J. Steven Kite

Geomorphic effects of large debris flows on channel morphology at North Fork Mountain, eastern West Virginia, USA

Extreme rainfall in June 1949 and November 1985 triggered numerous large debris flows on the steep slopes of North Fork Mountain, eastern West Virginia. Detailed mapping at four sites and field observations of several others indicate that the debris flows began in steep hillslope hollows, propagated downslope through the channel system, eroded channel sediment, produced complex distributions of deposits in lower gradient channels, and delivered sediment to floodwaters beyond the debris-flow termini. Based on the distribution of deposits and eroded surfaces, up to four zones were identified with each debris flow: an upper failure zone, a middle transport/erosion zone, a lower deposition zone, and a sediment-laden floodwater zone immediately downstream from the debris-flow terminus. Geomorphic effects of the debris flows in these zones are spatially variable. The initiation of debris flows in the failure zones and passage through the transport/erosion zones are characterized by degradation; 2300 to 17 000 m3 of sediment was eroded from these zones. The total volume of channel erosion in the transport/erosion zones was 1·3 to 1·5 times greater than the total volume of sediment that initially failed, indicating that the debris flows were effective erosion agents as they travelled through the transport/erosion zones. The overall response in the deposition zones was aggradation. However, up to 43 per cent of the sediment delivered to these zones was eroded by floodwaters from joining tributaries immediately after debris-flow deposition. This sediment was incorporated into floodwaters downstream from the debris-flow termini causing considerable erosion and deposition in these channels.

Cave sedimentation, genesis, and erosional history in the Cheat River Canyon, West Virginia

A model of cave sedimentation and genesis is used to gain greater resolution and accuracy in the calculation of an incision rate for Cheat River, West Virginia. Maze caves along the river and their primary sediments were created and deposited beneath base level. Single conduit caves are largely unrelated to base level and their sediments are derived from overlying strata. A magnetostratigraphic record is reported for cave sediments within the canyon. The magnetostratigraphy of each sample is plotted versus elevation relative to base level and depositional environment (vadose or phreatic). The resulting chart accurately depicts the range of error associated with using cave sediments as indicators of previous base-level positions. This technique can be applied within any future studies using cave sediments for deriving incision rates of rivers. The calculated incision rate of Cheat River within the study area is between 56.0 and 63.2 mm/k.y.

River-derived slackwater sediments in caves along Cheat River, West Virginia

Abstract The November 1985 Cheat River flood produced overbank, slackwater deposits in caves of the Cheat River canyon. The deposits include loamy silt, loamy sand to very fine sand, and flotsam. Sediments deposited by the November 1985 flood lie within 1 m of the established high water mark and are good indicators of peak stage. Prehistoric overbank, slackwater deposits are present in one cave. These sediments are inferred to be ≥400,000 years old and are, therefore, unrelated to the modern Cheat River. Overbank slackwater deposits are poorly preserved in the examined caves, because cave streams actively remove sediments and the warm, moist environment of the caves fosters decay of woody flotsam. Deposits of the 1985 flood are projected to survive at most a few centuries. In contrast, slackwater sediments inferred to be ≥400,000 years old are preserved within a cave shielded from significant runoff and biogenic activity.

Analysis of small-scale erosional data and a sequence of late Pleistocene flow reversal, northern New England

A sequence of latest Pleistocene ice-flow reversal, principally based on analysis of small-scale erosional features, has been reconstructed for northernmost New England. Single and crossing striations, together with small-scale stoss and lee or other erosional forms, provided more than 1,200 widely dispersed striation sets along with relative age data. The striations were grouped into grids from which vector-mean data were extracted and in turn five zones delineated, each characterized by similarities in ice flow. A sequence of six flow direction shifts between and within zones (for example, east-south-east flow gives way to north flow) was determined using a transition matrix of 159 striation sets. Nondirectional striation data, till-fabric measurements, and glacial-dispersal studies further complement the striation information. All these data were integrated to produce a sequence of ice flow that began with (interval A) east-southeast flow of the Laurentide ice sheet through Maine. Interval B involved a reversal of flow direction from eastward to northwestward in northern Maine, with development of an ice divide. During interval C, this divide strengthened and migrated southeastward, so that by interval D it occurred nearly 120 km southeast of the Quebec-Maine border. Interval E encompassed a final northward flow from the northern flank of the Boundary Mountains and the start of rapid, large-scale stagnation of the last glacier of northern New England.