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USGS2015

Groundwater availability of the Columbia Plateau Regional Aquifer System, Washington, Oregon, and Idaho

The Columbia Plateau Regional Aquifer System (CPRAS) covers about 44,000 square miles of southeastern Washington, northeastern Oregon, and western Idaho. The area supports a $6-billion per year agricultural industry, leading the Nation in production of apples, hops, and eight other commodities. Groundwater pumpage and surface-water diversions supply water to croplands that account for about 5 percent of the Nation’s irrigated lands. Groundwater also is the primary source of drinking water for the more than 1.3 million people in the study area. Increasing competitive demands for water for municipal, fisheries/ecosystems, agricultural, domestic, hydropower, and recreational uses must be met by additional groundwater withdrawals and (or) by changes in the way water resources are allocated and used throughout the hydrologic system. As of 2014, most surface-water resources in the study area were either over allocated or fully appropriated, especially during the dry summer season. In response to continued competition for water, numerous water-management activities and concerns have gained prominence: water conservation, conjunctive use, artificial recharge, hydrologic implications of land-use change, pumpage effects on streamflow, and effects of climate variability and change. An integrated understanding of the hydrologic system is important in order to implement effective water-resource management strategies that address these concerns. To provide information to stakeholders involved in water-management activities, the U.S. Geological Survey (USGS) Groundwater Resources Program assessed the groundwater availability as part of a national study of regional systems (U.S. Geological Survey, 2008). The CPRAS assessment includes: The present status of groundwater resources, How these resources have changed over time, and Development and application of tools to estimate system responses to stresses from future uses and climate variability and change. This effort builds on previous investigations, especially the USGS Columbia Plateau Regional Aquifer-System Analysis study (CP-RASA). A major product of this new assessment is a numerical groundwater-flow model of the system. The model was used to estimate water-budget components of the hydrogeologic units composing the groundwater system, and to evaluate groundwater availability under existing land- and water-use conditions and a possible future climate scenario representing an increase in pumpage demand due to a warming climate. Information from this study also allowed for analysis of: The CPRAS for predevelopment times (pre-1920), Variations from 1920 through 2007, Conditions during 1985–2007 (referred to as “existing conditions”), and Changes in the system from predevelopment times. The model also is a useful tool for investigating water supply, water demand, management strategies, groundwater-surface water exchanges, and potential effects of changing climate on the hydrologic system.

Idaho, Oregon, Washington↗

USGS2012

Sources and sinks of nitrogen and phosphorus to a deep, oligotrophic lake, Lake Crescent, Olympic National Park, Washington

Lake Crescent, in Olympic National Park in the northwest corner of Washington State is a deep-water lake renowned for its pristine water quality and oligotrophic nature. To examine the major sources and sinks of nutrients (as total nitrogen, total phosphorus, and dissolved nitrate), a study was conducted in the Lake Crescent watershed. The study involved measuring five major inflow streams, the Lyre River as the major outflow, recording weather and climatic data, coring lake bed sediment, and analyzing nutrient chemistry in several relevant media over 14 months. Water samples for total nitrogen, total phosphorous, and dissolved nitrate from the five inflow streams, the outlet Lyre River, and two stations in the lake were collected monthly from May 2006 through May 2007. Periodic samples of shallow water from temporary sampling wells were collected at numerous locations around the lake. Concentrations of nutrients detected in Lake Crescent and tributaries were then applied to the water budget estimates to arrive at monthly and annual loads from various environmental components within the watershed. Other sources, such as leaf litter, pollen, or automobile exhaust were estimated from annual values obtained from various literature sources. This information then was used to construct a nutrient budget for total nitrogen and total phosphorus. The nitrogen budget generally highlights vehicle traffic-diesel trucks in particular-along U.S. Highway 101 as a potential major anthropogenic source of nitrogen compounds in the lake. In contrast, contribution of nitrogen compounds from onsite septic systems appears to be relatively minor related to the other sources identified.

Washington↗

USGS2009

Hydrogeologic Framework of the Yakima River Basin Aquifer System, Washington

The Yakima River basin aquifer system underlies about 6,200 square miles in south-central Washington. The aquifer system consists of basin-fill deposits occurring in six structural-sedimentary basins, the Columbia River Basalt Group (CRBG), and generally older bedrock. The basin-fill deposits were divided into 19 hydrogeologic units, the CRBG was divided into three units separated by two interbed units, and the bedrock was divided into four units (the Paleozoic, the Mesozoic, the Tertiary, and the Quaternary bedrock units). The thickness of the basin-fill units and the depth to the top of each unit and interbed of the CRBG were mapped. Only the surficial extent of the bedrock units was mapped due to insufficient data. Average mapped thickness of the different units ranged from 10 to 600 feet. Lateral hydraulic conductivity (Kh) of the units varies widely indicating the heterogeneity of the aquifer system. Average or effective Kh values of the water-producing zones of the basin-fill units are on the order of 1 to 800 ft/d and are about 1 to 10 ft/d for the CRBG units as a whole. Effective or average Kh values for the different rock types of the Paleozoic, Mesozoic, and Tertiary units appear to be about 0.0001 to 3 ft/d. The more permeable Quaternary bedrock unit may have Kh values that range from 1 to 7,000 ft/d. Vertical hydraulic conductivity (Kv) of the units is largely unknown. Kv values have been estimated to range from about 0.009 to 2 ft/d for the basin-fill units and Kv values for the clay-to-shale parts of the units may be as small as 10-10 to 10-7 ft/d. Reported Kv values for the CRBG units ranged from 4x10-7 to 4 ft/d. Variations in the concentrations of geochemical solutes and the concentrations and ratios of the isotopes of hydrogen, oxygen, and carbon in groundwater provided information on the hydrogeologic framework and groundwater movement. Stable isotope ratios of water (deuterium and oxygen-18) indicated dispersed sources of groundwater recharge to the CRBG and basin-fill units and that the source of surface and groundwater is derived from atmospheric precipitation. The concentrations of dissolved methane were larger than could be attributable to atmospheric sources in more than 80 percent of wells with measured methane concentrations. The concentrations of the stable isotope of carbon-13 of methane were indicative of a thermogenic source of methane. Most of the occurrences of methane were at locations several miles distant from mapped structural fault features, suggesting the upward vertical movement of thermogenic methane from the underlying bedrock may be more widespread than previously assumed or there may be a more general occurrence of unmapped (buried) fault structures. Carbon and tritium isotope data and the concentrations of dissolved constituents indicate a complex groundwater flow system with multiple contributing zones to groundwater wells and relative groundwater residence time on the order of a few tens to many thousands of years. Potential mean annual recharge for water years 1950-2003 was estimated to be about 15.6 in. or 7,149 ft3/s (5.2 million acre-ft) and includes affects of human activities such as irrigation of croplands. If there had been no human activities (predevelopment conditions) during that time period, estimated recharge would have been about 11.9 in. or 5,450 ft3/s (3.9 million acre-ft). Estimated mean annual recharge ranges from virtually zero in the dry parts of the lower basin to more than 100 in. in the humid uplands, where annual precipitation is more than 120 in. Groundwater in the different hydrogeologic units occurs under perched, unconfined, semiconfined, and confined conditions. Groundwater moves from topographic highs in the uplands to topographic low areas along the streams. The flow system in the basin-fill units is compartmentalized due to topography and geologic structure. The flow system also is compartmentalized for the CRBG units but not to as large

Scientific Investigations Report↗

USGS2007

Estimates of Monthly Ground-Water Recharge to the Yakima River Basin Aquifer System, Washington, 1960-2001, for Current Land-Use and Land-Cover Conditions

Unique ID grid with a unique value per Hydrologic Response Unit (HRU) per basin in reference to the estimated ground-water recharge for current conditions in the Yakima Basin Aquifer System, (USGS report SIR 2007-5007). Total 78,144 unique values. This grid made it easy to provide estimates of monthly ground-water recharge for water years 1960-2001in an electronic format for water managers, planners, and hydrologists, that could be related back to a spatially referenced grid by the unique ID.

Open-File Report↗

USGS2007

Estimates of ground-water recharge to the Yakima River Basin aquifer system, Washington, for predevelopment and current land-use and land-cover conditions

Two models were used to estimate ground-water recharge to the Yakima River Basin aquifer system, Washington for predevelopment (estimate of natural conditions) and current (a multi-year, 1995-2004, composite) land-use and land-cover conditions. The models were the Precipitation-Runoff Modeling System (PRMS) and the Deep Percolation Model (DPM) that are contained in the U.S. Geological Survey's Modular Modeling System. Daily values of recharge were estimated for water years 1950-98 using previously developed PRMS-watershed models for four mainly forested upland areas, and for water years 1950-2003 using DPM applied to 17 semiarid to arid areas in the basin. The mean annual recharge under predevelopment conditions was estimated to be about 11.9 in. or 5,450 ft 3 /s (about 3.9 million acre-ft) for the 6,207 mi 2 in the modeled area. In the modeled areas, recharge ranged from 0.08 in. (1.2 ft 3 /s) to 34 in. (2,825 ft 3 /s). About 97 percent of the recharge occurred in the 3,667 mi 2 area included in the upland-area models, but much of this quantity is not available to recharge the bedrock hydrogeologic units. Only about 1.0 in., or 187 ft 3 /s (about 0.14 million acre-ft), was estimated to occur in the 2,540 mi 2 area included in the semiarid to arid lowland modeled areas. The mean annual recharge to the aquifer system under current conditions was estimated to be about 15.6 in., or 7,149 ft 3 /s (about 5.2 million acre-ft). The increase in recharge is due to the application of irrigation water to croplands. The annual quantity of irrigation was more than five times the annual precipitation for some of the modeled areas. Mean annual actual evapotranspiration was estimated to have increased from predevelopment conditions by more than 1,700 ft 3 /s (about 1.2 million acre-ft) due to irrigation.

Washington↗

USGS2002

Fifty-year flood-inundation maps for Catacamas, Honduras

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 Catacamas that would be inundated by a 50-year-flood of Rio Catacamas. Geographic Information System (GIS) coverages of the flood inundation are available on a computer in the municipality of Catacamas 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 a 50-year-flood on Rio Catacamas at Catacamas 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 Rio Catacamas at Catacamas, 216 cubic meters per second, was estimated using a regression equation that relates the 50-year-flood discharge to drainage area and mean annual precipitation because there are no long-term stream-gaging stations on the river from which to estimate the discharge. The drainage area and mean annual precipitation estimated for Rio Catacamas at Catacamas are 45.4 square kilometers and 1,773 millimeters, respectively.

Catacamas↗

USGS2002

Fifty-year flood-inundation maps for Choloma, Honduras

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 Choloma that would be inundated by a 50-year flood of Rio Choloma. Geographic Information System (GIS) coverages of the flood inundation are available on a computer in the municipality of Choloma as part of the in 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 a 50-year-flood on Rio Choloma at Choloma were determined 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. There are no nearby long-term stream-gaging stations on Rio Choloma; therefore, the 50-year-flood discharge for Rio Choloma, 370 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 drainage area and mean annual precipitation estimated for Rio Choloma at Choloma are 89.5 square kilometers and 2,164 millimeters, respectively.

Choloma↗

USGS2002

Fifty-year flood-inundation maps for Choluteca, Honduras

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 Choluteca that would be inundated by 50-year floods on Rio Choluteca and Rio Iztoca. Geographic Information System (GIS) coverages of the flood inundation are available on a computer in the municipality of Choluteca 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 Rio Choluteca and Rio Iztoca at Choluteca 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 estimated 50-year-flood discharge for Rio Choluteca at Choluteca is 4,620 cubic meters per second, which is the drainage-area-adjusted weighted-average of two independently estimated 50-year-flood discharges for the gaging station Rio Choluteca en Puente Choluteca. One discharge, 4,913 cubic meters per second, was estimated from a frequency analysis of the 17 years of peak discharge record for the gage, and the other, 2,650 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 at the gage is 4,530 cubic meters per second. The 50-year-flood discharge for the study area reach of Rio Choluteca was estimated by multiplying the weighted discharge at the gage by the ratio of the drainage areas upstream from the two locations. The 50-year-flood discharge for Rio Iztoca, which was estimated from the regression equation, is 430 cubic meters per second.

Choluteca↗

USGS2002

Fifty-year flood-inundation maps for Comayagua, Hondura

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 Rio Humuya and Rio 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 Rio Humuya and Rio 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 Rio 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 Rio 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 Rio 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.

Comayagua↗

USGS2002

Fifty-year flood-inundation maps for El Progreso, Honduras

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 El Progreso that would be inundated by a 50-year flood of Rio Pelo. Geographic Information System (GIS) coverages of the flood inundation are available on a computer in the municipality of El Progreso 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 a 50-year-flood on Rio Pelo at El Progreso 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. There are no nearby long-term stream-gaging stations on Rio Pelo; therefore, the 50-year-flood discharge for Rio Pelo, 235 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 drainage area and mean annual precipitation estimated for Rio Pelo at El Progreso are 47.4 square kilometers and 1,920 millimeters, respectively.

El Progreso↗

USGS2002

Fifty-year flood-inundation maps for La Ceiba, Honduras

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 La Ceiba that would be inundated by a 50-year-flood of Rio Cangrejal. Geographic Information System (GIS) coverages of the flood inundation are available on a computer in the municipality of La Ceiba 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 a 50-year-flood discharge of 1,030 cubic meters per second on Rio Cangrejal at La Ceiba 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. There are no nearby long-term stream-gaging stations on Rio Cangrejal; therefore, the 50-year-flood discharge for Rio Cangrejal at La Ceiba was estimated using a regression equation that relates the 50-year-flood discharge to drainage area and mean annual precipitation. The drainage area and mean annual precipitation estimated for Rio Cangrejal at La Ceiba are 498 square kilometers and 2,306 millimeters, respectively.

La Ceiba↗

USGS2002

Fifty-year flood-inundation maps for La Lima, Honduras

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 La Lima that would be inundated by Rio Chamelecon with a discharge of 500 cubic meters per second, the approximate capacity of the river channel through the city of La Lima. The 50-year flood (2,400 cubic meters per second), the original design flow to be mapped, would inundate the entire area surveyed for this municipality. Because water-surface elevations of the 50-year flood could not be mapped properly without substantially expanding the area of the survey, the available data were used instead to estimate the channel capacity of Rio Chamelecon in La Lima by trial-and-error runs of different flows in a numerical model and to estimate the increase in height of levees needed to contain flows of 1,000 and 2,400 cubic meters per second. Geographic Information System (GIS) coverages of the flood inundation are available on a computer in the municipality of La Lima 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 various discharges on Rio Chamelecon at La Lima were determined 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 three bridges. Top-of-levee or top-of-channel-bank elevations and locations at the cross sections were critical to estimating the channel capacity of Rio Chamelecon. These elevations and locations are provided along with the water-surface elevations for the 500-cubic-meter-per-second flow of Rio Chamelecon. Also, water-surface elevations of the 1,000 and 2,400 cubic-meter-per-second flows are provided, assuming that the existing levees are raised to contained the flows.

La Lima↗

USGS2002

Fifty-year flood-inundation maps for Nacaome, Honduras

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 Rio Nacaome, Rio Grande, and Rio 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 Rio Nacaome, Rio Grande, and Rio 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 Rio 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 Rio 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 Rio Grande, 3,890 cubic meters per second, and Rio Guacirope, 1,080 cubic meters per second, were also computed by adjusting the weighted-average 50-year-flood discharge for the Rio Nacaome en Las Mercedes gaging station for the difference in drainage areas between the gage and these river reaches.

Nacaome↗

USGS2002

Fifty-year flood-inundation maps for Olanchito, Honduras

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 Olanchito that would be inundated by a 50-year-flood of Rio Uchapa. Geographic Information System (GIS) coverages of the flood inundation are available on a computer in the municipality of Olanchito 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 a 50-year-flood discharge of 243 cubic meters per second on Rio Uchapa at Olanchito 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. There are no nearby long-term stream-gaging stations on Rio Uchapa; therefore, the 50-year-flood discharge for Rio Uchapa was estimated using a regression equation that relates the 50-year-flood discharge to drainage area and mean annual precipitation. The drainage area and mean annual precipitation estimated for Rio Uchapa at Olanchito are 97.1 square kilometers and 1,178 millimeters, respectively.

Olanchito↗

USGS2002

Fifty-Year Flood-Inundation Maps for Santa Rosa de Aguan, Honduras

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 coastal municipality of Santa Rosa de Aguan that are prone to oceanic storm-surge flooding and wave action. The 50-year flood on the Rio Aguan (4,270 cubic meters per second), would inundate most of the area surveyed for this municipality and beyond. Therefore a detailed numerical hydraulic model was not developed for this municipality as it was for the others. The 50-year storm surge would likely produce higher water levels than the 50-year flood on the river during normal astronomical tides. The elevation of the 50-year storm surge was estimated to be 4.35 meters above normal sea level, based on hurricane probabilities and published storm-surge elevations associated with various hurricane categories. Flood-inundation maps, including areas of wave-action hazard and a color-shaded elevation map, were created from the available data and the estimated 50-year storm tide. Geographic Information System (GIS) coverages of the hazard areas are available on a computer in the municipality of Santa Rosa de Aguan as part of the Municipal GIS project and on the Internet at the Flood Hazard Mapping Data Web page (http://mitchnts1.cr.usgs.gov/projects/floodhazard.html). These coverages allow users to view the maps in much more detail than is possible using the maps in this report.

Santa Rosa de Aguan↗

USGS2002

Fifty-year flood-inundation maps for Siguatepeque, Honduras

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 Siguatepeque that would be inundated by 50-year floods on Rio Selguapa, Rio Guique, Rio Celan, Rio Calan, and Quebrada Chalantuma. Geographic Information System (GIS) coverages of the flood inundation are available on a computer in the municipality of Siguatepeque 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 each of the streams studied 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 six bridges. There are no nearby long-term stream-gaging stations on any of the streams studied; therefore, the 50-year-flood discharges were estimated using a regression equation that relates the 50-year-flood discharge to drainage area and mean annual precipitation. The 50-year-flood discharges estimated for Rio Selguapa, Rio Guique, Rio Celan, Rio Calan, and Quebrada Chalantuma are 323, 168, 161, 146, and 90 cubic meters per second, respectively.

Siguatepeque↗

USGS2002

Fifty-year flood-inundation maps for Sonaguera, Honduras

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 Sonaguera that would be inundated by a 50-year flood of Rio Sonaguera and its tributary, Rio Juan Lazaro. Geographic Information System (GIS) coverages of the flood inundation are available on a computer in the municipality of Sonaguera 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 an estimated 50-year-flood on Rio Sonaguera and Rio Juan Lazaro at Sonaguera were determined 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 a ground survey at the bridge. There are no nearby long-term stream-gaging stations on Rio Sonaguera or Rio Juan Lazaro; therefore, the 50-year-flood discharge for Rio Sonaguera above the confluence with Rio Juan Lazaro, 194 cubic meters per second; for Rio Juan Lazaro at its mouth, 168 cubic meters per second, and for Rio Sonaguera at the downstream end of the study area, 282 cubic meters per second; were estimated using a regression equation that relates the 50-year-flood discharge to drainage area and mean annual precipitation.

Sonaguera↗

USGS2002

Fifty-year flood-inundation maps for Tocoa, Honduras

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 Tocoa that would be inundated by a 50-year flood of Rio Tocoa. Geographic Information System (GIS) coverages of the flood inundation are available on a computer in the municipality of Tocoa 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 an estimated 50-year-flood on Rio Tocoa at Tocoa 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 and a ground survey at one bridge. There are no nearby long-term stream-gaging stations on Rio Tocoa; therefore, the 50-year-flood discharge for Rio Tocoa, 552 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 drainage area and mean annual precipitation estimated for Rio Tocoa at Tocoa are 204 square kilometers and 1,987 millimeters, respectively. It was assumed that a portion of the 50-year flood, 200 cubic meters per second, would escape the main channel and flow down a side channel before re-entering the main channel again near the lower end of the study area.

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