Understanding the history of ice on Mars provides important insight into Martian geologic and climatic history. A model capable of ice reconstruction that requires few input parameters, and a detailed analyses of landforms in an area with hypothesized glacial modification, Argyre Planitia, provide further understanding of Martian ice.A threshold-sliding model was developed to model perfectly-plastic deformation of ice that is applicable to ice bodies that deform when a threshold basal shear stress is exceeded. The model requires three inputs describing bed topography, ice margins, and a function defining the threshold basal shear stress. The model was tested by reconstructing the Greenland ice sheet and then used to reconstruct ice draping impact craters on the margins of the Martian South Polar Layered Deposits using a constant basal shear stress of ~0.6 bars for the majority of Martian examples. This result is ~1/3 the value calculated for the Greenland ice sheet. Reasons for the lower Martian basal shear stress are unclear but could involve the strain-weakening behavior of ice. The threshold-sliding model can be used for ice reconstruction and forward modeling of erosion and deposition to provide further insight into the history of ice on Mars.To test the glacial hypothesis in the Argyre region, landforms are examined using images from the High Resolution Imaging Science Experiment (HiRISE) camera and other Martian datasets. Linear grooves and streamlined hills are consistent with glacial erosion. Deep semi-circular embayments in mountains resemble cirques. U-shaped valleys have stepped longitudinal profiles and tributary valleys have hanging valley morphology similar to terrestrial glacial valleys. Boulders blanketing a valley floor resemble ground moraine. Sinuous ridges cross topography, have layers, occur in troughs, and have variations in height that appear related to the surrounding surface slope; these are characteristics consistent with terrestrial eskers. At least portions of Argyre appear to be modified by ice accumulation, flow, erosion, stagnation and ablation. The type and amount of bedrock erosion and presence of possible eskers suggests the ice was, at times, wet-based.

This study investigates channel bed scour and fill as a result of individual flood events in a gravel-bed channel. Given the complexity of interactions between hydraulic force, the texture and arrangement of bed material, and input of sediment to a particular point of the channel bed, study objectives were pursued with the view that bed material movement is a stochastic phenomenon. A two-year field program was conducted in Carnation Creek, a small gravel-bed stream draining 11 km2 on the west coast of Vancouver Island, British Columbia. In the 900 m study reach, an array of measurement techniques, including scour indicators, magnetically-tagged stones, and conventional survey, yielded information about the fluctuations of the channel bed elevation and movement of scoured material for individual flooding periods. Frequency distributions of scour and fill depths associated with individual flooding periods are adequately modeled by negative exponential functions over the range of flood peak magnitudes observed in Carnation Creek. Analysis of scour depths measured in streams on the Queen Charlotte Islands demonstrates the applicability of the exponential model to flooding periods and flood seasons. Further, exploratory analysis suggests that a regional scour depth model is possible. Power functions relating mean depths of scour and fill to flood peak discharge show that depth increases with an increase in peak magnitude. Observed maximum scour depths in flooding periods are linked, in general, to streambed conditions influenced by antecedent flow conditions. These patterns in scour and fill exist within an overall pattern of increasing variability in depths of scour and fill as peak discharge increases. Evaluation of a heuristic model for mean travel distance as a function of particle size proposed by Church and Hassan (1992) provides convincing evidence for its general merit. Mean travel distance decreases inversely with particle size as size increases beyond the median diameter of subsurface sediment. This trend is consistent in both individual flooding periods as well as flood seasons. The majority of material finer than the median diameter of surface sediment is supplied from subsurface material, which influences the travel distances of these finer fractions because of burial. Computation of volumetric transport rates of bed material, based on the active scour depth and width of the channel bed, the virtual velocity of particle movement, and sediment porosity, suggests the potential for building scale correlations with streamflow, which have usually been defined by bedload sampling during floods. Error analysis indicates that determination of active width contributes most significantly to the imprecision of transport rate estimates. Results underscore the stochastic nature of sediment transport in gravel-bed channels.

Until very recently the south-western part of the Eastern Townships had not received a great deal of attention from geomorphologists; indeed in the Eastern Townships as a whole the work has been essentially of a reconnaissance nature. However, lying as it does at the junction of the Appalachian ridges to the south and the St. Lawrence Lowlands to the north, one might expect it to be interesting from two points of view: firstly in having morphological features common to both areas and secondly in offering the possibility of a comparison between their sequences of development. In recent years the attention has been focussed on two particular topics which reflect increasing awareness of the significance of the area as a field of geomorphological research: the development of pre-glacial topography (Sangree, 1953; Bird, 1961) and studies of glacial geomorphology (Dresser and Denis, 1944; Sangree, 1953; Cooke, 1957). [...]

Fluctuations of sea level in the recent past are well documented in the landscapes of northern Canada by the existence of raised strandlines with marine shells and emerged off-shore deposits. However details of these fluctuations in many areas remain to be resolved and their relationship to glaciation and deglaciation needs to be determined. [...]

The Waipara – Kowai groundwater allocation zones (referred to as zones) are located 50 kilometers north of Christchurch. Land use in the Waipara zone has evolved from dry land farming towards horticultural and irrigated pastoral farming, and as such the demand for groundwater resources has increased significantly. Recent 14C age dating has shown that deep wells tap >1000 years old water, raising concerns about possible resource mining. The Kowai groundwater allocation zone has had minimal regional hydrogeological investigations and previously little is known about the groundwater resources here. The Waipara – Kowai groundwater allocation zones are located near obliquely convergent plate margin and the Porters Pass Fault System. Recent (early Quaternary) deformation has been noted by workers along margins and associated with emerging structures within basins. These emerging faults and folds within the basin are acting as hydrological barriers, hindering the passage of groundwater within the basin. A geomorphic map was constructed for this study based on existing soils maps, limited field soil surveys and morphometric analysis. Nine geomorphic surfaces are described, with inferred ages of modern to >73 ka. The geomorphic investigation revealed that the Kowai groundwater allocation zone surface is stepped, with increasing thickness of loess up gradient on the downlands. Near the coast there is intercalated terrestrial and marine sediments, to the west overlying the Kowai Formation are small alluvial fans. In the Waipara Basin the Waipara fan dominates the central portion of the basin, with smaller fluvial and alluvial fans building out from the margins. Groundwater recharge was investigated using chemical, isotopic, water level observations and a simple water balance. It was found that in the Kowai zone the major recharge sources were the rainfall, losses from the rivers and streams. The southern region of the Waipara zone is recharged by rainfall with small contributions from the Kowai River (North Branch). In the South region of the Waipara Basin groundwater recharge is derived from rainfall and losses from streams. The groundwater systems are conceptualized as being topographically driven, with slope – basin floors interactions being an important source of groundwater recharge.

<p> Marine Protected Areas (MPAs) are successful place-based management tools in protecting Essential Fish Habitat (EFH) from commercial and recreational fishing pressures. In the southeast Atlantic, the morphometric environment of the seafloor has been found to be a control on Essential Fish Habitat (EFH) (Sedberry and Van Dolah 1984). To this end, modern methods of acoustic data acquisition and morphometric analysis of the seascape are promising oceanographic techniques for identifying and delineating EFH. In July, 2013, the NOAA Ship Pisces collected bathymetric, backscatter and water column data for potential habitat sites along the U.S. Southeast Atlantic continental shelf. A total of 205 km² of seafloor were mapped between Mayport, FL and Wilmington, NC, using the SIMRAD ME70 multibeam echosounder system. In addition, a total of <i>n</i> = 7410 fish presences were recorded within the water column, using the SIMRAD EK 60 split-beam echosounder system. These data were processed in CARIS HIPS, QPS Fledermaus, MATLAB and Echoview. This study provides a morphometric characterization and quantitative assessment of fish present within each survey site and identifies features of the bathymetry that help explain the presence of demersal fish. A total of 106 unique maps were created, illustrating seafloor morphometrics and fish distributions across the seascape. In ArcGIS, 14 morphometrics were generated as candidate explanatory variables for fish abundances in small (5-12 cm), medium (12-29 cm) and large (>29 cm) size classes. We explored fish-seascape interactions at two spatial scales in the GIS using a site-wide and 50 x 50 m grid scale. At the site- wide scale, <i>X&macr;</i> Slope (R² = 0.97), <i> X&macr;</i> Slope of Slope (R² = 0.90) and &sigma; Depth (R² = 0.87) provided the strongest explanatory power in a bivariate analysis and may be used to help identify EFH at a coarse scale. At a 50 x 50 m grid scale, <i>X&macr;</i> Slope, <i>X&macr;</i> Slope of Slope and <i>X&macr;</i> Backscatter emerged as the strongest contributing variables, when combined in a multivariate analysis. Overall, multivariate model R² values were low and not predictive, but allow for the identification of variables contributing to the characterization of fish-seascape interactions at a finer scale.</p>

<p> ¹⁰Be_met, or cosmogenic beryllium, has a long half-life of 1.4 million years and quick adsorption on soil particles, which may make it ideal for dating soil erosion in historical context. However, there are questions on about the fundamental assumptions of the retentivity of ¹⁰Be_met. This manuscript explores these assumptions and the context of nutrient cycling in a natural forest setting. </p><p> To see if ¹⁰Be_met was being cycled through the trees, and at what rate, we looked at the[¹⁰Be_met] in the soil, 4 species of trees, and their leaves. The isotopic ratio¹⁰Be/⁹Be in all four tree species was comparable to the soil on which they grow, ranging from 6-8 x 10 ^-9. However, there was one exception with hickory (<i>Carya spp.</i>) which strongly bioaccumulate beryllium with an average of 0.38 ppm dry weight in the wood. Abscised hickory leaves have a higher [Be] of 2.0 ppm, over 10 times higher than in the soil. </p><p> Using standard allometric equations relating tree biomass to trunk diameter, and assuming that belowground biomass has the same [Be] as aboveground, we calculate that hickory trees at our site contain approximately 1% of the total ¹⁰Be_met under their canopy and that ~10% of this Be is cycled annually by leaf abscission. It is not clear at this point what fraction of litterfall Be is recycled into the plant, returned to the soil, or carried to groundwater as organic chelates. </p><p> Hickory trees occupy an average of ~10% of the oak-hickory forest area. Assuming that trees are randomly distributed, that litterfall Be is returned to the soil, and maintaining a constant ¹⁰Be_met budget over time for simplicity, then more than half of all ¹⁰Be_met in the forest soil will have passed through a hickory tree over the past 10 ky. Fully 90% of all ¹⁰Be_met will pass through a hickory tree over a period of ~25 ky. It is clear that hickory trees can transport a sizable fraction of the total ¹⁰Be_met in their nutrient cycle, and that they may be responsible for landscape-scale Be mobility.</p>

The main focus of the present study is to identify and integrate the factors affecting the degree of irregularity of five continental divide traces, as expressed by their fractal characteristics measured by the divider method. The factors studied are climate, relief and tectonic environment. The second objective of this study is to determine the relationship between uplift rates and divide trace fractal dimension. Analysis of the results suggests that the degree of irregularity of continental divide traces at fine scale (approximately 10-70 km of resolution) is strongly affected by both climate and tectonics. It is found that control of the factors is generally weaker at coarse scale (above approximately 70 km of resolution). Generic relief should be ranked below both climate and tectonic environment as a factor affecting the complexity of continental divide traces. In terms of the second objective, the fractal dimension at fine scales follows a weakly inverse relationship with uplift. At coarse scale, there is stronger inverse relationship between uplift rate and fractal dimension. / Introduction -- Methodology -- Geomorphic environment -- Evaluation of results -- Significance of control factors -- Conclusion. / Department of Geological Sciences

<p> Two US Forest Service draft monitoring protocols are used to assess the effectiveness of design channels at road-stream crossings by comparing their physical channel dimensions to those in the natural channel. Level II physical monitoring is a time intensive, quantitative and statistically based procedure for assessing effectiveness at selected sites. Level I physical monitoring is a less detailed, rapid procedure limited to a few simple measurements and observations for assessing effectiveness at a large number of sites. Study objectives were to: 1) test and refine the field methods for collecting data by the levels I and II physical monitoring protocols; 2) find a meaningful way to combine the data collected by levels I and II into separate effectiveness evaluations by each protocol; and, 3) evaluate whether the level I protocol can be used as a proxy for the level II protocol. Where the two protocols systematically differ, field data help distinguish why. </p><p> Study results for all objectives (combined) include: improved field methodologies, recommendations for further development, and separate summary rubrics for the levels I and II monitoring protocols. The recommendations are of three categories; channel metrics/data collection, methods of scoring each metric, and sample sizes. Some of most significant of those recommendations are described within the following paragraphs. </p><p> Data collection methods might be improved to save time, increase the accuracy of protocol evaluations, and facilitate agreement between the levels I and II protocol evaluation results. The techniques by which the level I bankfull stage and coarse fraction of the gradation metrics are collected should incorporate level II methods. Instructions for collecting level II coarse fraction of the gradation data should specify measuring all particles within the channel, including particles much larger than the sampling frame. The level I method by which the representative reach is selected should incorporate a basic longitudinal profile survey in which only the most prominent grade controls separating slope segments are captured. Decreasing the allowable gradient difference between the level II design channel and representative reach might also improve accuracy. The method by which the levels I and II protocols compare channel units (or channel unit sequences) between the design and representative reach should be equivalent, as should the rules by which slope segments and channel units are defined. Finally, the channel metrics of low flow width and bed irregularity are inconsistent with the objectives of physical effectiveness monitoring, in that they are aspects of habitat, rather than strong controls on channel form. I suggest they be eliminated from the levels I and II protocols. </p><p> The level II summary rubric scores most metrics statistically by a Wilcoxon Rank-Sum test of medians. For most metrics, the Wilcoxon Rank-Sum test appears to be a reasonable way to compare representative reach and design zone data. For the metrics of bed and bank irregularity, however, a test of distributions (e.g., Kolmogorov-Smirnov) is recommended instead. The coarse fraction of the gradation metric would be more fairly assessed if the modes of the particle size (in phi units) were compared instead of the medians. Doing so would allow the design and representative reach gradients to be slightly different (as does the criteria for selecting a representative reach) without penalizing the metric score. </p><p> The levels I and II summary rubric tools created were used to evaluate twelve AOP road-stream crossing designs. The performance of the levels I and II summary rubrics were then assessed by the evaluation results at those twelve sites. Levels I and II generally seemed to provide effectiveness evaluations which agreed with site observations, data, and photographs. Further, the summary rubrics facilitated concurrent evaluation of the many channel dimensions which together affect the hydraulic conditions experienced by aquatic organisms. In addition, the simple utility of the levels I and II summary rubric tools should encourage effectiveness monitoring and help restoration practitioners learn from their mistakes, ultimately improving aquatic organism passage design methods and results. (Abstract shortened by UMI.)</p>

Previous works have applied the Divider Method to the shapes of drainage divides as measured from maps. This study focuses on the shapes of several drainage divides measured in the field at very fine scale. These divides, chosen for their sharp crests, include portions of the Continental Divide in Colorado and badlands-type divides in Arizona, Wyoming, South Dakota, and Texas. The badlands type divides were delineated using a laser theodolite to collect data at decimeter point spacing, and the Continental Divide segments were delineated using pace and bearing at a constant point spacing of 30 meters. A GIS was used to store and visualize the divide data, and an automated divider analysis was performed for each of the 16 drainage divides.The Richardson plots produced for each of the drainage divide datasets were visually inspected for portions of linearity. Fractal dimensions (D) were calculated using linear regression techniques for each of the linear segments identified in the Richardson plots. Six of the plots exhibited two distinct segments of linearity, nine plots exhibited one segment, and one plot exhibited no segments of linearity. Residual analyses of the trend lines show that about half of the Richardson plot segments used to calculate D exhibit slight curvature. While these segments are not strictly linear, linear models and associated D values may still serve well as approximations to describe degree of divide wandering.Most (20 out of 21) of the dimensions derived from the Richardson plots for the drainage divides fall within the range from 1.01-1.07. The D values calculated for the Continental Divide range from 1.02-1.07. The dimensions calculated for the badlandtype divides were distributed evenly across the range of 1.01-1.06, with a single exceptional D value at 1.12. Only four of the divide D values fall within a range of 1.06–1.12, the range for D established for drainage divides in published map-based studies, despite the apparent dominance of erosion processes on the measured divides. / Department of Geology