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Randy H. Host

Publications and source records attributed to Randy H. Host.

4 recordsLinked to original sources
USGS2005

Hydrology, geomorphology, and flood profiles of Lemon Creek, Juneau, Alaska

Lemon Creek near Juneau, Alaska has a history of extensive gravel mining, which straightened and deepened the stream channel in the lower reaches of the study area. Gravel mining and channel excavation began in the 1940s and continued through the mid-1980s. Time sequential aerial photos and field investigations indicate that the channel morphology is reverting to pre-disturbance conditions through aggradation of sediment and re-establishment of braided channels, which may result in decreased channel conveyance and increased flooding potential. Time sequential surveys of selected channel cross sections were conducted in an attempt to determine rates of channel aggradation/degradation throughout three reaches of the study area. In order to assess flooding potential in the lower reaches of the study area the U.S. Army Corps of Engineers Hydrologic Engineering Center River Analysis System model was used to estimate the water-surface elevations for the 2-, 10-, 25-, 50-, and 100-year floods. A regionally based regression equation was used to estimate the magnitude of floods for the selected recurrence intervals. Forty-two cross sections were surveyed to define the hydraulic characteristics along a 1.7-mile reach of the stream. High-water marks from a peak flow of 1,820 cubic feet per second, or about a 5-year flood, were surveyed and used to calibrate the model throughout the study area. The stream channel at a bridge in the lower reach could not be simulated without violating assumptions of the model. A model without the lower bridge indicates flood potential is limited to a small area.

Scientific Investigations Report↗
USGS2004

Baseline Characteristics of Jordan Creek, Juneau, Alaska

Anadromous fish populations historically have found healthy habitat in Jordan Creek, Juneau, Alaska. Concern regarding potential degradation to the habitat by urban development within the Mendenhall Valley led to a cooperative study among the City and Borough of Juneau, Alaska Department of Environmental Conservation, and the U.S. Geological Survey, that assessed current hydrologic, water-quality, and physical-habitat conditions of the stream corridor. Periods of no streamflow were not uncommon at the Jordan Creek below Egan Drive near Auke Bay stream gaging station. Additional flow measurements indicate that periods of no flow are more frequent downstream of the gaging station. Although periods of no flow typically were in March and April, streamflow measurements collected prior to 1999 indicate similar periods in January, suggesting that no flow conditions may occur at any time during the winter months. This dewatering in the lower reaches likely limits fish rearing and spawning habitat as well as limiting the migration of juvenile salmon out to the ocean during some years. Dissolved-oxygen concentrations may not be suitable for fish survival during some winter periods in the Jordan Creek watershed. Dissolved-oxygen concentrations were measured as low as 2.8 mg/L at the gaging station and were measured as low as 0.85 mg/L in a tributary to Jordan Creek. Intermittent measurements of pH and dissolved-oxygen concentrations in the mid-reaches of Jordan Creek were all within acceptable limits for fish survival, however, few measurements of these parameters were made during winter-low-flow conditions. One set of water quality samples was collected at six different sites in the Jordan Creek watershed and analyzed for major ions and dissolved nutrients. Major-ion chemistry showed Jordan Creek is calcium bicarbonate type water with little variation between sampling sites.

Open-File Report↗
USGS1999

Hydrology, geomorphology, and flood profiles of the Mendenhall River, Juneau, Alaska

Water-surface-profile elevations for the 2-, 20-, 25-, 50-, and 100-year floods were computed for the Mendenhall River near Juneau, Alaska, using the U.S. Army Corps of Engineers Hydrologic Engineering Center River Analysis System model. The peak discharges for the selected recurrence intervals were determined using the standard log-Pearson type III method. Channel cross sections were surveyed at 60 locations to define hydraulic characteristics over a 5.5-mile reach of river beginning at Mendenhall Lake outlet and extending to the river mouth. A peak flow of 12,400 cubic feet per second occurred on the Mendenhall River on October 20, 1998. This discharge is equivalent to about a 10-year flood on the Mendenhall River and floodmarks produced by this flood were surveyed and used to calibrate the model. The study area is currently experiencing land-surface uplift rates of about 0.05 foot per year. This high rate of uplift has the potential to cause incision or downcutting of the river channel through lowering of the base level. Vertical datum used in the study area was established about 37 years before the most recent surveys of river-channel geometry. The resulting difference between land-surface elevations and sea level continues to increase. Continuing incision of the river channel combined with increased land-surface elevations with respect to sea level may result in computed flood profiles that are higher than actual existing conditions in the tidally influenced reach of the river.

Alaska↗