Late Holocene Aggradational Processes and Rates for Three Alluvial Fans, Cascade Foothills, Washington

Aggradation histories going back to the mid Holocene were compiled by subsurface investigation for three alluvial fans in the Cascade foothills, northwest Washington. Sygitowicz, Radonski, and Hardscrabble Creeks originate on the east slope of Stewart Mountain in steep, wooded watersheds (0.36 to 5.5 km2) and drain to the South Fork Nooksack River valley where they have built small (0.28 to 0.61 km2) post-Pleistocene alluvial fans. Ten trenches, excavated to a depth of 3 to 5 meters on the three fans, exposed well-preserved strata and paleosols. The processes of strata deposition were identified by correlation with the known mode of modern fan deposits. Gravelly debris flow and hyperconcentrated flow processes (totaling 39 percent and 37 percent of average vertical exposures, respectively) are responsible for most of the ancient fan aggradation. Woody debris flows, common in the twentieth century, make up five percent and stream deposits comprised twelve percent of the total vertical exposures measured. Nineteen radiocarbon ages were obtained from six of the ten trenches. The results indicate that all three fans have been aggrading from the mid Holocene (6,000 years B.P.) to the present, and the rates of fan aggradation increase for five of six trenches in this time period. The increase in fan aggradation corresponds to an increase in the frequency of debris flow despite the overall thinning of the debris flow deposits with time. The average recurrence interval is 868 years for ancient debris flows to be deposited at a given point on a fan surface. A change to a cooler, moister climate in the late Holocene, as indicated by climate models and pollen studies from this region, is likely to have contributed to the increased sedimentation seen in the fan strata during this time

A Geoarcheological Survey of the Proposed Plainview Hike and Bike Trail, Hale County, Texas

In March of 2005, the Texas Department of Transportation issued work authorization #575-01-SA005 to the Center for Archaeological Research (CAR) at the University of Texas at San Antonio to conduct a survey of areas affected by proposed improvements to the Plainview hike and bike trail in southern Plainview, Hale County, Texas. The survey was conduced under Texas Antiquities Permit #3707 between March 31 and April 7, 2005. Steve Tomka and Raymond Mauldin served as Principal Investigators. Trail construction included 2.0 miles of additional construction and 1.3 miles of improvements to existing trails. The Right-of-Way is 50 feet and extends from one to three feet below ground surface. Archeological services included a pedestrian survey, excavation of fifty-five auger tests placed no more than 100 m apart, and twenty-one Gradall trenches. Two of these trenches exposed the stratigraphy of Running Water Draw near the Plainview Site, 41HA1. Bulk samples were collected for OSL dating, diatoms analysis, and lithologic analysis for further examination of the age and stratigraphic context of the Plainview Site, which is a State Archeological Landmark, a National Landmark, and a National Register of Historic Places property. Site 41HA12 was re-examined with 10 mechanical auger tests and 1 trench, which found only recent alluvial and cultural deposition. No additional archeological sites were recorded. This report includes descriptions of the fieldwork, results of the special analyses performed on bulk sediment samples collected, and a discussion of the geomorphology of Running Water Draw with specific focus on the results from trenches excavated near the Plainview Site. The single artifact and all documents and photographs generated from this project are curated at the Center for Archaeological Research at The University of Texas at San Antonio

Documenting the Earthquake History of the Thousand Springs Fault in Summer Lake Basin, Oregon, USA

Defining seismic hazards in low-strain-rate regions such as the northwestern Basin and Range can be difficult due to the infrequency of earthquakes. Revealing the earthquake records of low-strain-rate regions can refine our understanding of the variability of earthquake sizes and recurrence intervals, however, which can ultimately improve hazard analysis. Four active normal faults form the Summer Lake basin, in the northwestern Basin and Range: The Thousand Springs (TSF), Ana River (ARF), Slide Mountain, and Winter Ridge faults. Other than the TSF, the faults in the Summer Lake basin have documented histories that include surface-rupturing (\u3eM6) earthquakes. Scarps along the TSF were only recently mapped and its earthquake history has not been previously documented. The TSF cuts through an area with relatively low sedimentation rates and numerous tephras from the past ~250,000 years and thus earthquakes on this fault are preserved and dateable through trenching. We dug two trenches across the TSF in 2019, exposing multiple episodes of offset bracketed by deep to shallow-water lake sediments, a sand dune, and tephras which were identified based on correlations of their physical characteristics, stratigraphic sequence, glass chemistry, and radiocarbon dates from the lake sediments: Tephra 2 (Ice Quarry tephra), Pumice Castle tephra, Mount St Helens Cy tephra, Wono tephra, Trego Hot Springs tephra, Mount St Helens Mp, and a black tephra. These tephras, and a sand dune most likely containing reworked Mazama ash and lacustrine sediments, are offset by a fault zone that spans a minimum of four meters with at least five fault strands. The only unit that was able to be correlated across the fault zone, MSH Cy tephra, had a total offset amount of 2.4 m. The next youngest tephra, Wono, is offset by 2.0 m and THS is offset by 1.8 m, which were both determined by extrapolating missing sections. Based on offset of individual tephras and the comparison between the two trenches, we have identified at least five surface-rupturing earthquakes. The events in chronological order are as follows: The oldest event (event 5) occurred 54.1 – 71 ka, event 4 occurred 30.5 – 45.6 ka, event 3 occurred 24.8 – 29.1 ka, event 2, which was a folding event at our sites, occurred 7.6 – 12.7 ka, and the most recent event (event 1) occurred after 7.6 ka. These results suggest that the TSF is just as active as the nearby Ana River Fault, which has had at least 8 earthquakes in the past ~80 ka compared to the TSF’s 5 earthquakes. Comparing the TSF’s activity to lake level changes in the basin during the Quaternary suggests that the crust could be responding to the changes of the lake level, causing variability in the earthquake recurrence intervals. These insights are applicable to the forecasting of earthquakes in the northwestern Basin and Range and other low-strainrate regions

A geomorphic and hydraulic investigation in the context of floodplain revegetation; based on a soil bioengineering application on the Mattole River, Petrolia, California, USA

As fluvial, riparian and floodplain ecosystem functions are recognised for their role supporting fisheries and ecological values, recovery of streamside vegetation is increasingly important in river 'restoration'. Fluvial geomorphology and hydraulic engineering do not yet account well for the role of vegetation in fluvial processes. This research addresses the need for greater understanding of woody riparian vegetation influences on the hydraulics of overbank flow and floodplains sedimentation. Original hypotheses, research design, and data collection were generated by the student to address this gap in knowledge. A soil bioengineering design was constructed on the Mattole River, California, to revegetate the floodplain for better fish rearing habitat. Field data collection was carried out on this unregulated river for two flood events. The sediment samples resulting from a 1.25-year flow permitted the field testing of an hydraulic flume model of vegetation trapping efficiency. From velocity profiles measured during a I5-year storm event, the bed shear stress reduction caused by the vegetation was computed to be approximately 70-90%. A survey conducted in the UK and internationally evaluated from literature, hydraulic researchers and practitioners of river revegetation, the extent of and gaps in knowledge with regard to river bank stabilisation using live vegetation. A flume flow visualisation study simulated the hydraulic behaviour observed on the Mattole floodplain, which enabled characterisation of flow behaviour through a porous filter medium. Results of this research indicate that flexible woody stems have a profound 'calming' effect on overbank flow. These effects are propagated in the downstream direction at least five and as much as ten times the width of the baffle, much further than previously indicated. This research suggests that flexible vegetation is extremely effective in trapping fine (clay) sediments, contrary to general understanding and of importance for fish habitat. For hydraulic reasons, constructed zones of shrubs, such as the siltation baffle, could be spaced further apart than current design practise indicates

A multibeam bathymetric survey of Bay of Islands, Newfoundland: new evidence of late-glacial and Holocene geological processes

Multibeam bathymetric imagery of Ray of Islands, Newfoundland, is interpreted within the context of late-glacial and post-glacial processes- West of Humber Arm, the fiord floor is irregular and deep. Humber Arm has steep sidewalls and a flat floor. It contains glaciomarine mud. capped by a layer of red mud probably derived from the Deer Lake Basin, which was connected to the ocean ca. 12.2 ka. In the early postglacial period, sediments on the fiord sidewalls slid into deep water, forming erosional channels. Depositional lobes, stacked in many areas, overlie glaciomarine sediments in deep water. The glaciomarine and submarine slide sediments are overlain by postglacial mud that is imprinted by elongate, ovoid, and circular fluid-escape trenches, and sedimentary furrows. The natural morphology of the fiord has been modified by anthropogenic activity at Comer Brook. Effects include an apron of bark offshore from the paper mill, dredge spoil, and a sunken vessel at the mouth of Humber River. Large submarine slides, probably triggered by wharf construction at Seal Head, formed deep channels on the fiord sidewalls and overlapping depositional lobes on the fiord floor. They are morphologically similar to the lateglacial slide failures in the fund. RÉSUMÉ Les images bathymétriques multifaisceaux de Bay of Islands, Terre-Neuve, sont interprétées dans le contexte des processus tardiglaciaires et post-glaciaires. À I'ouest de Humber Arm. Ie fond du l’jord est irrégulier et profond. Humber Arm est doté de parois abruptes et d'un fond plat. Il renferme de la boue glaciomarine recouverte d'une couche de boue rouge provenant probablemenl du bassin du lac Deer, qui était relié à l'océan il y a environ 12.2 millies d'années avant nos jours. Au début de la période post-glaciaire, Ies sediments sur Ies parois du l’jord ont glissé a l’intérieur de I'eau profonde en formant des chenaux d'érosion. Des lobes sédimentaires s'empilant en de nombreux endroits recouvrent les sédiments glaciomarins en eaux profondes. Les sédiments de glissement glaciomarins et sous-marins sont recouverts d'une boue post-glaciaire marquée de tranchées allongées, ovoides et circulaires d'évacuation des liquides et de silions sédimentaires. L'activité anthropique a modi fié la morphologic naturelle du l’jord a Corner Brook. Les effets de cette activité comprennent un tablier d'écorce au large de la papeterie, des matériaux de dragage et un navire ayant coulé à I'embouchure dc la riviére Humber. D'importants éboulements sous-marins, probablement causés par la construction du quai de Seal Head, ont formé des chenaux profonds dans les parois du l’jord et des lobes sédimentaires qui se superposcnt sur Ic fond du l’jord Ceux-ci sont morphologiquemcnt analogues aux fractures de glissement tardiglaciaires dans le l’jord. Traduit par la rédactio

Bridge Deck Runoff: Water Quality Analysis and BMP Effectiveness

INE/AUTC 10.0

Geoarcheological Investigations of Wetland Cell D Within the Dallas Floodway Extension Project Area, Dallas, Texas

The Dallas Floodway Extension project is designed to provide flood damage reduction and environmental restoration within the Trinity River flood plain between the Corinth Street Viaduct and Loop 12. The U.S. Army Corps of Engineers, Fort Worth District, contracted with Geo-Marine, Inc., to conduct an archeological assessment of the proposed Wetland Cell D. The archeological assessment was to identify any potential archeological sites that may be eligible for inclusion in the National Register of Historic Places and to provide an assessment of the potential for buried landforms in the project area that may have intact archeological resources present. The geoarcheological investigations, involving the excavation of 10 backhoe trenches and the review of previous data collected within the Upper Trinity River drainage, revealed that the flood plain sediments of the Trinity River are quite variable, both horizontally and vertically. The data collected during the current investigations suggest that Cell D is located along or near the axis of a recent Trinity River meander belt that has cut deeply into the preexisting Quaternary sediments. This channel cut was then rapidly filled with fine-grained deposits possibly derived from the surrounding uplands and other areas upstream. In addition, the trenching revealed that the upper portions of the sediments within Cell D have been disturbed during the recent historic period, presumably by the construction of the Interstate 45 bridge and the activities of the nearby Dallas Central Wastewater Treatment Plant

Neotectonics and Paleoseismicity of a Major Junction Between Two Strands of the Awatere Fault, South Island, New Zealand

In northeastern South Island, New Zealand, obliquely-convergent relative motion between the Pacific and Australian plates is accommodated by slip across active dextral-oblique faults in the Marlborough fault system. The Awatere Fault is one of four principal active strike-slip faults within this plate boundary zone, and includes two sections (the eastern and Molesworth sections) that have different strikes and that join across a complex fault junction in the upper Awatere Valley. Detailed mapping of the fault traces and measurement of 97 geomorphic displacements along the Awatere Fault in the vicinity of the fault junction show that the eastern and Molesworth sections of the fault intersect one another at a low angle (10-15º), at the eastern end of an internally faulted, elongate, ~15 km long and up to 3 km wide fault wedge or sliver. The region between the fault sections is split by a series of discontinuous, en-echelon scarps that are oriented from ~10º to 20-30º clockwise from the principal fault sections. Based on other observations of discontinuities in strike-slip earthquake ruptures around the globe, this low-angle intersection geometry suggests that the junction between these fault sections may not act as a significant barrier to earthquake rupture propagation. This interpretation of the mechanical significance of the fault junction to earthquake ruptures is counter to previous suggestions, but is supported by new paleoseismic data from four paleoseismic trenches excavated on each side of the junction. In a new paleoseismic trench on the Molesworth section at Saxton River, 18 km to the west of the junction, up to ten surface-rupturing events in the past ~15 ka are recognised from 12 radiocarbon ages and 1 optically stimulated luminescence age. In two new trenches on the eastern section near to Upcot Saddle, 12 km northeast of the fault junction, five events took place in the past 5.5 ka, based on 21 radiocarbon ages. This chronology from Upcot Saddle is combined with data from two previous trenches located ~55 km to the northeast at Lake Jasper, to infer nine events on the eastern section since 8330-8610 cal. years B.P. These well-dated events on the eastern section are compared to those on the Molesworth section to the west of the fault junction. At 95% confidence, five events on both sections have occurred with statistical contemporaneity since ~6 ka B.P. These five events may have ruptured both the eastern and Molesworth sections simultaneously, in accordance with the interpretation that the fault section junction does not arrest rupture propagation. Alternatively, these events may have been separate earthquakes that occurred within the statistical resolution provided by radiocarbon dating. The most recent event to rupture the eastern section was the Mw ~7.5 1848 Marlborough earthquake. The coseismic slip distribution and maximum traceable length of this surface rupture are calculated from the magnitude and distribution of small, metre-scale geomorphic displacements attributable to this earthquake. These data suggest this event ruptured >100-110 km of the eastern section, with mean surface displacement of 5.3 ±1.6 m. Based on these parameters, the moment magnitude of this earthquake would be Mw 7.4-7.7. This magnitude estimate is indistinguishable from previous calculations that were based on attenuation of shaking intensity isoseismals that were assigned from contemporary historical accounts of that earthquake. On the basis of similar rupture lengths and coseismic displacements, it is inferred that the penultimate event had a similar moment magnitude to the 1848 earthquake. Horizontal displacement of a flight of 6 fluvial terraces at Saxton River by the Molesworth section of the Awatere Fault is constrained to have occurred at a nearconstant rate of 5.5 ±1.5 mm/a since ~15 ka B.P. These rates are based on two new optically stimulated luminescence ages for the highest terrace treads of 14.5 ±1.5 and 6.69 ±0.74 ka B.P. These rates are indistinguishable from recent strike-slip rate estimates for the eastern section of 5.6 ±1.1 and 6 ±2 mm/a. Comparing the magnitudes and ages of the terrace riser displacements at Saxton River to the timing of paleoearthquakes on the Molesworth section implies a mean per-event displacement of 4.4 ±0.2 m since ~15 ka. The new terrace ages also record two periods of aggradation that post-date the Last Glacial Maximum

Contour Trenching as a Strategy in Watershed Rehabilitation: Application to Nepalese Condition

The disastrous soil erosion problems and the uncontrolled movement of water in Nepal\u27s mountains caused by human and livestock activities call for the identification of simple, cheap, and effective rehabilitation techniques. This report analyzes contour trenching as rehabilitation techniques in the United States and examines the applicability and transferability of the techniques to the Nepalese conditions. The details of contour trench systems as applied by the U. S. Forest Service have been analyzed by reviewing available research papers, handbooks, official records, personal communication, and actual field visits. The results and observations have been delineated for the physical and cultural aspects of the Nepalese watershed system. Contour trench systems in the United States are designed to hold overland runoff resulting from a high~intensity, short duration rainfall events. The idea is to store overland flow on site and allow it to percolate slowly into the soil. Trenches are an interim measure and are no substitute for rehabilitation measures designed to reduce runoff and erosion for a prolonged period of time, Quantitative evaluation of trenching effects are lacking. The findings of the few quantitative studies report the combined effects of trenching, grazing and fire control. There are examples of tremendous success and disastrous failures. Contour trenches are delicate structures. Evaluation by experienced personnel reveals that contour trenching has a definite role in the rehabilitation of impaired watersheds if the plan is carried out systematically and precisely. Contour trenches have questionable benefits in areas where large volume, long duration and possibly high intensity rains occur (such as the monsoon areas). Thus, this control method has its limited role in the overall strategy of rehabilitation planning in Nepal. The primary limitation as seen from the analysis is the huge amount of long duration rainfall and direct runoff produced. However, there is some potential for application of contour trenching in the semi-arid parts of Nepal where frequent floodings are caused by short duration, high intensity rainfall. Watershed rehabilitation techniques developed in U. S. can be applied in Nepal in certain cases. However, site specific research support is essential in designing control structures. Nepal needs to develop research projects to identify and apply alternative rehabilitation techniques which can handle large volume of uncontrolled water over the impaired watershed

Preliminary Cultural Resources Investigations for the Pharr-Reynosa International Bridge, Hidalgo County, Texas

Archeological, archival, and geomorphologic investigations were conducted for the proposed Pharr-Reynosa International Bridge Project in Hidalgo County, Texas, by Prewitt and Associates, Inc. from October 12-27, 1992. The purposes of these investigations were to locate and record any cultural resources within the project area, determine their eligibility for listing on the National Register of Historic Places and designation as State Archeological Landmarks, and to provide an overview of the Holocene geomorphic history of the project area. The geomorphic history of the project area suggests that the Rio Grande has experienced continuous channel aggradation from the end of the Pleistocene to ca. 1000 B.P. Climatic changes and diminishing sediment loads led to channel incision around 1000 B.P., forming a low late Holocene terrace and resulting in increased sinuosity and a decreased channel width-to-depth ratio. The investigations included a stratified sample survey of approximately 162 hectares (400 acres) and the excavation of 16 backhoe trenches and 14 shovel tests. A total of 10 sites, consisting of 10 historic and 2 prehistoric components, were documented. Six standing architectural properties, each consisting of a structure or groups of structures, also were documented. Four of the sites (41HG153, 41HG155, 41HG156, and 41HG158) are considered to be potentially eligible for listing on the National Register of Historic Places and for designation as State Archeological Landmarks. Two of the architectural properties - the Carmichael and Sorenson farmsteads - also may be eligible for listing on the National Register. The four potentially eligible sites consist of four historic and two prehistoric components. The historic components date from the Texas Republic period to the early twentieth century, representing the establishment and development of the EI Capote Ranch community. The two prehistoric components (41HG153 and 41HG158), of which only 41HG153 is potentially eligible, represent Late Prehistoric and unknown prehistoric components, respectively