Geology topics

Research about Umpqua River Basin

Source-linked reports with geographic coverage including Umpqua River Basin.

4 recordsLinked to original sources

USGS2010

Channel change and bed-material transport in the Umpqua River basin, Oregon

The Umpqua River drains 12,103 km 2 of western Oregon, heading in the Cascade Range and draining portions of the Klamath Mountains and Coast Range before entering the Pacific Ocean. Above the head of tide, the Umpqua River, along with its major tributaries, the North and South Umpqua Rivers, flows on a mixed bedrock and alluvium bed, alternating between bedrock rapids and intermittent, shallow gravel bars composed of gravel to cobble-sized clasts. These bars have been a source of commercial aggregate since the mid-twentieth century. Below the head of tide, the Umpqua River contains large bars composed of mud and sand. Motivated by ongoing permitting and aquatic habitat concerns related to instream gravel mining on the fluvial reaches, this study evaluated spatial and temporal trends in channel change and bed-material transport for 350 km of river channel along the Umpqua, North Umpqua, and South Umpqua Rivers. The assessment produced (1) detailed mapping of the active channel, using aerial photographs and repeat surveys and (2) a quantitative estimation of bed-material flux that drew upon detailed measurements of particle size and lithology, equations of transport capacity, and a sediment yield analysis. Bed-material transport capacity estimates at 45 sites throughout the South Umpqua and mainstem Umpqua Rivers for the period 1951–2008 result in wide-ranging transport capacity estimates, reflecting the difficulty of applying equations of bed-material transport to a supply-limited river. Median transport capacity values calculated from surface-based equations of bedload transport for each of the study reaches provide indications of maximum possible transport rates and range from 8,000 to 27,000 metric tons/yr for the South Umpqua River and 20,000 to 82,000 metric tons/yr for the mainstem Umpqua River upstream of the head of tide; the North Umpqua River probably contributes little bed material. A plausible range of average annual transport rates for the South and mainstem Umpqua Rivers, based on bedload transport capacity estimates for bars with reasonable values for reference shear stress, is between 500 and 20,000 metric tons/yr. An empirical bed-material yield analysis predicts 20,000–50,000 metric tons/yr on the South Umpqua River and mainstem Umpqua River through the Coast Range, decreasing to approximately 30,000 metric tons/yr at the head of tide. Surveys of individual mining sites in the South Umpqua River indicate minimum local bed-material flux rates that are typically less than 10,000 metric tons/yr but that range up to 30,600 metric tons/yr in high-flow years. On the basis of all of these analyses, actual bedload flux in most years is probably less than 25,000 metric tons/yr in the South Umpqua River and Umpqua Rivers, with the North Umpqua River probably contributing negligible amounts. For comparison, the estimated annual volume of commercial gravel extraction from the South Umpqua River between 2001 and 2004 ranged from 610 to 36,570 metric tons, indicating that historical instream gravel extraction may have been a substantial fraction of the overall bedload flux.

Oregon↗

USGS1996

Assessment of water quality, nutrients, algal productivity, and management alternatives for low-flow conditions, South Umpqua River basin, Oregon, 1990-92

This report is an evaluation of the effects of nutrient loading on water quality in the South Umpqua River Basin. The study was done by the U.S. Geological Survey in cooperation with Douglas County, Oregon. Five wastewater-treatment plants were shown to contribute less than 15 percent of the flow, but more than 90 percent of the nitrogen and phosphorus, in the South Umpqua River during low streamflows in summer. These nutrient inputs were associated with, and largely responsible for, the dense growth of periphytic algae that covered the rocky channel and produced biomass values as large as 340 grams of ash-free dry weight per square meter. The nighttime respiration of periphytic algae caused violations of the Oregon water-quality standard, which requires a dissolved oxygen concentration of at least 90 percent of saturation, at most sites along the South Umpqua River. Photosynthesis by algae during daylight resulted in many exceedances of the Oregon pH standard of 8.5. Net productivity, calculated from hourly measurements of dissolved oxygen concentrations, was as much as 3.8 grams of oxygen per square meter per day. The magnitude of productivity increased with increases in dissolved inorganic nitrogen concentration and load. The large amount of nutrient uptake by algae resulted in lowered nutrient concentrations downstream from nutrient point sources. Management alternatives for the South Umpqua River Basin include several methods to reduce nutrient concentrations and loads. The reduction of dissolved-inorganic-nitrogen and soluble- reactive-phosphorus loads from wastewater- treatment-plant effluent would reduce the frequency of violations of water-quality standards. Flow augmentation probably would decrease water-quality problems in the river, but it is difficult to predict the magnitude of the effects of increased velocity and decreased temperature on algal growth. Land application and storage of wastewater-treatment-plant effluent during the summer months would reduce the input of nutrients from point sources. Three exceedances of the Oregon standard for fecal coliform of 200 colonies per 100 milliliters were associated with large streamflows, suggesting that nonpoint sources affect the river during periods of high runoff. Fecal-streptococcus counts were larger than historical values and require confirmation. Ammonia from wastewater-treatment-plant effluent, high pH values, and high temperatures present a potential for chronic ammonia toxicity in the lower reaches of the South Umpqua River; however, actual violations of standards for chronic concentrations were not detected because of diel fluctuations in pH and water temperature.

Oregon↗

USGS1975

Sediment yields of streams in the Umpqua River Basin, Oregon

This report summarizes sediment data collected at 11 sites in the Umpqua River basin from 1956 to 1973 and updates a report by C. A. Onions (1969) of estimated sediment yields in the basin from 1956-67. Onions' report points out that the suspended-sediment data, collected during the 1956-67 period, were insufficient to compute reliable sediment yields. Therefore, the U.S, Geological Survey, in cooperation with Douglas County, collected additional data from 1969 to 1973 to improve the water discharge-sediment discharge relationships at these sites. These data are published in "Water resources data for Oregon, Part 2, Water quality records," 1970 through 1973 water years. In addition to the 10 original sites, data were collected during this period from the Umpqua River near Elkton station, and a summary of the data for that station is included in table 1.

Oregon↗

USGS1969

Sediment Transport in Streams in the Umpqua River Basin, Oregon

This report presents tables of suspended-sediment data collected from 1956 to 1967 at 10 sites in the Umpqua River basin. Computations based on these data indicate that average annual suspended-sediment yields at these sites range from 137 to 822 tons per square mile. Because available data for the Umpqua River basin are generally inadequate for accurate determinations of sediment yield and for the definition of characteristics of fluvial sediments, recommendations are made for the collection and analysis of additional sediment data.

Oregon↗