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At least 577 records · Page 32Linked to original sources
USGS2023

Generalized additive model estimation of no-flow fractions and L-moments to support flow-duration curve quantile estimation using selected probability distributions for bay and estuary restoration in the Gulf States

Censored and uncensored generalized additive models (GAMs) were developed using streamflow data from 941 U.S. Geological Survey streamflow-gaging stations (streamgages) to predict decadal statistics of daily streamflow for streams draining to the Gulf of Mexico. The modeled decadal statistics comprise no-flow fractions and L-moments of logarithms of nonzero streamflow for six decades (1950–2009). These statistics represent metrics of decadal flow-duration curves (dFDCs) derived from about 10 million daily mean streamflows. The L-moments comprise the mean, coefficient of L-variation, and the third through fifth L-moment ratios. The GAMs were fit to the statistics from 941 streamgages and 2,750 streamgage-decades by using watershed properties such as basin area and slope, decadal precipitation and temperature, and decadal values of flood storage and urban development percentages. The GAMs then estimated decadal statistics for 9,220 prediction locations (stream reaches) coincident with outlets of level-12 hydrologic unit codes. Both entire dataset (whole model) and leave-one-watershed-out model results are reported. No-flow fractions are censored data, and Tobit extensions to GAMs were used to model ephemeral streamflow conditions. Conversely, uncensored GAMs were used for estimation of the L-moments. The GAMs are shown, by coverage probabilities, to construct reliable 95-percent prediction limits. An example shows how no-flow fractions and L-moments may be used to approximate dFDCs by using selected probability distributions (mathematical formulas) including the asymmetric exponential power, generalized normal, and kappa distributions.

Alabama, Arkansas, Florida, Georgia, Kentucky, Lou↗
USGS1982

Flow model of the Hudson River estuary from Albany to New Hamburg, New York

A one-dimensional transient-flow-simulation model was developed to represent a 76-mile reach of the tidal Hudson River between Albany and New Hamburg. In this reach, the direction of flow reverses four times daily as a result of tidal influence; this produces complex current patterns and retards the rate at which the river can flush out pollutants. In the model, the reach studied is treated as two subreaches to incorporate differences in channel conditions and to simplify model calibration. This report includes all stage (water-level) and discharge data that were used to calibrate and verify the model and compares the model results with measured data. The model accurately simulated observed flows, but further calibration based upon additional flow measurements would improve simulation of the flow magnitude and phasing of the tide reversal under low-flow conditions. The model can be used to calculate instantaneous stage, velocity, and discharge for any location in the reach and can also be used to calculate net volume flux between tide reversals.

New York↗
USGS1989

Effects of river discharge and high-tide stage on salinity intrusion in the Weeki Wachee, Crystal, and Withlacoochee River estuaries, southwest Florida

The Weeki Wachee, Crystal, and Withlacoochee Rivers are coastal streams flowing into the Gulf of Mexico that may be affected by either future surface water or groundwater withdrawals. Reduction of river discharge will affect the upstream extent of saltwater intrusion in the rivers; however, under certain reduced low-flow discharges, the estimated change in upstream extent of saltwater intrusion is on the order of several tenths of a mile and frequently is within the range of predicted error. Data on flow, tides, and salinity describe the physical characteristics of the Weeki Wachee, Crystal, and Withlacoochee River systems. Vertical and longitudinal salinity profiles indicate that salinity of the rivers increases downstream and varies substantially at any given location. The Weeki Wachee River system is the best mixed of the three. The Crystal River system exhibited the next best mixed system, and the Withlacoochee River system exhibited the most variation in its salinity regime. The daily maximum upstream extent of salinity intrusion is described by multiple linear-regression analysis based on daily mean streamflow of each river and high-tide stage of the gulf. The equations are used to show the effects of discharge on the daily maximum upstream extent of salinity intrusion in the rivers.

Florida↗
USGS1989

A vertically averaged spectral model for tidal circulation in estuaries

A frequency dependent computer model based on the two-dimensional vertically averaged shallow-water equations is described for general purpose application in tidally dominated embayments. This model simulates the response of both tides and tidal currents to user-specified geometries and boundary conditions. The mathematical formulation and practical application of the model are discussed in detail. Salient features of the model include the ability to specify: (1) stage at the open boundaries as well as within the model grid, (2) velocities on open boundaries (river inflows and so forth), (3) spatially variable wind stress, and (4) spatially variable bottom friction. Using harmonically analyzed field data as boundary conditions, this model can be used to make real time predictions of tides and tidal currents. (USGS)

Water-Resources Investigations Report↗
USGS1989

Flow and hydraulic characteristics of the Knik-Matanuska River estuary, Cook Inlet, southcentral Alaska

A study of the riverine-estuarine reach of the Knik and Matanuska Rivers provided flow and hydraulic data for use in the design of additional bridges over the rivers. Hydraulic analysis is complicated because: (1) the lower reaches of the rivers merge in a complex system of interconnected channels; and (2) this reach is subject to unsteady flow conditions resulting from a semidiurnal tide wave propagated up the channel through Knik Arm from Cook Inlet, whose tidal range is among the largest in the world. Analysis of flows for the Knik River is further complicated by the historic formation and outburst flooding of glacier-dammed Lake George in the Upper Knik River basin. Peak flows on the Knik River due to breakout floods were as much as seven times greater than peak flows of non-breakout floods. The U.S. Geological Survey 's branch-network flow model was used to simulate flows within the study reach. For the Knik River, simulated flows were within 10% of measured values in most cases. The model was also used to simulate the flow, stage, and velocity that would be expected in the various channels under different bridge configurations.

Alaska↗