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J. E. Costa

Publications and source records attributed to J. E. Costa.

28 records · Page 2Linked to original sources
USGS1988

The potential for catastrophic dam failure at Lake Nyos maar, Cameroon

The upper 40 m of Lake Nyos is bounded on the north by a narrow dam of poorly consolidated pyroclastic rocks, emplaced during the eruptive formation of the Lake Nyos maar a few hundred years ago. This 50-m-wide natural dam is structurally weak and is being eroded at an uncertain, but geologically alarming, rate. The eventual failure of the dam could cause a major flood (estimated peak discharge, 17000 m3/s) that would have a tragic impact on downstream areas as far as Nigeria, 108 km away. This serious hazard could be eliminated by lowering the lake level, either by controlled removal of the dam or by construction of a 680-m-long drainage tunnel about 65 m below the present lake surface. Either strategy would also lessen the lethal effects of future massive CO2 gas releases, such as the one that occurred in August 1986. ?? 1988 Springer-Verlag.

Bulletin of Volcanology↗
USGS1988

Evaluation of the flood hydrology in the Colorado Front Range using precipitation, streamflow, and paleoflood data for the Big Thompson River basin

A multidisciplinary study of precipitation and streamflow data and paleohydrologic studies of channel features was made to analyze the flood hydrology of foothill and mountain streams in the Front Range of Colorado, with emphasis on the Big Thompson River basin, because conventional hydrologic analyses do not adequately characterize the flood hydrology. In the foothills of Colorado, annual floodflows are derived from snowmelt at high elevations in the mountain regions, from rainfall at low elevation in the plains or plateau regions, or from a combination of rain falling on snow or mixed population hydrology. Above approximately 7,500 ft, snowmelt dominates; rain does not contribute to the flood potential. Regional flood-frequency relations were developed and compared with conventional flood-estimating technique results, including an evaluation of the magnitude and frequency of the probable maximum flood. Evaluation of streamflow data and paleoflood investigations provide an alternative for evaluating flood hydrology and the safety of dams. The study indicates the need for additional data collection and research to understand the complexities of the flood hydrology in mountainous regions, especially its effects on flood-plain management and the design of structures in the flood plain. (USGS)

Water-Resources Investigations Report↗
USGS1987

Hydraulics and basin morphometry of the largest flash floods in the conterminous United States

The maximum rainfall-runoff floods measured by indirect methods in small basins (0.39-370 km 2 ) in the conterminous United States are examined. This analysis identified twelve floods that were the largest ever measured. These floods all occurred in semiarid to arid areas. For eleven of the twelve largest rainfall-runoff floods measured in small basins by the slope-area method, values of hydraulic depth; hydraulic radius; width-depth ratio; n value; mean velocity; velocity-head coefficient; Froude number; water-surface, energy, and channel slopes; shear stress; and unit stream power are tabulated. Estimated composite n values weighted by subsection conveyance range from 0.028 to 0.048 with a mean of 0.038. Mean velocities ranged from 3.47 to 9.97 m s −1 . Froude numbers ranged from 0.81 to 2.49, with 9 of 12 floods having values greater than 1.00. Water-surface, energy, and channel slopes vary considerably for each flood. Energy slope always was less than water-surface slope by values of 1–104%. Channel slope was greater than energy slope in eight floods. Shear stresses ranged between 61 and 855 N m −2 , and unit stream power from 212 to 8131 w m −1 . Floods in these small basins produced shear stresses and unit stream powers several hundred times greater than floods in large rivers. Floods on other small streams, with smaller unit discharges, produced greater shear stresses and stream powers. This indicates that the force of a flood is controlled by the depth-slope product, not absolute discharge. In the twelve watersheds studied, basin relief ranged from 165 to 1280 m, elongation ratios ranged from 0.55 to 0.80, the number of first-order streams (basin magnitude) ranged from 10 to 4297, drainage density ranged from 4.1 to 10.9 km km −2 , basin slope ranged from 0.0043 to 0.2486, relief ratio ranged from 0.0097 to 0.34, ruggedness number ranged from 0.69 to 7.17, and first-order channel frequency ranged from 5.1 to 38.6 km −2 . Elongation ratios were larger, and drainage density and first-order channel frequency lower, than other small flash-flood prone basins in the United States. These twelve basins have neither the most favorable morphometric characteristics which contribute to flash-flood peaks, nor did the storms causing these flash floods have the greatest short-duration intensities. Maximum flood peaks originate from an optimal combination of basin morphology and physiography, and storm intensity.

conterminous United States↗
USGS1987

A comparison of the largest rainfall-runoff floods in the United States with those of the People's Republic of China and the world

The maximum historic rainfall-runoff floods measured in the United States, the People's Republic of China and the world all plot close to a smooth curve of drainage area versus discharge. In the United States, the possibility that flood peaks were overestimated and the closeness of these peaks to the probable maximum floods suggest that this limiting curve of maximum floods will not significantly change position with more data. Data for future floods that plot above this curve need to be examined carefully. The most likely interpretations for new data points above the curve would be the confusion of a mud or debris flow with a water-dominated flood, or the damming of channels by debris or a landslide and subsequent bursting. In the United States, excluding Hawaii, the largest measured historic floods in basins less than about 1000 km 2 , all occurred in arid and semi-arid areas. In China, the majority of the largest measured historic floods occurred in the east and southeast in basins on the windward side of mountainous areas, and in locations affected by typhoons. One extraordinary flood that exceeds any other recorded flood in the world for the size of the drainage basin in which it occurred is the New Caledonia flood of December 24, 1981 on the Ouaieme River. Worldwide, the largest measured historic floods occurred primarily between 40°N and 40°S latitude on streams and rivers near coastal areas.

Journal of Hydrology↗
USGS1987

The formation and failure of natural dams

Of the numerous kinds of dams that form by natural processes, dams formed from landslides, glacial ice, and neoglacial moraines present the greatest threat to people and property. The most common types of mass movements that form landslide dams are rock and debris avalanches, rock and soil slumps and slides, and mud, debris, and earth flows. The most common initiation mechanisms for dam-forming landslides are excessive rainfall and snowmelt and earthquakes. Landslide dams can be classified into six categories based on their relation with the valley floor. Type I dams (11%) of the 81 landslide dams around the world that were classifed do not reach from one valley side to the other. Type II dams (44%) span the entire valley flood, occasionally depositing material high up on opposite valley sides. Type III dams (41%) move considerable distances both upstream and downstream from the landslide failure. Type IV dams (1%) are rare and involve the contemporaneous failure of material from both sides of a valley. Type V dams (1%) are also rare, and are created when a single landslide sends multiple tongues of debris into a valley forming two or more landslide dams in the same surfaces, that extend under the stream or valley and emerge on the opposite valley side. Many landslide dams fail shortly after formation. Overtopping is by far the most common cause of failure. Glacial ice dams can produce at least nine kinds of ice-dammed lakes. The most dangerous are lakes formed in main valleys dammed by tributary glaciers. Failure can occur by erosion of a drainage tunnel under or through the ice dam or by a channel over the ice dam. Cold polar ice dams generally drain supraglacially or marginally by downmelting of an outlet channel. Warmer temperate-ice dams tend to fail by sudden englacial or subglacial breaching and drainage. Late neoglacial moraine-dammed lakes are located in steep mountain areas affected by the advances and retreats of valley glaciers in the last several centuries. The most common reported failure mechanism is overtopping and breaching by a wave or series of waves in the lake, generated by icefalls, rockfalls, or snow or rock avalanches. Melting of ice-cores or frozen ground and piping and seepage are other possible failure mechanisms. (Lantz-PTT)

Open-File Report↗
USGS1987

Hydrologic hazards along Squaw Creek from a hypothetical failure of the glacial moraine impounding Carver Lake near Sisters, Oregon

A hydrologic hazard exists that could create a large-magnitude, but short-duration, flood in the Squaw Creek drainage and inundate areas in and around the community of Sisters, Oregon. There is a 1 to 5% probability that Carver Lake, located at elevation 7,800 ft above sea level on the east slope of South Sister mountain, Oregon, could catastrophically empty. At the U.S. Geological Survey gage (14075000) on Squaw Creek between Carver Lake and Sisters, the magnitude of the breakout flood would be 10 times that of a 1% probability meteorological flood. In Sisters, the magnitude of the breakout flood would be about five times that of a 1% probability meteorological flood. Several conditions at Carver Lake indicate the potential hazard: (1) The lake is very deep for its size; the lake contains 740 acre-ft of water and is more than 100 ft deep; (2) There is a probability that a large magnitude avalanche and consequent overtopping of the lake could occur. There are steep slopes of unstable volcanic rock and an extensively cravassed glacier located above the lake; (3) The moraine dam confining the lake is steep-faced, rendering the dam unstable, and unvegetated making it highly erodible; (4) Large amounts of readily erodible material available for transport would increase the magnitude of a large flood and keep the flood from attenuating in the steep reaches of the Squaw Creek channel; (5) and, Geologically, there is a greater than normal possibility for the area to become seismically active. Earthquakes could cause rock and ice to fall into the lake. A one-dimensional unsteady-state streamflow model was used to route a hypothetical flood down the Squaw Creek drainage. This scenario creates a starting hydrograph with a peak of 180,000 cu ft/sec. The ensuing hypothetical flood would incorporate readily erodible debris and sediments in the steep canyons, increasing the total volume of the flood by a factor of two. As the peak emerges from the steeper slopes into a more gently sloping valley 8 miles from the lake, the peak would attenuate to 47,000 cu ft/sec. At the Geological Survey gage at river mile 26.6, the peak would attenuate to 21,000 cu ft/sec. In Sisters on the alluvial fan, at about 20 miles downstream from the lake, the peak would continue to attenuate to 9,800 cu ft/sec. (Lantz-PTT)

Open-File Report↗
USGS1984

Hydrology, geomorphology, and dam-break modeling of the July 15, 1982, Lawn Lake Dam and Cascade Lake Dam failures, Larimer County, Colorado

On July 15, 1982, Lawn Lake Dam, a 26-foot-high earthfill irrigation dam built in 1903 in Rocky Mountain National Park, Colorado, failed, due to piping, releasing 674 acre-feet of water with a peak discharge of 18,000 cubic feet per second down the Roaring River. Three people were killed, and damages were estimated at $31 million. Cascade Lake Dam, downstream from Lawn Lake Dam, subsequently failed as a result of the flood, increasing the peak flow at this point from 7,210 cubic feet per second to 16,000 cubic feet per second. The flood wave took 3.28 hours to travel 12.5 miles to Lake Estes, where all the floodwater was stored. The channel of the Roaring River was scoured as much as 50 feet and widened 300 feet. An alluvial fan of 42.3 acres, containing 10 million cubic feet of material, was deposited at the mouth of the Roaring River, damming the Fall River and forming a 17-acre lake. Various methods were used to indirectly compute peak discharge, attenuation of flow, and flood traveltime. A version of the National Weather Service dam-break flood model was used to evaluate its performance on high-gradient streams, to provide supplemental hydrologic information, and to evaluate various scenarios of dam-break development. (USGS)

Colorado↗
USGS1983

Paleohydraulic reconstruction of flash- flood peaks from boulder deposits in the Colorado Front Range

Nine watersheds in the Colorado Front Range with steep bedrock channels were used to test the accuracy of paleohydraulic reconstruction of large flash floods using boulder deposits. The nine basins consist of eight small ungauged basins ranging in size from 1.6 to 29 km 2 and the Big Thompson River at the mouth of the Big Thompson Canyon, draining 790 km 2 . Between 1923 and 1976, all nine basins had had one catastrophic flash flood, the magnitude of which has been estimated by the conventional slope-area method. In each basin, coarse boulder deposits of the large flash floods were identified, and three axes of the five largest boulders were measured, along with at least two profiles of the valley cross section. A simple arithmetic average of two theoretical and two empirical relationships was used to estimate average flood velocity using boulder size and shape. Average depth was estimated as the arithmetic average of four values computed from the Manning equation, a regression equation for boulder size and unit stream power, a relative smoothness equation, and a modified Shields' relationship. The appropriate flood width for the estimated average depth was found by iteration, using the valley cross sections. The paleohydraulic discharges thus computed generally underestimate conventional slope-area discharge estimates on small streams by as much as 75%, although the average amount is only 28% too low, and the reconstructed discharge in one stream was 31% too large. The Big Thompson River flood of 1976 was overestimated by 76%. Reasons for discrepancy in reconstructed peaks could include (1) the possibility that floods may have been able to move boulders larger than those available to be moved; (2) overestimation of the slope-area discharge because high-water marks were set prior to erosion of the channel; (3) underestimation of original roughness coefficients; and (4) macroturbulent effects during fast, deep flows. The paleohydraulic technique is applied to two other streams in Colorado with sedimentological evidence of large flash floods, but no conventional indirect discharge estimates. A small tributary to the Big Thompson River draining 1.8 km 2 has a paleohydraulic reconstructed flood peak of about 60 m 3 /s from a flood in 1976. Using boulders excavated from a foundation site in Holocene alluvium along Boulder Creek in Boulder, Colorado, a paleohydraulic reconstructed flood peak of between 860 and 1,512 m 3 /s is calculated. This is 1.4 to 2.4 times the magnitude of the estimated 500-yr flood.

Geological Society of America Bulletin↗