Geology topics

Janet H. Curran

Publications and source records attributed to Janet H. Curran.

At least 19 recordsLinked to original sources

USGS2026

Understanding flooding and channel dynamics along the Taiya River: Providing context for resource management

Flooding and channel change in the Taiya River Basin in recent decades have directly affected park infrastructure and cultural resources. The complexities of flooding and channel change are compounded by the changing sediment and flow regime from a changing climate and shrinking glaciers, which will continue to drive dynamic riverine change. Streamflow data and geomorphic interpretation helped us place these events in context to inform decision making that takes dynamic natural processes into account.

Alaska↗

USGS2025

Selected special conditions affecting peak streamflow and extreme floods in Alaska through water year 2022

The U.S. Geological Survey, in cooperation with the Alaska Department of Transportation and Public Facilities, inventoried selected special conditions for annual peak flows and identified extreme floods at streamgages in Alaska through water year 2022 to facilitate hydrologic analysis. Special conditions identified from U.S. Geological Survey gaging records and basin characteristics included regulation and diversion, urbanization, indeterminate drainage areas, drainage areas less than the minimum used in regional analyses, glacial lake outburst floods, other outburst floods, and snowmelt floods. For peak flows that occurred during calendar years 1980–2019, an atmospheric river dataset was used to identify atmospheric river presence or absence on the dates peak flows occurred. Extreme floods (defined as peak flows exceeding the 1-percent annual exceedance probability flood magnitude or an empirical measure of relative magnitude using Creager’s coefficient C) were identified and associated with flood-generating mechanisms using the other inventoried special conditions and other information. The gaging record contained glacial lake outburst floods at 15 streamgages and other types of outburst floods at 10 streamgages. Non-outburst peak flows in Alaska resulted from a mixture of rainfall and melt-based flood-generating mechanisms in all but the most rain-dominated seasonal flow regime. Melt-based flood-generating mechanisms included snowmelt, high-elevation snow and ice melt, or rain-on-snow events. Atmospheric rivers were common in Alaska and conterminous basins in Canada, occurring in that region on 67 percent of the days in the calendar year 1980–2019 period. Atmospheric rivers were more common on the days of peak flows and even more common on the days of non-outburst extreme floods. The percentage of days when an atmospheric river was present increased to 78 percent for the days of peak flows in that period and to 83 percent for the days of non-outburst extreme floods in that period. Of 149 extreme floods in the gaging record, 38 were generated by outburst floods. Of the non-outburst extreme floods, 72 percent were generated by rainfall and 26 percent were generated by melt-based processes or a combination of rainfall and melt-based processes. Flood-generating mechanisms could not be determined for the final 2 percent of the non-outburst extreme floods because the month and day of the peak flows were unknown and no other information was available. Secondary factors strongly associated with extreme floods included antecedent rain and streamflow conditions and warm storm conditions that produced rain instead of snow or generated snowmelt.

Alaska↗

USGS2025

Streamflow response to glacier mass loss varies with basin precipitation across Alaska

Diminishing glaciers affect streamflow, and given the extent of glaciers in Alaska and adjacent Canada, continued glacier mass loss is likely to have profound effects on ecosystems sensitive to runoff. The effects of glacier mass loss on streamflow are likely to vary across the wide ranges of basin size, glacier cover, and precipitation in this region. In this study, we use U.S. Geological Survey (USGS) streamflow data with satellite-based glacier volume change estimates to quantify how glacier mass loss subsidized streamflow over the 2000–2019 period for 116 glacierized basins. We examine interannual variability in that subsidy at three USGS-monitored glaciers to explore the ability of the subsidy to buffer streamflow derived solely from precipitation. We found the relative importance of percent glacier cover on streamflow magnitude increases in drier basins. In the driest basins, glaciers produced 40 times greater percent glacier mass loss subsidies to streamflow for the percent glacier cover compared to the wettest basins. While the subsidy from glacier mass loss buffers interannual variability in streamflow to varying degrees, it can also increase streamflow variability. Smaller amounts of percent glacier cover are needed to produce summer-melt-dominated seasonal flow regimes in drier basins than in wetter basins. Decreasing glacier cover will eventually decrease summer streamflow, increasing spring streamflow in drier basins, and attenuating seasonality with increasing spring and autumnal streamflow in wetter basins. Quantifying the downstream effects of continued glacier mass loss without the computational expense of a hydrological model is broadly applicable in this changing climate.

Alaska↗

USGS2024

Repeated coseismic uplift of coastal lagoons above the Patton Bay Splay Fault System, Montague Island, Alaska, USA

Coseismic slip on the Patton Bay splay fault system during the 1964 M w 9.2 Great Alaska Earthquake contributed to local tsunami generation and vertically uplifted shorelines as much as 11 m on Montague Island in Prince William Sound (PWS). Sudden uplift of 3.7–4.3 m caused coastal lagoons along the island's northwestern coast to gradually drain. The resulting change in depositional environment from marine lagoon to freshwater muskeg created a sharp, laterally continuous stratigraphic contact between silt and overlying peat. Here, we characterize the geomorphology, sedimentology, and diatom ecology across the 1964 earthquake contact and three similar prehistoric contacts within the stratigraphy of the Hidden Lagoons locality. We find that the contacts signal instances of abrupt coastal uplift that, within error, overlap the timing of independently constrained megathrust earthquakes in PWS—1964 Common Era, 760–870 yr BP, 2500–2700 yr BP, and 4120–4500 yr BP. Changes in fossil diatom assemblages across the inferred prehistoric earthquake contacts reflect ecological shifts consistent with repeated draining of a lagoon system caused by >3 m of coseismic uplift. Our observations provide evidence for four instances of combined megathrust-splay fault ruptures that have occurred in the past ∼4,200 years in PWS. The possibility that 1964-style combined megathrust-splay fault ruptures may have repeated in the past warrants their consideration in future seismic and tsunami hazards assessments.

Alaska↗

USGS2022

Evaluating hydrologic region assignment techniques for ungaged basins in Alaska, USA

Building continental-scale hydrologic models in data-sparse regions requires an understanding of spatial variation in hydrologic processes. Extending these models to ungaged locations requires techniques to group ungaged locations with gaged ones to make process importance and model parameter transfer decisions to ungaged locations. This analysis (1) tested the utility of fundamental streamflow statistics (FDSS) in defining hydrologic regions across Alaska, USA; (2) evaluated if the hydrologic regions represented different hydrologic processes; and (3) tested the ability of random forest and direct assignment techniques, informed by statistically estimated FDSS (FDSSest) and basin characteristics (BCs), to correctly assign ungaged locations to hydrologic regions. Six hydrologic regions were identified across the domain using FDSS. Differences in mean flow, phase shift of the seasonal cycle, and skewness were the primary characteristics defining each region. Two regions represented arctic and continental climates, generally in the northern portion of the domain; four regions represented the southern, maritime portion of the domain. Random forest modeling with BCs (67% success rate) outperformed FDSSest (58% success rate) suggesting that no statistically estimated streamflow was needed to assign ungaged locations to a region. For regions with many sites, most region assignment techniques performed similarly. Random forest modeling performance declined when BCs and FDSSest were both used to predict region membership, suggesting FDSSest had little information in addition to BCs. This analysis demonstrated that FDSS-based hydrologic regions discern process differences across a data-sparse and hydrologically diverse landscape. Process importance rankings from random forest-derived BCs provided model-independent information for making modeling decisions.

Alaska↗

USGS2021

Extending seasonal discharge records for streamgage sites on the North Fork Fortymile and Middle Fork Fortymile Rivers, Alaska, through water year 2020

Daily mean discharge records are needed for management of selected streams in the Fortymile River Basin. The U.S. Geological Survey, in cooperation with the U.S. Bureau of Land Management, updated a technique for estimating seasonal (partial year) discharge at two short-record streamgage sites in the basin and evaluated the accuracy of the estimates. Daily mean discharge values were estimated for May 15–September 30, 1976–82 and 2006–18, for U.S. Geological Survey streamgage sites 15330000 (North Fork Fortymile River above Middle Fork near Franklin, Alaska) and 15331000 (Middle Fork Fortymile River near mouth near Chicken, Alaska). Relations between discharge for each study streamgage and an index streamgage on the main-stem Fortymile River (15348000, Fortymile River near Steele Creek, Alaska) for concurrent seasonal periods in 2019 and 2020 were developed using the maintenance of variance extension type 3 (MOVE.3) record extension technique. The MOVE.3 regressions were used to estimate daily mean discharges at the study streamgage sites for the selected season for the longer period of record of the index streamgage. Additionally, estimated records were generated from the regressions for the concurrent seasonal periods to evaluate the accuracy of the record extension techniques. The modified Nash-Sutcliffe efficiency coefficients for the estimated records were 0.53 for the North Fork Fortymile River (15330000) and 0.70 for the Middle Fork Fortymile River (15331000) streamgages.

Alaska↗

USGS2021

Identification of seasonal streamflow regimes and streamflow drivers for daily and peak flows in Alaska

Alaska is among northern high‐latitude regions where accelerated climate change is expected to impact streamflow properties, including seasonality and primary flow drivers. Evaluating changes to streamflow, including flood characteristics, across this large and diverse environment can be improved by identifying the distribution and influence of flow drivers. Using metrics of mean monthly streamflow data from 253 streamgages, seasonal flow regimes were clustered to guide identification of seasonal‐flow drivers and form hydrologic groups for identification of peak‐flow populations. Nine seasonally distinct subclasses described variability within three classes dominated by (mostly fall) rainfall, (spring) snowmelt, and (summer) high‐elevation melt. The most glacierized basins exclusively grouped into high‐elevation melt subclasses, and less glacierized basins sometimes exhibited seasonal patterns aligned with rainfall‐ and snowmelt‐dominated regimes. Peak‐flow populations varied by subclass from dominant rainfall or dominant snowmelt to mixed rainfall‐snowmelt or mixed rainfall, snowmelt, and high‐elevation melt. Within subclasses, rainfall generated higher mean peak flows (relative to mean annual flow) than snowmelt or high‐elevation melt. Seasonal flow regimes showed clear but complex associations with basin characteristics, primarily elevation and winter temperature, and with geographic location. These dependencies provided elevation‐based analogies for changes associated with warming and insights for seasonal flow regime prediction and hydrologic region delineation. These results provide a spatially comprehensive perspective on seasonal streamflow drivers across Alaska from historical data and serve as an important historical basis for analysis.

Alaska↗

USGS2020

Hydrology and geomorphology of the Taiya River near the West Creek Tributary, southeast Alaska

The Taiya River flows through the Chilkoot Trail Unit of Klondike Gold Rush National Historical Park in southeast Alaska, which was founded to preserve cultural and historical resources and further understanding of natural processes active in the surrounding coastal-to-subarctic basin. Riverine processes exert an important influence on ecologically important boreal toad ( Anaxryus boreas boreas ), salmon [chum salmon ( Oncorhynchus keta ), pink salmon ( O. gorbushca ), and coho salmon ( O. kisutch )], and eulachon ( Thaleichthys pacificus ) habitats, erosion of the historic ghost town of Dyea and other cultural and historical artifacts, and recreational opportunities in the lower 7.5 kilometers (km) of the Taiya River valley bottom. Recurrent consideration of hydroelectric development in West Creek upstream of the park since the 1980s has included proposals for damming and diverting West Creek, which could alter the delivery of water and sediment to this section of the Taiya River. To improve understanding of the hydrologic dependence of park resources for the purposes of guiding effective monitoring and conservation, this study, conducted by the U.S. Geological Survey in cooperation with the National Park Service, used a review of hydrologic data, collection of discrete suspended sediment data, geomorphic mapping, and analysis of historical aerial and ground photographs in a reconnaissance of formative geomorphic processes and hydrologic conditions in the lower 7.5 km of the Taiya River valley bottom. Streamflow and suspended sediment data collected at the U.S. Geological Survey streamgages on the Taiya River and West Creek, combined with historical data, document conditions consistent with streams draining strongly glacierized basins in Alaska. Suspended sediment concentrations from samples collected concurrently over six varying flow levels during 2017–18 ranged from 6 to 284 milligrams per liter (mg/L) for the Taiya River and 13 to 162 mg/L for West Creek, which are similar to or slightly higher than historical values. For the common period of record (1970–77), correlation of daily mean discharge between the two streams was strongest (Pearson’s r = 0.97) during the prolonged May–October high-flow season and weakest ( r = 0.90) during the November–April low-flow season, when West Creek daily mean discharge was proportionally higher. For the Taiya River, streamflow data compared between the available periods of record (1970–77 and 2004–17) showed no decadal-scale patterns in mean annual discharge but did show a shift toward an earlier spring snowmelt pulse. Notable flooding in the Taiya River Basin includes glacial lake outburst floods from the Nourse River valley prior to and during the 1897–98 Gold Rush, a 2002 glacial lake outburst flood from the West Creek valley, and a 1967 rainfall-generated flood. Geomorphic mapping identified four categories of surfaces in the valley bottom—active main stem, abandoned main stem, alluvial fans, and emergent tidal surfaces. Using the maps, main-stem surfaces were subdivided into age categories to identify channel migration patterns from prior to 1940s to 2018. The valley bottom is dominated by active or abandoned channels of the Taiya River except at the extensive low-angle West Creek fan. The active main stem presently supports a mostly single-thread channel with bars and a few sloughs, but the channel actively moved and sometimes was braided within multiple, wider unvegetated corridors in 1894 and earlier. An inventory of 29 off-main-stem channels identified for the study indicates that abandoned main stem channels provide local topographic lows that can intercept groundwater or sustain tributary flow, facilitating the formation of most nonestuarine wetlands in the valley and sustaining important boreal toad breeding habitat. Within the active main stem corridor, the channel has episodically built and reworked meanders and bars, eroding more than one-half of the historic Dyea townsite, in response to glacially controlled delivery of water and sediment, flooding, inputs from West Creek, local features including large woody debris and beaver dams, and rapid uplift from isostatic rebound. West Creek has constructed a large, persistent fan, provoked kilometer-scale Taiya River channel change near the confluence, constructively added to high-season streamflow that affects Taiya River channel migration capacity, disproportionately contributed early-season streamflow, and possibly contributed to groundwater levels in the valley bottom. The progressive narrowing and stability of the main stem corridor, possibly a result of reduction in the magnitude or frequency of glacial lake outburst floods or glacial sediment delivery to streams, indicates less active future reworking of abandoned main-stem surfaces or regeneration of wetland features. The fluvial history of the Taiya River valley bottom collectively indicates continued channel change within a limited corridor, relative stability in wetland locations but uncertainty in stability of groundwater supply to them, and channel incision and extension in response to uplift.

Alaska↗

USGS2020

Extending seasonal discharge records for streamgage sites on the North Fork Fortymile and Middle Fork Fortymile Rivers, Alaska, through water year 2019

Daily mean discharge values were estimated for May 20–September 30 for 1976–82 and 2006–18 for the U.S. Geological Survey North Fork Fortymile River and Middle Fork Fortymile River streamgage sites in Alaska. A relation between study streamgage discharge and discharge for an index streamgage on the main-stem Fortymile River for a concurrent period in 2019 was developed using the maintenance of variance extension type 3 (MOVE.3) record extension technique. The relation for North Fork Fortymile River discharges incorporated a 1-day-earlier offset to index streamgage discharges. No offset was applied to the index streamgage discharges for use with the Middle Fork Fortymile River discharges. The developed MOVE.3 regressions were used to estimate daily mean discharges at the study streamgage sites during the study season for the longer period of record of the index streamgage. The modified Nash-Sutcliffe efficiency coefficients for the estimated records were 0.38 and 0.63 for the North Fork Fortymile River and Middle Fork Fortymile River streamgages, respectively.

Alaska↗

USGS2017

Glacial conditioning of stream position and flooding in the braid plain of the Exit Glacier foreland, Alaska

Flow spilling out of an active braid plain often signals the onset of channel migration or avulsion to previously occupied areas. In a recently deglaciated environment, distinguishing between shifts in active braid plain location, considered reversible by fluvial processes at short timescales, and more permanent glacier-conditioned changes in stream position can be critical to understanding flood hazards. Between 2009 and 2014, increased spilling from the Exit Creek braid plain in Kenai Fjords National Park, Alaska, repeatedly overtopped the only access road to the popular Exit Glacier visitor facilities and trails. To understand the likely cause of road flooding, we consider recent processes and the interplay between glacier and fluvial system dynamics since the maximum advance of the Little Ice Age, around 1815. Patterns of temperature and precipitation, the variables that drive high streamflow via snowmelt, glacier meltwater runoff, and rainfall, could not fully explain the timing of road floods. Comparison of high-resolution topographic data between 2008 and 2012 showed a strong pattern of braid plain aggradation along 3 km of glacier foreland, not unexpected at the base of mountainous glaciers and likely an impetus for channel migration. Historically, a dynamic zone follows the retreating glacier in which channel positions shift rapidly in response to changes in the glacier margin and fresh morainal deposits. This period of paraglacial adjustment lasts one to several decades at Exit Glacier. Subsequently, as moraine breaches consolidate and lock the channel into position, and as the stream regains the lower-elevation valley center, upper-elevation surfaces are abandoned as terraces inaccessible by fluvial processes for timescales of decades to centuries. Where not constrained by these terraces and moraines, the channel is free to migrate, which in this aggradational setting generates an alluvial fan at the breach of the final prominent moraine. The position of this fan is glacially conditioned but the process of migration of the braided channels across it is not. This broad perspective on channel controls identifies incipient avulsion into the roadside forest as part of a long-term fan-building process independent from changes in streamflow or sediment load.

Alaska↗

USGS2016

Estimating flood magnitude and frequency at gaged and ungaged sites on streams in Alaska and conterminous basins in Canada, based on data through water year 2012

Estimates of the magnitude and frequency of floods are needed across Alaska for engineering design of transportation and water-conveyance structures, flood-insurance studies, flood-plain management, and other water-resource purposes. This report updates methods for estimating flood magnitude and frequency in Alaska and conterminous basins in Canada. Annual peak-flow data through water year 2012 were compiled from 387 streamgages on unregulated streams with at least 10 years of record. Flood-frequency estimates were computed for each streamgage using the Expected Moments Algorithm to fit a Pearson Type III distribution to the logarithms of annual peak flows. A multiple Grubbs-Beck test was used to identify potentially influential low floods in the time series of peak flows for censoring in the flood frequency analysis. For two new regional skew areas, flood-frequency estimates using station skew were computed for stations with at least 25 years of record for use in a Bayesian least-squares regression analysis to determine a regional skew value. The consideration of basin characteristics as explanatory variables for regional skew resulted in improvements in precision too small to warrant the additional model complexity, and a constant model was adopted. Regional Skew Area 1 in eastern-central Alaska had a regional skew of 0.54 and an average variance of prediction of 0.45, corresponding to an effective record length of 22 years. Regional Skew Area 2, encompassing coastal areas bordering the Gulf of Alaska, had a regional skew of 0.18 and an average variance of prediction of 0.12, corresponding to an effective record length of 59 years. Station flood-frequency estimates for study sites in regional skew areas were then recomputed using a weighted skew incorporating the station skew and regional skew. In a new regional skew exclusion area outside the regional skew areas, the density of long-record streamgages was too sparse for regional analysis and station skew was used for all estimates. Final station flood frequency estimates for all study streamgages are presented for the 50-, 20-, 10-, 4-, 2-, 1-, 0.5-, and 0.2-percent annual exceedance probabilities. Regional multiple-regression analysis was used to produce equations for estimating flood frequency statistics from explanatory basin characteristics. Basin characteristics, including physical and climatic variables, were updated for all study streamgages using a geographical information system and geospatial source data. Screening for similar-sized nested basins eliminated hydrologically redundant sites, and screening for eligibility for analysis of explanatory variables eliminated regulated peaks, outburst peaks, and sites with indeterminate basin characteristics. An ordinary least‑squares regression used flood-frequency statistics and basin characteristics for 341 streamgages (284 in Alaska and 57 in Canada) to determine the most suitable combination of basin characteristics for a flood-frequency regression model and to explore regional grouping of streamgages for explaining variability in flood-frequency statistics across the study area. The most suitable model for explaining flood frequency used drainage area and mean annual precipitation as explanatory variables for the entire study area as a region. Final regression equations for estimating the 50-, 20-, 10-, 4-, 2-, 1-, 0.5-, and 0.2-percent annual exceedance probability discharge in Alaska and conterminous basins in Canada were developed using a generalized least-squares regression. The average standard error of prediction for the regression equations for the various annual exceedance probabilities ranged from 69 to 82 percent, and the pseudo-coefficient of determination (pseudo-R 2 ) ranged from 85 to 91 percent. The regional regression equations from this study were incorporated into the U.S. Geological Survey StreamStats program for a limited area of the State—the Cook Inlet Basin. StreamStats is a national web-based geographic information system application that facilitates retrieval of streamflow statistics and associated information. StreamStats retrieves published data for gaged sites and, for user-selected ungaged sites, delineates drainage areas from topographic and hydrographic data, computes basin characteristics, and computes flood frequency estimates using the regional regression equations.

Alaska↗

USGS2013

Formation and evolution of valley-bottom and channel features, Lower Deschutes River, Oregon

Primary geologic and geomorphic processes that formed valley-bottom and channel features downstream from the Pelton-Round Butte dam complex are inferred from a canyon-long analysis of feature morphology, composition, location, and spatial distribution. Major controls on valley-bottom morphology are regional tectonics, large landslides, and outsized floods (floods with return periods greater than 1000 yrs), which include the late Holocene Outhouse Flood and several Quaternary landslide dam failures. Floods with a return period on the order of 100 yrs, including historical floods in 1996, 1964, and 1861, contribute to fan building and flood plain formation only within the resistant framework established by the major controls. Key processes in the formation of channel features, in particular the 153 islands and 23 large rapids, include long-term bedrock erosion, outsized floods, and century-scale floods. Historical analysis of channel conditions since 1911 indicates that the largest islands, which are cored by outsized-flood deposits, locally control channel location, although their margins are substantially modified during annual- to century-scale floods. Islands cored by bedrock have changed little. Islands formed by annual- to century-scale floods are more susceptible to dynamic interactions between tributary sediment inputs, mainstem flow hydraulics, and perhaps riparian vegetation. Temporal patterns of island change in response to the sequence of 20th century flooding indicate that many islands accreted sediment during annual- to decadal-scale floods, but eroded during larger century-scale floods. There is, however, no clear trend of long-term changes in patterns of island growth, movement, or erosion either spatially or temporally within the lower Deschutes River.

Oregon↗

USGS2012

Streamflow record extension for selected streams in the Susitna River Basin, Alaska

Daily streamflow records for water years 1950–2010 in the Susitna River Basin range in length from 4 to 57 years, and many are distributed within that period in a way that might not adequately represent long-term streamflow conditions. Streamflow in the basin is affected by the Pacific Decadal Oscillation (PDO), a multi-decadal climate pattern that shifted from a cool phase to a warm phase in 1976. Records for many streamgages in the basin fell mostly within one phase of the PDO, such that monthly and annual statistics from observed records might not reflect streamflow conditions over a longer period. Correlations between daily discharge values sufficed for extending streamflow records at 11 of the 14 streamgages in the basin on the basis of relatively long-term records for one or more of the streamgages within the basin, or one outside the basin, that were defined as index stations. Streamflow at the index stations was hydrologically responsive to glacier melt and snowmelt, and correlated well with flow from similar high-elevation, glaciated basins, but flow in low-elevation basins without glaciers could not be correlated to flow at any of the index stations. Kendall-Theil Robust Line multi-segment regression equations developed for one or more index stations were used to extend daily discharge values to the full 61-year period for all 11 streamgages. Monthly and annual statistics prepared for the extended records show shifts in timing of breakup and freeze-up and magnitude of snowmelt peaks largely predicted by the PDO phase.

Alaska↗

USGS2011

Distribution, persistence, and hydrologic characteristics of salmon spawning habitats in clearwater side channels of the Matanuska River, southcentral Alaska

Turbid, glacially influenced rivers are often considered to be poor salmon spawning and rearing habitats and, consequently, little is known about salmon habitats that do occur within rivers of this type. To better understand salmon spawning habitats in the Matanuska River of southcentral Alaska, the distribution and characteristics of clearwater side-channel spawning habitats were determined and compared to spawning habitats in tributaries. More than 100 kilometers of clearwater side channels within the braided mainstem of the Matanuska River were mapped for 2006 from aerial images and ground-based surveys. In reaches selected for historical analysis, side channel locations shifted appreciably between 1949 and 2006, but the relative abundance of clearwater side channels was fairly stable during the same period. Geospatial analysis of side channel distribution shows side channels typically positioned along abandoned bars at the braid plain margin rather than on bars between mainstem channels, and shows a strong correlation of channel abundance with braid plain width. Physical and geomorphic characteristics of the channel and chemical character of the water measured at 19 side channel sites, 6 tributary sites, 4 spring sites, and 5 mainstem channel sites showed conditions suitable for salmon spawning in side channels and tributaries, and a correlation of side channel characteristics with the respective tributary or groundwater source water. Autumn-through-spring monitoring of intergravel water temperatures adjacent to salmon redds (nests) in three side channels and two tributaries indicate adequate accumulated thermal units for incubation and emergence of salmon in side channels and relatively low accumulated thermal units in tributaries.

Alaska↗

USGS2011

Geomorphology and bank erosion of the Matanuska River, southcentral Alaska

Bank erosion along the Matanuska River, a braided, glacial river in southcentral Alaska, has damaged or threatened houses, roadways, and public facilities for decades. Mapping of river geomorphology and bank characteristics for a 65-mile study area from the Matanuska Glacier to the river mouth provided erodibility information that was assessed along with 1949-2006 erosion to establish erosion hazard data. Braid plain margins were delineated from 1949, 1962, and 2006 orthophotographs to provide detailed measurements of erosion. Bank material and height and geomorphic features within the Matanuska River valley (primarily terraces and tributary fans) were mapped in a Geographic Information System (GIS) from orthophotographs and field observations to provide categories of erodibility and extent of the erodible corridor. The braid plain expanded 861 acres between 1949 and 2006. Erosion in the highest category ranged from 225 to 1,043 feet at reaches of bank an average of 0.5 mile long, affecting 8 percent of the banks but accounting for 64 percent of the erosion. Correlation of erosion to measurable predictor variables was limited to bank height and material. Streamflow statistics, such as peak streamflow or mean annual streamflow, were not clearly linked to erosion, which can occur during the prolonged period of summer high flows where channels are adjacent to an erodible braid plain margin. The historical braid plain, which includes vegetated braid plain bars and islands and active channels, was identified as the greatest riverine hazard area on the basis of its historical occupation. In 2006, the historical braid plain was an average of 15 years old, as determined from the estimated age of vegetation visible in orthophotographs. Bank erosion hazards at the braid plain margins can be mapped by combining bank material, bank height, and geomorphology data. Bedrock bluffs at least 10 feet high (31 percent of the braid plain margins) present no erosion hazard. At unconsolidated banks (63 percent of the braid plain margins), erosion hazards are great and the distinction in hazards between banks of varying height or geomorphology is slight.

Alaska↗

USGS2009

Baseline Channel Geometry and Aquatic Habitat Data for Selected Streams in the Matanuska-Susitna Valley, Alaska

Small streams in the rapidly developing Matanuska-Susitna Valley in south-central Alaska are known to support anadromous and resident fish but little is known about their hydrologic and riparian conditions, or their sensitivity to the rapid development of the area or climate variability. To help address this need, channel geometry and aquatic habitat data were collected in 2005 as a baseline of stream conditions for selected streams. Three streams were selected as representative of various stream types, and one drainage network, the Big Lake drainage basin, was selected for a systematic assessment. Streams in the Big Lake basin were drawn in a Geographic Information System (GIS), and 55 reaches along 16 miles of Meadow Creek and its primary tributary Little Meadow Creek were identified from orthoimagery and field observations on the basis of distinctive physical and habitat parameters, most commonly gradient, substrate, and vegetation. Data-collection methods for sites at the three representative reaches and the 55 systematically studied reaches consisted of a field survey of channel and flood-plain geometry and collection of 14 habitat attributes using published protocols or slight modifications. Width/depth and entrenchment ratios along the Meadow-Little Meadow Creek corridor were large and highly variable upstream of Parks Highway and lower and more consistent downstream of Parks Highway. Channel width was strongly correlated with distance, increasing downstream in a log-linear relation. Runs formed the most common habitat type, and instream vegetation dominated the habitat cover types, which collectively covered 53 percent of the channel. Gravel suitable for spawning covered isolated areas along Meadow Creek and about 29 percent of Little Meadow Creek. Broad wetlands were common along both streams. For a comprehensive assessment of small streams in the Mat-Su Valley, critical additional data needs include hydrologic, geologic and geomorphic, and biologic data, in particular the contribution of ground water and lakes to streamflow, water quality, flood plain connectivity, and surficial geology.

Scientific Investigations Report↗

USGS2007

Hydrology and Flood Profiles of Duck Creek and Jordan Creek Downstream from Egan Drive, Juneau, Alaska

Hydrologic and hydraulic updates for Duck Creek and the lower part of Jordan Creek in Juneau, Alaska, included computation of new estimates of peak streamflow magnitudes and new water-surface profiles for the 10-, 50-, 100-, and 500-year floods. Computations for the 2-, 5-, 10-, 25-, 50-, 100-, 200-, and 500-year recurrence interval flood magnitudes for both streams used data from U.S. Geological Survey stream-gaging stations weighted with regional regression equations for southeast Alaska. The study area for the hydraulic model consisted of three channels: Duck Creek from Taku Boulevard near the stream's headwaters to Radcliffe Road near the end of the Juneau International Airport runway, an unnamed tributary to Duck Creek from Valley Boulevard to its confluence with Duck Creek, and Jordan Creek from a pedestrian bridge upstream from Egan Drive to Crest Street at Juneau International Airport. Field surveys throughout the study area provided channel geometry for 206 cross sections, and geometric and hydraulic characteristics for 29 culverts and 15 roadway, driveway, or pedestrian bridges. Hydraulic modeling consisted of application of the U.S. Army Corps of Engineers' Hydrologic Engineering Center River Analysis System (HEC-RAS) for steady-state flow at the selected recurrence intervals using an assumed high tide of 20 feet and roughness coefficients refined by calibration to measured water-surface elevations from a 2- to 5-year flood that occurred on November 21, 2005. Model simulation results identify inter-basin flow from Jordan Creek to the southeast at Egan Drive and from Duck Creek to Jordan Creek downstream from Egan Drive at selected recurrence intervals.

Scientific Investigations Report↗

USGS2003

Large woody debris and flow resistance in step-pool channels, Cascade Range, Washington

Total flow resistance, measured as Darcy-Weisbach f , in 20 step-pool channels with large woody debris (LWD) in Washington, ranged from 5 to 380 during summer low flows. Step risers in the study streams consist of either (1) large and relatively immobile woody debris, bedrock, or roots that form fixed, or “forced,” steps, or (2) smaller and relatively mobile wood or clasts, or a mixture of both, arranged across the channel by the stream. Flow resistance in step-pool channels may be partitioned into grain, form, and spill resistance. Grain resistance is calculated as a function of particle size, and form resistance is calculated as large woody debris drag. Combined, grain and form resistance account for less than 10% of the total flow resistance. We initially assumed that the substantial remaining portion is spill resistance attributable to steps. However, measured step characteristics could not explain between-reach variations in flow resistance. This suggests that other factors may be significant; the coefficient of variation of the hydraulic radius explained 43% of the variation in friction factors between streams, for example. Large woody debris generates form resistance on step treads and spill resistance at step risers. Because the form resistance of step-pool channels is relatively minor compared to spill resistance and because wood in steps accentuates spill resistance by increasing step height, we suggest that wood in step risers influences channel hydraulics more than wood elsewhere in the channel. Hence, the distribution and function, not just abundance, of large woody debris is critical in steep, step-pool channels.

Washington↗