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At least 343 records · Page 19Linked to original sources
USGS1987

Multiple-regression equations for estimating low flows at ungaged stream sites in Ohio

This report presents multiple-regression equations for estimating selected low-flow characteristics for most unregulated Ohio streams at sites where little or no discharge data are available. The equations relate combinations of drainage area, main-channel length, main-channel slope, average basin elevation, forested area, average annual precipitation, and an index of infiltration to low flows with durations of 7 and 30 days and average recurrence intervals of 2 and 10 years. Data from 132 long-term continuous-record gaging stations and partial-record sites in Ohio were used in the analyses. Multiple-regression analyses were first performed by using data from all 132 sites in an attempt to develop equations that would be applicable statewide. Standard errors for the statewide equations were too high (111 to 189 percent) for them to be of practical use in estimating low streamflows. Data for the state were then subdivided into five regions, and multiple-regression equations were developed for each region. Standard errors for four of the five regions improved, and raged from 43 to 106 percent. Standard errors for region 5 remained high (74 to 129 percent). The multiple-regression equations presented in this report are not applicable to streams with significant low-flow regulation. The equations also are not applicable if (1) the site has been gaged and low-flow estimates have been developed from gaging-station records, (2) low flow can be estimated by the drainage-area transference method from data for a nearby gaged site, or (3) a sufficient number of partial-record measurements made at the site can be adquately correlated with concurrent base flows at a suitable index station.

Water-Resources Investigations Report↗
USGS1996

Mass balance, meteorological, ice motion, surface altitude, and runoff data at Gulkana Glacier, Alaska, 1992 balance year

The 1992 measured winter snow, maximum winter snow, net, and annual balances in the Gulkana Glacier basin were evaluated on the basis of meteorological, hydrological, and glaciological data measured in the basin and are reported herein. Averaged over the glacier, the measured winter snow balance was 0.97 meters on March 26, 1992; the maximum winter snow balance was 1.05 meters on May 19, 1992; the net balance (from September 8, 1991 to August 17, 1992) was -0.29 meters; and the annual balance (October 1, 1991 to September 30, 1992) was -0.38 meters. Ice surface, motion, and altitude changes measured at three index sites document seasonal changes in ice speed and glacier thickness. Annual stream runoff was 1.24 meters averaged over the basin.

Water-Resources Investigations Report↗
USGS1997

Generalized skew coefficients for flood-frequency analysis in Minnesota

This report presents an evaluation of generalized skew coefficients used in flood-frequency analysis. Station skew coefficients were computed for 267 long-term stream-gaging stations in Minnesota and the surrounding states of Iowa, North and South Dakota, Wisconsin, and the provinces of Manitoba and Ontario, Canada. Generalized skew coefficients were computed from station skew coefficients using a locally weighted regression technique. The resulting regression trend surface was the generalized skew coefficient map, except for the North Shore area, and has a mean square error of 0.182.

Water-Resources Investigations Report↗
USGS2000

Preliminary assessment of phosphorus transport in the Cheney Reservoir watershed, south-central Kansas, 1997-98

A 5-year assessment of water-quality conditions is being conducted in the 933-square-mile Cheney Reservoir watershed of south-central Kansas. Part of this assessment is to define source areas of phosphorus in the watershed and to quantify its transport into Cheney Reservoir. Concern exists for the quality of water in Cheney Reservoir particularly in regards to phosphorus because of its possible relation to algal blooms and subsequent taste and odor problems in treated drinking water from the reservoir. The purpose of this report is to present the results of a preliminary assessment of phosphorus transport during the first 2 complete years (1997-98) of data collection. Annual phosphorus loads and yields were estimated, using regression analysis, at six sampling sites in the Cheney Reservoir watershed. Phosphorus loads and yields for the entire watershed also were estimated. Estimated phosphorus loads at all sampling sites and two additional subwatershed areas were substantially larger in 1998 than in 1997, with a median increase of 68 percent. This increase was mostly the result of wetter conditions in 1998. Estimated mean annual phosphorus yields for 1997-98 (upstream from Cheney Reservoir) ranged from 0.131 to 0.371 pound per acre. Much of the between-site variability in yields was attributed to variability in water yield and does not represent substantial changes in land-use or land-management practices. On average, about 62 percent of the phosphorus load to the reservoir was retained in the reservoir. A mean annual phosphorus yield for 1997-98 for the entire Cheney Reservoir watershed was estimated at 0.20 pound per acre. This compares to mean annual phosphorus yields of 1.76 and 0.05 pounds per acre reported in previous reservoir watershed assessments conducted in the Hillsdale Lake watershed in eastern Kansas in 1996 and the Webster Reservoir watershed in western Kansas in 1998, respectively. However, because of some uncertainty of the representativeness of the Cheney Reservoir watershed mean annual yield for 1997-98, it is suggested that a detailed examination of reservoir bottom sediment and associated phosphorus might provide estimates of historical mean annual phosphorus loads to Cheney Reservoir and of yields from the watershed with which to compare results of the 1997-98 study.

Water-Resources Investigations Report↗
USGS1993

Bathymetry of Lake Michie, Durham County, North Carolina, 1990-92

This map report presents the results of a bathymetric survey conducted as part of a 1990-92 study on the effects of sedimentation on Lake Michie, located in northeastern Durham County, North Carolina. Bathymetric data collected at the lake during 1990-92 indicate that, under normal pool conditions at the spillway elevation of 341.0 feet above sea level, the storage volume is 11,070 acre-feet, and the surface area is 508.7 acres. The maximum depth recorded in the lake was 75 feet at approximately 500 feet upstream of Lake Michie Dam.

North Carolina↗
USGS1996

Water-quality assessment of the Rio Grande Valley, Colorado, New Mexico, and Texas: Occurrence and distribution of selected pesticides and nutrients at selected surface-water sites in the Mesilla Valley, 1994-95

The Rio Grande Valley study unit of the U.S. Geological Survey National Water-Quality Assessment Program conducted a two-phase synoptic study of the occurrence and distribution of pesticides and nutrients in the surface water of the Mesilla Valley, New Mexico and Texas. Phase one, conducted in April-May 1994 during the high-flow irrigation season, consisted of a 6-week time- series sampling event during which 17 water-column samples were collected at 3 main-stem sites on the Rio Grande and a synoptic irrigation-run sampling event during which 19 water-column samples were collected at 7 main-stem sites, 10 drain sites, and 2 sites at the discharges of wastewater-treatment plants. Three samples are included in both the time-series and irrigation-run events. Phase two, conducted in January 1995 during the low-flow non-irrigation season, consisted of a non-irrigation synoptic sampling event during which 18 water-column samples were collected at seven main-stem sites, nine drain sites, and two sites at the discharges of wastewater-treatment plants and a bed- material sampling event during which 6 bed-material samples were collected at six sites near the mouths of drains that discharge to the Rio Grande. The 51 water-column samples were analyzed for 78 pesticides and metabolites and 8 nutrients along with other constituents. The six bed-material samples were analyzed for 21 pesticides and metabolites, gross polychlorinated biphenyls, and gross polychlorinated naphthalenes. The presence of dissolved pesticides in the surface water of the Mesilla Valley is erratic. A total of 100 detections of 17 different pesticides were detected in 44 of the water-column samples. As many as 38 percent of these detections may be attributed to pesticide use upstream from the valley or to nonagricultural pesticide use within the valley. There were 29 detections of 10 different pesticides in 17 samples during the irrigation run and 41 detections of 13 pesticides in 16 samples during the non-irrigation run. Nine pesticides were detected during both phases of the study. The most commonly detected pesticides in the water-column samples were DCPA, which was detected in 29 samples, and metolachlor, which was detected in 17 of the samples. DCPA was detected throughout the Mesilla Valley, whereas metolachlor was detected mainly in the northern and central parts of the valley. The maximum pesticide concentration found during the study was 0.75 microgram per liter of carbofuran, which was detected at the East Side Drain site during the irrigation run. No water-column pesticide concentration exceeded U.S. Environmental Protection Agency's drinking-water standards or any applicable Federal or State criteria or guidelines. A total of 21 occurrences of six pesticides and metabolites were found in the bed-material samples. Chlordane, diazinon, and methyl parathion were detected once each, whereas DDD, DDE, and DDT were detected at all six bed-material sites. Water-column samples for the analysis of nutrient concentrations were collected at all sampling sites during both phases of the study. The concentrations of each nutrient ranged from at or below the individual minimum reporting level to as much as two or three orders of magnitude larger than the minimum reporting level. The concentration of each nutrient was left skewed with most of the values toward the lower end of the range. The larger concentrations of each nutrient, except dissolved nitrite plus nitrate, were associated with wastewater-treatment- plant sites 4 and 16. The larger concentrations of dissolved nitrite plus nitrate were generally associated with the non- irrigation run; however, the largest concentration was at site 4 during the irrigation run. During this study, the Mesilla Valley as a unit was a source of nutrients to the Rio Grande. Wi

New Mexico↗
USGS1983

Identification and classification of perennial streams of Arkansas

Perennial streams are identified in a map and classified according to the relative magnitude of their 7-day, 10-year low flows. Perennial streams are identified for the entire State of Arkansas with the exception of the Mississippi Alluvial Plain. Also presented are the 7-day, 10-year low flow values at continuous-record and low-flow partial-record stations statewide. Perennial streams are defined in this report as having 7-day, 10-year low flows greater than zero. The perennial stream drainage was delineated using data from continuous-record and low-flow partial-record stations, and reconnaissance-site observations. The reconnaissance was conducted during the unusually dry summer of 1980. In analysis, the State was divided into hydrologic regions; they were used in conjunction with index stations to establish the recurrence intervals of flow observed, during the reconnaissance. When necessary, relations were developed by region to adjust observed flow to 10-year recurrence interval flows. (USGS)

Arkansas↗
USGS1988

Streamflows in Wyoming

A description of the occurrence and availability of surface waters in Wyoming is presented along with explanations of both streamflow-data collection and methods for estimating streamflow characteristics at gaged and ungaged sites. Mountain ranges separate the major drainage basins and have a significant effect on the quantity of precipitation and the volume of runoff that occurs in Wyoming. Perennial streams that originate in the mountains provide the most dependable source of runoff; streams that originate in the plains and deserts generally are intermittent or ephemeral and have extended periods of no flow. Streamflow data for several hundred gaged sites in the State are available for engineering and management purposes. When gaged data are not available, methods for estimating streamflow characteristics are needed. Methods presented in this report for estimating streamflow characteristics have been improved over previous methods through the use of refined analytical techniques and an updated data base. Peak-flow characteristics and mean annual runoff at ungaged sites can be estimated by using regression equations, with either basin characteristics or channel width being independent variables. Log-linear regression equations are used for estimating streamflow characteristics in the mountains; whereas, curvilinear equations of double-exponential form were determined to be more appropriate than log-linear relations for depicting peak flows in the plains and deserts. (USGS)

Water-Resources Investigations Report↗
USGS1996

Thickness of unconsolidated deposits in the Puget Sound lowland, Washington and British Columbia

The Puget-Willamette Lowland is located in western Washington, western Oregon, and a small part of southwestern British Columbia, Canada. The Puget-Willamette Lowland study area is composed of two distinct subareas, the Puget Sound Lowland and the Willamette Lowland. This report presents the results of mapping the thickness of the unconsolidated deposits in the Puget Sound Lowland. The thickness of the unconsolidated deposits ranges from a discontinuous veneer in areas of bedrock outcrop to more than 3,600 feet. Available information shows that the unconsolidated deposits are thickest in the Fraser-Whatcom, Everett, Seattle, and Tacoma Basins. The mapped thickness of the unconsolidated deposits in the Tacoma Basin is probably underestimated because of the scarcity of wells penetrating the full thickness of the unconsolidated deposits and the lack of sufficient marine-seismic data.

British Columbia, Washington↗
USGS2003

Water-quality characteristics of urban storm runoff at selected sites in East Baton Rouge Parish, Louisiana, February 1998 through April 2002

Water was sampled at four watersheds for continued evaluation of urban storm runoff in East Baton Rouge Parish, Louisiana, during February 1998 through April 2002. Eighteen samples were collected from four watersheds representing land uses characterized predominantly as established commercial, industrial, new commercial, and residential. Results of water-quality analyses enabled calculation of event-mean concentrations and estimated annual contaminant loads and yields of storm runoff from nonpoint sources for 12 water-quality properties and constituents. The following water-quality data are reported: physical and chemical-related properties, fecal coliform and enterococci bacteria, major inorganic ions, nutrients, trace elements, and organic compounds. The residential land-use is the largest of the watersheds (550 acres), which resulted in high estimated annual contaminant loads compared to other watersheds for 8 of the 12 water-quality properties and constituents. This may indicate that the size of the watershed and runoff from residences with their associated contaminants had substantial effects on annual loads within this land use. The industrial land-use area had the highest estimated annual contaminant loads for metals, followed by the residential landuse area. However, when comparing yields among the watersheds, the industrial watershed had the highest yield for 9 of the 12 water-quality properties and constituents, whereas the residential watershed had the lowest yield for 7 of the 12. The industrial watershed yielded more metals per acre per year than any other watershed. Zinc yields were 2.71 pounds per acre per year from the industrial watershed, compared to 0.35 pounds per acre per year from the residential watershed, which was the lowest of all the watersheds. Lead concentrations exceeded the U.S. Environmental Protection Agency Maximum Contaminant Level of 15 micrograms per liter for drinking water standards in 10 of 18 samples. Low-level concentrations of mercury were detected twice at both the new commercial and residential sites, with all concentrations at or just above reporting limits. The average dissolved phosphorus concentrations from each land use were two to four times higher than the U.S. Environmental Protection Agency criterion of 0.05 milligrams per liter. Diazinon, which is widely used as a general-purpose insecticide for lawns and gardens, was detected in all 18 samples. The maximum diazinon concentration detected, 2.7 micrograms per liter, was from the residential site. Malathion, another insecticide used on lawns, gardens, and plants, was also detected at least once from each site, but all concentrations were below the minimum detection limit of 0.1 micrograms per liter.

Loiusiana↗
USGS2001

Composition and Distribution of Streambed Sediments in the Penobscot River, Maine, May 1999

Sediment samples were collected and geophysical surveys were run along 50 miles of the Penobscot River, Maine, in the spring of 1999 to produce maps that describe the composition and distribution of streambed sediments for selected areas in the river channel. The objective of the sediment survey was to locate areas along the river where fine-grained, easily transportable sediment types were deposited between Old Town and Medway, Maine. These data can be used to design future sediment-sampling programs to assess the quality of streambed sediments and evaluate the health of the Penobscot River. This report describes the results of the sediment survey and the methods used to collect, analyze, and interpret the data used to create maps of streambed-sediment types in the study area. Deposits of fine-grained sediments (mud and sand) are scattered along the shorelines of the mainland and the islands and at the downstream ends of islands and at the mouths of brooks and streams. The most extensive depositional areas were found in the Mattaseunk Dam impoundment near Medway. The main areas of the river channel consist primarily of gravel, sand, and rock.

Water-Resources Investigations Report↗
USGS2002

Prediction of velocities for a range of streamflow conditions in Pennsylvania

A regression equation that is used nationwide to predict traveltime in streams during periods of low and moderate flow was developed by H.E. Jobson in 1996. Because none of the data used in the development of the equation were from streams in Pennsylvania, velocities for low and moderate flows predicted by the equation were compared to velocities measured during time-of-travel studies on the Susquehanna, Delaware, and Lehigh Rivers. Although these comparisons showed good agreement, a similar comparison using velocities for higher flows indicated an overestimate by this regression equation. Because of the need for a method of computing traveltimes for periods of high flows, a new regression equation was developed using data from three sources: (1) time-of-travel studies conducted at low and moderate flow, (2) slop-area measurements of flood flows, and (3) velocities of the 100-year floodway as reported in various flood-insurance studies. The new regression equation can be used for predicting velocities associated with flows up to the 100-year flood for Pennsylvania streams. It has standard errors of estimate of 0.18 feet per second, 0.37 feet per second; and 0.31 feet per second, for time-of-travel studies in the Susquehanna, Delaware, and Lehigh Rivers, respectively. The standard error of estimate is 1.71 feet per second for velocities determined from the slope-area measurements and 1.22 feet per second for velocities determined from the flood-insurance studies.

Water-Resources Investigations Report↗
USGS1998

Extreme precipitation depths for Texas, excluding the Trans-Pecos region

The U.S. Geological Survey, in cooperation with the Texas Department of Transportation, conducted a study of extreme precipitation depths for various durations and storm areas for Texas, excluding the Trans-Pecos region. The extreme precipitation depth is an estimate, from documented storms, of the largest precipitation depth expected to occur over a given area. The extreme precipitation depth exceeds the precipitation depth associated with recurrence intervals greater than 100 years. Storm durations of 1, 2, 3, 4, 5, and 6 days were investigated for this report. The extreme precipitation depth for a particular area is estimated from an “extreme precipitation curve” (an upper limit or envelope curve developed from graphs of extreme precipitation depths for each climatic region). The extreme precipitation curves were determined using precipitation depth-duration information from a subset (24 “extreme” storms) of 213 “notable” storms documented throughout Texas. The extreme precipitation curves can be used to estimate extreme precipitation depth for a particular area. The extreme precipitation depth represents a limiting depth, which can provide useful comparative information for more quantitative analyses.

Texas↗
USGS2000

A field guide for the assessment of erosion, sediment transport, and deposition in incised channels of the southwestern United States

Deeply incised channels, commonly called arroyos, are a typical feature of the dry alluvium-filled valleys of the southwestern United States. Unlike many geological processes that operate over millions of years, the formation of many miles of arroyos is one that took place in a little more than a century. Most arroyos in the region began to form in the late 19th century. Because dry landscapes change so quickly, they present society with special problems. Rapid expansion of channels by headcut migration, deepening, and widening causes loss of productive agricultural and commercial lands and threatens infrastructure such as roads, bridges, and buildings. High rates of sedimentation shorten the life of reservoirs, clog culverts, and fill stream channels to the extent that they can no longer contain streamflow within their banks. This report presents an explanation of erosional and depositional processes in desert landscapes, especially those characterized by incised channels, for the use of those who use, manage, and live on such lands. The basic principles of erosion, sediment transport, and deposition are presented including the formation of sediment, the forces that erode and transport it, the forces that resist its erosion and transport, and the conditions that cause it to be deposited. The peculiarities of sedimentation processes in the Southwest include the infrequent and variable precipitation, the geological setting, and the sparseness of vegetation. A classification system for incised channels that is intended for users who do not necessarily have a background in fluvial hydrology has been developed and is presented in this report. The classification system is intended to enable a user to classify a reach of channel quickly on the basis of field observations. The system is based on the shape and condition of channels and on the sedimentation processes that are predominantly responsible for those conditions. Because those processes are controlled by environmental factors operating on the entire drainage basin, classification of channels can provide land managers and users with an understanding of what areas are likely to be most susceptible to erosion or the effects of high sedimentation rates and under what conditions they are most likely to occur.

Water-Resources Investigations Report↗
USGS1984

Statistical models for estimating flow characteristics of Michigan streams

Multiple-regression equations were developed to estimate flow characteristics at ungaged sites. Several readily measureable basin characteristics and an areal adjustment factor are required in the equations. Equations have been prepared to estimate mean and mean monthly flow, flow duration, low flow, peak flow, and flood volume. The precision of the flow estimate varies with the flow characteristic being estimated, and the basin characteristics at the site of interest. Mean and mean monthly flow characteristics have the lowest standard error while the peak flow and low flow characteristics have the highest standard errors. Sites that have basin characteristics similar to the basin characteristics used to develop the regression equations can be estimated more precisely. Confidence limits can be computed about the estimate using information included in this report. Five regions were designated in Michigan to account for the areal variation in the standard error of regression equations. Increased gaging activity in regions having higher standard errors may provide the greatest potential for increasing the precision of regional transfer of flow information provided .by regression equations. Accordingly, additional continuous-record stations may be most useful in region 3 for reducing the standard error of mean and mean monthly flow equations. Additional partial-record stations may be most beneficial in region 4 for reducing the standard error of low flow and peak-flow regression equations.

Michigan↗
USGS2001

Detection and measurement of land subsidence using Global Positioning System and interferometric synthetic aperture radar, Coachella Valley, California, 1996-98

Land subsidence associated with ground-water-level declines has been recognized as a potential problem in Coachella Valley, California. Since the early 1920s, ground water has been a major source of agricultural, municipal, and domestic supply in the valley, resulting in water-level declines as large as 15 meters (50 feet) through the late 1940s. In 1949, the importation of Colorado River water to the lower Coachella Valley began, resulting in a reduction in ground-water pumping and a recovery of water levels from the 1950s through the 1970s. Since the late 1970s, the demand for water in the valley has exceeded the deliveries of imported surface water, again resulting in increased pumping and ground-water-level declines. The magnitude and temporal occurrence of land subsidence in the lower Coachella Valley are not well known; data are sparse and accuracy varies. Also, the area is tectonically active and has subsided during the past several million years, which further complicates interpretations of the data. Land-surface-elevation data have been collected by many agencies using various methods and different geographic scales; because of this, the -150 millimeters (-0.5 foot) of subsidence determined for the southern parts of the valley for 1930-96 may have a possible error of plus or minus (?)90 millimeters (?0.3 foot). The location, extent, and magnitude of vertical land-surface changes from 1996 to 1998 were determined using Global Positioning System (GPS) and interferometric synthetic aperture radar (InSAR) methods. GPS measurements for 14 monuments in the lower Coachella Valley indicate that the vertical land-surface changes from 1996 to 1998 ranged from -13 to -67 millimeters ? 40 millimeters (-0.04 to -0.22 foot ?0.13 foot). Changes at seven of the monuments exceeded the measurement error of ?40 millimeters (?0.13 foot), which indicates that small amounts of land subsidence occurred at these monuments between 1996 and 1998. Some of the water levels measured in wells near several of these monuments during 1996-98 were the lowest water levels in the recorded histories of the wells. The possible relation between the stresses caused by historically low water levels and the measured vertical changes in land surface suggests that the preconsolidation stress of the aquifer system may have been exceeded during this period and that subsidence may be permanent. Comparisons of several paired monuments and wells indicated that the relation between short-term ground-water-level changes and vertical changes in land surface in the lower Coachella Valley is not clearly defined. Results of InSAR measurements made between 1996 and 1998 indicate that vertical changes in land surface, ranging from about -20 to -70 millimeters ? 5-10 millimeters (-0.07 to -0.23 foot ? 0.02-0.03 foot), occurred in three areas of the Coachella Valley--near Palm Desert, Indian Wells, and Lake Cahuilla. The areas of subsidence near Palm Desert and Indian Wells coincide with areas of substantial ground-water production during 1996-98. The Coachella Valley Water District reported that they had no ground-water production wells in the Lake Cahuilla area but that there may be private production wells in the area. Production from these wells or possibly tectonic activity may be contributing to or causing the subsidence. The geodetic network used for the GPS measurements described in this report covers the area from the Salton Sea on the south to just northwest of Indio. The maps processed using InSAR overlap the part of the geodetic network west of Coachella and north of Lake Cahuilla, and include the Palm Desert area. Both methods of measuring vertical land-surface changes, GPS and InSAR, were used to characterize vertical land-surface changes from the Palm Desert area to the Salton Sea. Because InSAR produces more spatially detailed data over large areas, it generally was useful where vertical land-surface changes were previously unrecognized, such as the

California↗
USGS1989

Flood of September 7-9, 1987, in Lexington and Richland counties in the vicinity of Saint Andrews Road and Irmo, South Carolina

Localized heavy rainfall on September 7, 1987, in Lexington and Richland Counties, South Carolina, caused severe flooding in the basins of Kinley Creek, Rawls Creek, and Stoop Creek, in the vicinity of Saint Andrews Road and the town of Irmo, South Carolina. The flooding damaged homes, furnishings, and landscaping. Rainfall, peak discharges, high-water elevations, and frequency relations of rainfall and discharge are tabulated and plotted for selected streams. The rain was most intense in the area along Rawls Creek, R-2 (tributary to Rawls Creek), Koon Branch (tributary to Rawls Creek), and the upper part of Kinley Creek. A rainfall of about 5.5 inches in 3 hours, which has a recurrence interval in excess of 100 years, was reported by local residents along these streams. High-water marks are presented in this report for Stoop Creek, Kinley Creek, K-1 (tributary to Kinley Creek), K-2 (tributary to Kinley Creek), unnamed tributary to Kinley Creek, Lowery Creek (tributary to Kinley Creek), Rawls Creek, R-2 (tributary to Rawls Creek), and Koon Branch (tributary to Rawls Creek). Peak discharges at the most downstream sites on Rawls Creek and Koon Branch had recurrence intervals of 75 years and 60 years, respectively. Peak discharges on Kinley Creek varied from 20 to 25 years north of K-1 basin to less than 10 years at K-1. The Stoop Creek basin had a recurrence interval of 10 years. (USGS)

South Carolina↗
USGS1986

Measurement of scour-depth near bridge piers

River-bed scour is a major source of damage to bridge piers and bridge abutments. When scour depth exceeds design limits, the supporting material around the footings is washed away and the structure becomes unstable. Equations for predicting scour-depth show a significant lack of agreement so portable equipment for measuring scour is needed. This report discusses the design of an instrumented, unmanned boat that (a) can be launched and controlled from a bridge and (b) can be maneuvered in flood flows that reach velocities of 15 feet per second. Calculations indicate the battery-powered propulsive system alone will weigh about 300 pounds and that the craft must be about 15-feet long. Because a free-running craft will be undesirably heavy and large, other methods of obtaining scour data are proposed. A tethered craft fitted with a controllable rudder and some methods of measuring scour at a point are presented for future study and development.

Water-Resources Investigations Report↗