington 2002 U.S. DEPARTMENT OF THE INTERIOR GALE A. NORTON, Secretary U.S. GEOLOGICAL SURVEY Charles G. Groat, Director Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government. For additional information write to: Copies of this report can be purchased from: District Chief U.S. Geological Survey U.S. Geological Survey Information Services 1201 Pacific Avenue – Suite 600 Building 810 Tacoma, Washington 98402 Box 25286, Federal Center http://wa.water.usgs.gov Denver, CO 80225-0286 CONTENTS Abstract ................................................................................................................................................................ 1 Introduction .......................................................................................................................................................... 2 Purpose, Scope, and Methods ..................................................................................................................... 3 Acknowledgments....................................................................................................................................... 3 Description of Study Area.................................................................................................................................... 3 Water-Surface Profiles ......................................................................................................................................... 5 Flood-Inundation Maps........................................................................................................................................ 10 Data Availability .................................................................................................................................................. 10 References Cited .................................................................................................................................................. 11 Contents iii FIGURES Figure 1. Map showing location of study area and cross sections, and the area of inundation for a dicharge of 500 cubic meters per second on Río Chamelecón at La Lima, Honduras.............. 4 Figure 2. Map showing depth of inundation of a discharge of 500 cubic feet per second, extent of simulated flooding, and location of cross sections on Río Chamelecón at La Lima, Honduras ........................................................................................................................ 7 Figure 3. Graph showing water-surface profiles, estimated using the step-backwater model HEC-RAS, for discharges of 500, 1,000, and 2,400 cubic meters per second (m3/s) confined within the main channel and levee or bank elevations on Río Chamelecón at La Lima, Honduras ........................................................................................................................ 9 iv Figures TABLES Table 1. Estimated water-surface elevations for a discharge of 500 cubic meters per second; estimated water-surface elevations for discharges of 1,000 and 2,400 cubic meters per second assuming that existing levees and channel banks are raised to confine the flows; and bank or levee elevations along Río Chamelecón at La Lima, Honduras .................................... 6 Tables v CONVERSION FACTORS AND VERTICAL DATUM CONVERSION FACTORS Multiply By To obtain cubic meter per second (m3/s) 35.31 cubic foot per second kilometer (km) 0.6214 mile meter (m) 3.281 foot millimeter (mm) 0.03937 inch square kilometer (km2) 0.3861 square mile VERTICAL DATUM Elevation: In this report "elevation" refers to the height, in meters, above the ellipsoid defined by the World Geodetic System of 1984 (WGS 84). vi Conversion Factors and Vertical Datum Fifty-Year Flood-Inundation Maps for La Lima, Honduras By Mark C. Mastin and Theresa D. Olsen ABSTRACT inundation are available on a computer in the municipality of La Lima as part of the Municipal After the devastating floods caused by GIS project and on the Internet at the Flood Hurricane Mitch in 1998, maps of the areas and Hazard Mapping Web page depths of the 50-year-flood inundation at 15 (http://mitchnts1.cr.usgs.gov/projects/floodhazard. municipalities in Honduras were prepared as a tool html). These coverages allow users to view the for agencies involved in reconstruction and flood inundation in much more detail than is planning. This report, which is one in a series of possible using the maps in this report. 15, presents maps of areas in the municipality of Water-surface elevations for various La Lima that would be inundated by Río discharges on Río Chamelecón at La Lima were Chamelecón with a discharge of 500 cubic meters determined using HEC-RAS, a one-dimensional, per second, the approximate capacity of the river steady-flow, step-backwater computer program. channel through the city of La Lima. The 50-year The channel and floodplain cross sections used in flood (2,400 cubic meters per second), the original HEC-RAS were developed from an airborne light- design flow to be mapped, would inundate the detection-and-ranging (LIDAR) topographic entire area surveyed for this municipality. Because survey of the area and ground surveys at three water-surface elevations of the 50-year flood bridges. Top-of-levee or top-of-channel-bank could not be mapped properly without elevations and locations at the cross sections were substantially expanding the area of the survey, the critical to estimating the channel capacity of Río available data were used instead to estimate the Chamelecón. These elevations and locations are channel capacity of Río Chamelecón in La Lima provided along with the water-surface elevations by trial-and-error runs of different flows in a for the 500-cubic-meter-per-second flow of Río numerical model and to estimate the increase in Chamelecón. Also, water-surface elevations of the height of levees needed to contain flows of 1,000 1,000 and 2,400 cubic-meter-per-second flows are and 2,400 cubic meters per second. Geographic provided, assuming that the existing levees are Information System (GIS) coverages of the flood raised to contained the flows. Abstract 1 INTRODUCTION every 50 years. The 50-year flood was estimated to be 2,400 m3/s from a regression equation that relates the In late October 1998, Hurricane Mitch struck the 50-year-flood discharge with drainage basin area and mainland of Honduras, triggering destructive mean annual precipitation (Mastin, 2002). The landslides, flooding, and other associated disasters that drainage area of Río Chamelecón at La Lima was overwhelmed the country’s resources and ability to determined to be 3,757 square kilometers (km2) using quickly rebuild itself. The hurricane produced more a geographic information system (GIS) program to than 450 millimeters (mm) of rain in 24 hours in parts analyze a digital elevation model (DEM) with a of Honduras and caused significant flooding along 93-meter cell resolution from the U.S. National most rivers in the country. A hurricane of this intensity Imagery and Mapping Agency (David Stewart, USGS, is a rare event, and Hurricane Mitch is listed as the written commun., 1999). The mean annual most deadly hurricane in the Western Hemisphere since precipitation over the Río Chamelecón drainage basin the “Great Hurricane” of 1780. However, other was determined to be 1,568 mm using a GIS program destructive hurricanes have hit Honduras in recent to analyze a digitized map of mean annual precipitation history. For example, Hurricane Fifi hit Honduras in at a scale of 1:2,500,000 (Morales-Canales, 1997-1998, September 1974, causing 8,000 deaths (Rappaport and p. 15). For comparison, the flood due to Hurricane Fernandez-Partagas, 1997). Mitch was estimated by a three-section, slope-area As part of a relief effort in Central America, the indirect method to be 4,700 m3/s upstream at Río U.S. Agency for International Development (USAID), Chamelecón near El Tablón, which drains 2,670 square with help from the U.S. Geological Survey (USGS), kilometers (Mark Smith, U.S. Geological Survey, developed a program to aid Central America in written commun., 2001). The Hurricane Mitch flood on rebuilding itself. A top priority identified by USAID the Río Chamelecón combined with floodwaters of the was the need for reliable flood-hazard maps in Río Ulua to completely inundate the town of La Lima Honduras to help plan the rebuilding of housing and and much of the Sula Valley. infrastructure. The Water Resources Division of the It soon became apparent that the 50-year-flood USGS in Washington State, in coordination with the discharge would overwhelm the capacity of the channel International Water Resources Branch of the USGS, and inundate the entire area that was surveyed for La was given the task to develop flood-hazard maps for Lima. The full extent of the flooding could not be 15 municipalities in Honduras: Catacamas, Choloma, determined from the limited survey that was made; Choluteca, Comayagua,