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R.T. Milhous

Publications and source records attributed to R.T. Milhous.

7 recordsLinked to original sources
USGS2012

Changes in the substrate of rivers in historic mining districts

The restoration of rivers in watersheds with historic mining districts has become a topic of interest during the last decade. Rivers restoration in these areas is difficult because the mines and mills can be scattered over a wide area and often small. Many have also been abandoned. This paper presents two substrate related factors that are important in the evaluation of river restoration alternatives in watersheds with significance impacts from mines and mills most of which are old and abandoned. The two factors are 1) changes in the size distribution and specific weights of the substrate, and 2) the changes in quality of the interstecial waters caused by metals associated with the tailings in the substrate. The most important impacts of tailings from mills may be on the physical characteristics of the substrate (porosity) and on the quality of the pore waters. The measurements presented in this paper do show significant variation in the porosity in gravel bed rivers and in the quality of the pore waters. Copyright ASCE 2004.

Conference Paper↗
USGS2005

Climate change and changes in sediment transport capacity in the Colorado Plateau, USA

Information is presented on changes in the sediment transport capacity of streams of the Colorado Plateau region of the United States. The changes in transport capacity may be due to changes in climate. Changes in the ability of three rivers in the Colorado Plateau to transport sediment were investigated (Paria River at Lees Ferry, Arizona; Sevier River at Hatch, Utah; and Little Colorado at Woodruff, Arizona) using an index to sediment transport potential (or capacity) of the rivers. The index is called a Sediment Transport Capacity Index (STCI). The parameters in the index are calibrated to measured sediment concentrations. Other investigators have postulated that there have been three climate regimes in the Colorado Plateau during the 20th century: 1905-1941, 1942-1977 and 1978-1998. Time series analyses of the STCI showed reasonably clearly that there was a change in the climate about 1941 and a high probability of a change about 1923-1929. The STCI time series for the Sevier River had the expected pattern because the STCI increased in the years following 1997 nearly to the pre-1942 values from lower 1942-1977 values. The Little Colorado River showed a similar pattern, but not nearly to the magnitude suggested by the change in precipitation. The STCI for the Paria River essentially did not change. Changes in sediment transport also are investigated in the lower San Juan River where alterations in the sediment balance of the river may be due to variations in the character of summer precipitation.

Conference Paper↗
USGS2004

Mixing physical habitat and streamflow time series analysis

Four observations from two case studies are presented: physical habitat analysis of the Virgin River in southwestern Utah and upper Animas Basin in southwestern Colorado. The Virgin River is usually considered a sand bed river. Cross-sectional measurements, made at three streamflows, show there was considerable change in the channel between the times of the three sets of measurements. First observation: it is important to keep the three sets of data as individual data sets. Second observation: the channel index is not fixed in a river with a moveable-bed and changes affect understanding of the aquatic system. The Animas River has a wide range of streamflows and high metals toxicity. Both winter and spring discharges may limit trout populations. Third observation: (from Animas River) habitat time series analysis should be done with a model that specifically links physical habitat relations and streamflows. Fourth observation: annual time series of habitat suitability considering metals toxicity can be generated. Considering the third and fourth observation together leads to the secondary observation that the hydraulic and stream flow conditions that favor one species may not be as good for the species favored by the water quality conditions.

Hydroécologie Appliquée↗
USGS2004

Physical habitat and sediment in the lower Virgin River

The Virgin River in southwestern Utah and adjacent Arizona and Nevada is habitat for a number of endangered and threatened species of fish. The river also has significant loads of sediment that change the characteristic of the stream channel with time. The Virgin River transports large quantities of sand. Some sections of the river store the sand in the stream bed following a high stream flow event; the sediment is then removed by lower streamflows that can cause a wave of sand to pass through river channels in other sections of the river. The Hurricane Bridge on the Virgin River had a sand wave that passed through the channel during a low flow event that followed a high flow event. This paper demonstrates that antecedent conditions are important in the analysis of physical habitat in sand-bed rivers because the relation between the streamflows and habitat will change depending on these antecedent conditions.

Conference Paper↗
USGS2003

Time series analysis and the analysis of aquatic and riparian ecosystems

Time series analysis of physical instream habitat and the riparian zone is not done as frequently as would be beneficial in understanding the fisheries aspects of the aquatic ecosystem. This paper presents two case studies have how time series analysis may be accomplished. Time series analysis is the analysis of the variation of the physical habitat or the hydro-period in the riparian zone (in many situations, the floodplain).

Book↗
USGS2002

Measurement of the bed material of gravel-bed rivers

The measurement of the physical properties of a gravel-bed river is important in the calculation of sediment transport and physical habitat values for aquatic animals. These properties are not always easy to measure. One recent report on flushing of fines from the Klamath River did not contain information on one location because the grain size distribution of the armour could not be measured on a dry river bar. The grain size distribution could have been measured using a barrel sampler and converting the measurements to the same as would have been measured if a dry bar existed at the site. In another recent paper the porosity was calculated from an average value relation from the literature. The results of that paper may be sensitive to the actual value of porosity. Using the bulk density sampling technique based on a water displacement process presented in this paper the porosity could have been calculated from the measured bulk density. The principle topics of this paper are the measurement of the size distribution of the armour, and measurement of the porosity of the substrate. The 'standard' method of sampling of the armour is to do a Wolman-type count of the armour on a dry section of the river bed. When a dry bar does not exist the armour in an area of the wet streambed is to sample and the measurements transformed analytically to the same type of results that would have been obtained from the standard Wolman procedure. A comparison of the results for the San Miguel River in Colorado shows significant differences in the median size of the armour. The method use to determine the porosity is not 'high-tech' and there is a need improve knowledge of the porosity because of the importance of porosity in the aquatic ecosystem. The technique is to measure the in-situ volume of a substrate sample by measuring the volume of a frame over the substrate and then repeated the volume measurement after the sample is obtained from within the frame. The difference in the volumes is the volume of the sample.

Conference Paper↗