USGS Washington Water Science Center
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WA250 - New Lakes of North Fork Toutle River - Completed FY1986
Problem - During the eruption of Mt. St. Helens on May 18, 1980 a massive landslide was blasted laterally into the North Fork Toutle River Valley, blocking the flow of several of six tributary streams and thus forming ponds on the debris structure. At the present time all but three of the ponds have either breached through the blocking debris dam or the dams have been breached by the Corps of Engineers. The three remaining lakes are continuing to fill and owing to their ultimate possible size continue to represent potential hazards to citizens and property located downstream. Estimates are that should Coldwater Lake breach at its maximum volume (100,000 acre--feet) it would create a mudflow on the North Fork Toutle twice the size of the one associated with the May 18 eruption.
Objectives - A study of the remaining lakes is proposed that would have as its major objectives for each lake: (1) monitoring the rate of lake filling, (2) estimate the potential for and rate of lake filling, (3) evaluate the potential for debris dam breaching at or prior to filling, and (4) assess the flooding hazard from breaching.
Approach - The rate of lake filling will be monitored by visual sightings of staff gages at each lake. Bubble gages will be installed for continuous records of lake stage. The estimates for the potential of and rate of lake filling will be computed using a water-budget equation. The potential for debris dam failure prior to filling is being evaluated by Geologic Division; factors to be considered will be slope failure, piping, and landslides of earth slopes bordering the lakes. Evaluation of the rate of downcutting and discharge from the lakes should overtopping or piping occur will be made by the WRD using the Survey's Dam Break Flood Forecast Model.
WA247 - Cowlitz River Flood-Wave and Sediment Transport Hydraulics - Completed FY1985
Problem - Since the May 1980 eruption of Mount St. Helens, geometry of subsequent mudflow and sediment deposits in the Cowlitz River has been surveyed more than 26 times to document ongoing physical processes. Initially, the surveys provided data for step-backwater analysis used to estimate flood elevations that might be produced by a major runoff event. After dredging operations began, the purpose became that of providing a chronological record of sediment deposition in the Cowlitz and an indirect record of sediment transport into the Columbia, and detecting any major deterioration in Cowlitz channel flood capacity. All of the survey data thus far collected represent low-flow observations only. Changes in hydraulic parameters occurring during the ascension to, peak, and recision from high flows in this unstable channel are unknown. Knowledge of these changes are required for technically correct hydraulic simulations.
Approach - Each survey will consist of at least one stationed fathometer trace and the determination of water-surface elevations; each sampling will consist of a vertically integrated suspended sediment sample, replicated and one streambed sample at each of three or more verticals, each vertical located near the center of their respective cross-sectional areas. A hydraulic routing model will be calibrated from discharge measurements and used to route the hydrograph of the flood wave downstream from gaging stations to the cross sections, so that river discharge at the cross sections can be determined at any time of survey or sampling.
WA248 - Channel Geomorphology, Sediment Movement, and Channel Changes of Pine and Muddy Rivers - Completed FY1984
Problem - On May 18, 1980, Mount St. Helens erupted after 120 years of dormancy. Channel morphology and runoff characteristics of streams surrounding the volcano have been altered. Although the impact of the initial blast and subsequent ash eruptions have been heaviest to the north, there has also been a significant though less dramatic impact on smaller drainage basins to the east and south of the volcano. Change in the morphology of the channels can be expected to continue in response to the sediment and water moving through the system.
Objectives - To define the existing conditions with respect to channel geometry, hydraulic geometry, and sediment sources and transport characteristics for 6 streams. To the extent possible, the U.S. Geological Survey (USGS) will define the hydraulic and channel geometry sources prior to May 18 in order to assess the immediate impact of the eruption, evaluate processes responsible for observed changes, a compare the magnitude of the initial changes and subsequent rate of change in channel geometry and sedimentation characteristics with other areas of similar process.
Approach - The Survey will study channel geometry and sediment storage at 20 reaches on 6 streams; measure sediment concentration and discharge in the channels; identify sediment sources; describe deposits and processes contributing to channel form and erosion; carry out petrographic analyses of selected suspended sediment, bedload, and bed material samples to examine sources of sediment; and determine the hydraulic geometry and channel geometry relations prior to the eruption from old records and historic data.
WA249 - Photogrammetry of Selected Streams Draining Mt. St. Helens - Completed FY1982
Problem - The eruption of Mt. St. Helens on May 18 materially affected the runoff characteristics of streams draining the mountain. Mud and pyroclastic flows deposited massive amounts of materials in the channels and on the overbanks of the streams draining the northern and eastern flanks of the mountain; the blast leveled approximately 150 square miles of the drainage basins of these streams. Ash fallout up to several feet thick has covered watersheds draining the mountain. The consequences of rainfall, snowmelt, and/or subsequent mudflows in these streams is unknown. Cross-sectional data and contour mapping of these streams are required to help assess the magnitude of the flood hazard.
Objectives - To provide the necessary cross-sectional data and contour mapping for assessing the potential flood hazard for the streams draining Mt. St. Helens.
Approach - National Mapping Division (NMD) is conducting a photogrammetric survey of cross sections using 1:9600 scale photographs. The District will field survey underwater parts of cross sections, bridges/culverts, and about 10% of total cross sections too difficult to photograph. A bathymetric survey will be done in Swift Reservoir, and we will field survey reference points used to measure water levels at the time of photography. Above-water portions of cross sections will be digitized by NMD, below-water parts by the District; these will be meshed by use of a Washington District computer program. Topographic-planimetric or ortho mosaic contour mapping will be done by NMD. The District will perform stepbackwater computation and plotting of elevation profiles corresponding to selected flow magnitudes.
WA246 - The Occurrence, Distribution, and Fate of Organic-Vegetation Decay Products in the Vicinity of Mt. St. Helens - Completed FY1982
Problem - The May 18 eruption of Mt. St. Helens caused massive destruction of the nearby forest lands--forests on the northern slopes were completely pyrolyzed and burned; and a short distance from the mountain trees were uprooted, stripped of bark, branches, and leaves, and buried in hot debris and mud. These buried tree materials are decaying rapidly, producing a thick, black, tar-like substance. Initial analysis of this substance indicates the presence of a large number of organic compounds. We need to document the fate and distribution of these decay products so that we can then determine the potential for downstream health-related problems.
Objectives - To meet the objectives of this study we will locate and sample several different sites where the accelerated decay of trees is evident. We need to document with time the manner in which the decay products change. District staff will comprehensively sample the affected tributaries and the Toutle River to determine the changes which occur from the site of formation to the point of sample collection, the mobility of these organic compounds in the aquatic environment, and the concentration of those compounds. Finally, we need to ascertain, with time, if the compounds moving the aquatic environment are present in the mudflow deposits of the lower Cowlitz River valley.
Approach - Several specific sites which are known to be contributing wood-decay products have been sampled. Other sites will be located and sampled. In addition, Spirit Lake, three-fourths of which is covered with rotting trees, will be sampled. Test holes in the Cowlitz River valley will be sampled to determine if wood-decay compounds are occurring in the ground-water system. The specific sites in the Toutle drainage will be sampled on a bimonthly basis. Only a few representative test wells in the Cowlitz valley will be sampled with this frequency--of course, the occurrence of any compounds will necessitate a more comprehensive ground-water sampling effort.
WA291 - Water-Quality Effects of Pumping from Spirit Lake - Completed FY1983
Problem - To reduce the potential for breakout of Spirit Lake, the Corps of Engineers (COE) has proposed two long-term solutions: (Releasing lake water through outlet channels to South Coldwater Creek or the headwaters of Smith Creek). Both pose serious potential problems. Numerous reports indicate that Spirit Lake water may be of poor quality and contain pathogenic bacteria; therefore, the quality of the receiving stream may be adversely affected.
Approach - A field reconnaissance will be completed to select stream data-collection sites. Data will be collected from Spirit Lake and from sites on each of the potential receiving streams. Discharge measurements will be made at the time of sampling. The physical, chemical, and biological effects of placing Spirit Lake water in receiving streams will be analyzed on the basis of the relative quantities and qualities of the water masses involved.
WA289 - Sediment Transport Model Development and Preliminary Application to the Columbia River - Completed FY1990
Problem - The Washington District needs the ability to model sediment transport, especially in view of the large-scale transport which is taking place from the slopes of Mount St. Helens. However, state-of-the-art in sediment transport modeling is such that results are reliable only within an order of magnitude. It requires a good water routing model; the routing of non-steady state flood phenomena; and the ability to handle complex geometries with constructions, expansions, tributaries, and distributaries.
Objectives - To develop a sediment transport model, or set of compatible models, that allow more comprehensive and accurate modeling than is now possible with existing models.
Approach - We will review existing models and learn of their capabilities and limitations by applying a select few to the lower Columbia River with input of a Cowlitz River mudflow. Desirable features from them will be used in constructing a more refined model suitable for our applications. We will utilize a finite element setting and construct a two-dimensional model to provide detailed results, augmented by a one-dimensional channel model to provide more approximate results faster. The models will then be configured and calibrated to simulate conditions measured in the Toutle River and seen in recent mudflows and floods on the Toutle and Cowlitz Rivers. Results of this investigation will be documented in a Water Resources Investigations report or Professional Paper.
WA283 - Spirit Lake Hazard Monitoring - Completed FY1983
Problem - The threat of catastrophic flooding resulting from the failure of the debris blockage of Spirit Lake requires that a real-time warning and hazard evaluation system be established. The Water Resources Division (WRD), U.S. Geological Survey (USGS), proposes to expand and utilize their Geostationary Operational Environmental Satellite (GOES) telemetry system to detect and monitor such a failure and to assist the National Weather Service (NWS) in providing that warning to State and local emergency agencies.
Objectives - To furnish minute-by-minute data, on a real-time basis, in case of a sudden drop in lake level, and monitor the height of a flood wave downstream from the lake. The data would also be used in conjunction with a dam-break model to estimate the peak discharge resulting from a failure of Spirit Lake blockage.
Approach - Stream and lake stage stations will be constructed by the U.S. Geological Survey and equipped with GOES telemetry units capable of transmitting alert messages at one-minute intervals. These data will be received by USGS (Tacoma and Vancouver) and NWS (Seattle and Portland) on a real-time basis. NWS radio telemetry will also be installed at these stations to provide redundant data in case of failure of the telemetry system. Any sudden, small drop in the level of Spirit Lake will trigger both the NWS and USGS telemetry systems to begin transmitting Spirit Lake level data every minute. The rate of lake level decline versus time will be plotted and compared to curves computed by the dam-break model. These curves will provide an estimate of peak flow resulting from a breach.
WA254 - Effects of Mount St. Helens Eruption on Nearby Lakes - Completed FY1982
Problem - The major eruption of Mount St. Helens on May 18, 1980, dumped tons of mud, logs, and debris into more than 30 near-pristine lakes in the immediate vicinity of the volcano. The physical, chemical, and biological characteristics of lakes in the blast zone have been changed to varying degrees. In time, however, the lakes will recover or return to new states of equilibrium. This situation provides a unique opportunity to study the effects of a major volcanic eruption on alpine lakes and to monitor their eventual recoveries.
Approach - Current conditions will be documented in 5 or 6 lakes in the area immediately north of the volcano, the area of maximum impact. Lakes will be selected to represent conditions ranging from highly impacted to relatively unimpacted. Priority will be given to lakes for which pre-eruption data are available. The lakes will be visited six times per year; at each visit measurements will be made of water transparency, pH, temperature, dissolved oxygen, and chlorophyll a concentration. Samples of the phyloptankton and zooplankton communities will be taken and identified. Samples from both the epilimnion and hypolimnion will be analyzed for about 65 constituents.
WA251 - Toutle River Basin Rainfall-Runoff Sediment Model - Completed FY1982
Problem - The volcanic activity of Mt. St. Helens has resulted in the deposition of large amounts of sediment and ash in the Toutle River basin and in the alteration of the runoff and sediment transport characteristics of the river. Winter precipitation may transport large volumes of sediment through the Toutle basin and subsequently into the already sediment-laden Cowlitz River. This would result in a decreased carrying capacity and an increased potential for flooding. Estimates of daily hourly values for runoff and sediment volumes need to be projected for the Toutle River for various magnitudes of future precipitation so that the effects of inflow to Cowlitz River can be evaluated.
Objectives - The primary objectives of the study are to apply the U.S. Geological Survey (USGS) rainfall-runoff-sediment model to historical data and post-eruption data to obtain estimates of daily and peak runoff/sediment volumes from the Toutle River basin. Preliminary (short-term) estimates of runoff/sediment volumes are needed for immediate emergency planning. A refined (long-term) model is needed to make better estimates for next year's winter precipitation season. The refined model will be calibrated and verified on the basis of rainfall-runoff/sediment data obtained this winter.
Approach - We will collect rainfall-temperature, streamflow, and sediment data at selected sampling sites and begin preliminary configuration of the rainfall-runoff-sediment model to the Toutle basin. We will also alter the daily and hourly computer program so that it can be used in the Toutle basin, estimate model parameters, calibrate and verify the daily and hourly model based on data from September 1972 to June 1979, adjust model parameters to account for post-eruption changes, update and finalize model parameters for use in the 1981-2 winter season.
WA258 - Atmospheric Deposition Program--Acid Rain - Completed FY1981
Problem - A Mt. St. Helens program has been initiated to take advantage of a rare opportunity to measure and document the effects of volcanic emissions on the quality and character or atmospheric deposition. In the State of Washington 12 sites have been established for the collection and monitoring of precipitation chemistry. Currently the largest network of precipitation chemistry in the United States is the National Atmospheric Deposition Program (NADP). There is a need to standardize data-collection and quality-assurance procedures to insure data comparability to NADP.
Objectives - Monitor precipitation chemistry in the State of Washington at seven sites for the purpose of detecting possible effects from Mt. St. Helens volcanic activity using data collection techniques such that the data will be compatible and of utility to the NADP program.
Approach - Data collection procedures will be changed significantly from the technique of employing the double 4-inch plastic collectors on an event only basis. Seven automatic wet-fall dry-fall precipitation collectors and recording rain gages will be installed at selected sites. At each site qualified observers will be trained to obtain an accumulated weekly sample, make field determinations of pH and specific conductance of the sample, process the sample as directed, and send it to the Denver Central Lab.
WA255 - Mount St. Helens Aerial Photography - Completed FY1981
Problem - The eruption of Mount St. Helens on May 18, 1980, significantly affected the topography and, consequently, the hydrology of the surrounding area, particularly the Cowlitz and Toutle River basins. A number of hydrologic investigations have been or will be planned for many of the drainages in the vicinity of the mountain. Common to many of these investigations is a need for accurate, up-to-date cross-section data and topographic contour maps; aerial photography is an integral part of this data collection/mapping effort.
Objectives - To provide repetitive aerial photography suitable for identifying the locations of cross-sections and elevation reference marks to generate stream cross-section data and topographic contour maps using photogrammetry.
Approach - All photography will be taken using a camera with 6-inch focal-length lens at a flight height of 4,800 feet above terrain. The scale of photography is 1:9600 (1 inch = 800 feet).
WA253 - Stage-Discharge Ratings, New Stations on Mount St. Helens Streams - Completed FY1981
Problem - The mudflows that accompanied the eruption of Mt. St. Helens on May 18, 1980 destroyed the continuous-record stream-gaging stations on the Toutle and Cowlitz Rivers. The mudflow also deposited sediment in the channels and on the overbanks, and in some cases scoured the stream channels, thus changing the stage-discharge ratings for those sites. The stations are being replaced and additional new stations installed to monitor the effects of present mudflows and future changes. Data from these stations are being telemetered on a real-time basis for hazard warning. Because changes may occur rapidly, the usual process for rating the stations will not be adequate; without accurate ratings, data may be misinterpreted.
Objectives - To rapidly estimate stage-discharge ratings for new and replaced stream-gaging stations.
Approach - Step-backwater analysis will be applied to data for about 10 cross-sections located about two channel widths apart downstream from each station to be rated. SW elevations will be computed for a range of discharges and a stage-discharge rating drawn. The above-water cross-sections will be obtained from the National Mapping Division (NMD) interpretation of aerial photography and underwaters will be obtained by field survey. Many of the stations are located in areas of sediment deposits and the channels may take several years to fully stabilize. To the extent possible estimated ratings will be verified by discharge measurements as runoff events occur. If major changes in measured ratings are observed, additional photography and step backwater analyses will be obtained.
WA252 - Elevation Profiles for Mudflows in Streams After the May 18 Eruption of Mount St. Helens - Completed FY1981
Problem - The May 18, 1980, eruption of Mt. St. Helens caused mudflows along six major streams--the Cowlitz, Toutle, North Fork Toutle, South Fork Toutle, and Muddy Rivers, and Pine Creek. A number of scientific studies and investigations are planned or underway to document the extent, dynamics, and effects of the mudflows, and many of those studies have certain common data requirements. A project is already in progress to document the elevations of mudflows and the detrimental effects of sediment deposits on flood elevations in the Cowlitz and lower Toutle Rivers. On the other four streams, however, the elevations of the mudflows still need to be determined.
Objectives - To document elevations of high mud marks along both banks of the streams affected by mudflows from the May 18, 1980 eruption of Mt. St. Helens.
Approach - The mudlines left by the flows exceeded recorded high water lines and are generally above the flood plains, in places many tens of feet up on the hillsides, rising and falling around bends and through valley contractions. Because the magnitudes are so great a minimum single-point accuracy of plus or minus 1 foot should provide adequate description of mudline elevations. The mudflow profiles already determined for the Cowlitz and Toutle Rivers are acceptable for this study. Aerial photos at a scale of 1:6000 (taken prior to May 19, 1980) will be used on the North Fork Toutle. Aerial photos taken during June 1980 at 1:9600 will be used for the remaining streams. Western Mapping Center will interpret mudflow peak elevations and digitize the data for computer plotting.