The general aim of this study was to gain an insight into the nature of gully erosion at Golden Gate Highlands National Park. In order to achieve this the spatial and temporal characteristics of six gullies were investigated by examining their typological and morphological characteristics, the relationship between their morphometric properties and their increase in extent over a 39 year period (1952-1991). Where possible these findings and observed gully forms were related to initiating factors. Extensive field surveys and measurements were carried out to ascertain the typological and morphological characteristics of each gully. The results of the field measurements were then statistically analyzed using linear regression analysis, principal component analysis and canonical variate analysis. These methods of analysis were used to get an indication of the relationships taht exist between the morphometric properties of the gullies as well as to highlight the similarities and differences that exist between them. These results showed that the morphometric varaibles of the gullies are strongly interrelated. Furthermore they revealed that the six gullies could be divided into three broad groups on the basis of their morphometric and sediment properties. The gullies within two of the three groups were found to be similar not only in terms of the above mentioned but they also occur on same facing slopes of similar gradients and appear to have been initiated by similar processes. Differences occurring within and between the gully groups were attributed to varying combinations of initiating factors. Aerial photographs from 1952 and 1984 were used together with surverys to map the extent and development of five of the six gullies - teh remainign gully was only initiated in 1988. The 1952 and 1984 photographs were selected as they represented the earleist and most recent photographs to be taken of the area. The maps show the gullies to have experienced a greater amount of growth during the 1984 - 1991 period than during the 1952 - 1984 period. This finding was attributed to the sporadic nature of gully growth. The spatial location of the gullies in relation to one another appears to have had little influence on their typological and morphological characteristics. However, their spatial location within the landscape has undoubtedly influenced these properties. In general the research described has shown that the spatial and temporal differences of the gullies occurring in the park are the result of various combinations of endogenous and exogenous factors that governed the initiation and development of each gully.

This study aims at uncovering the formation mechanism of the recent bright gully deposits observed on Mars in order to assess the viability of liquid water involvement. I use a high resolution topography model as input into a kinematic model to assess whether or not a dry granular flow could form the bright gully deposits seen in Hale Crater. I investigate a dry mechanism due to the difficulty of producing water on the martian surface under present-day pressure and temperature conditions. I examine a range of particle sizes, flow thicknesses, and upslope initiation points to examine how these parameters affect the run-out distances of flows. The results show that multiple combinations of parameters could produce flows that travel to within the observed deposits' boundaries. The results suggest that the recent bright gully deposits are not evidence of recent liquid water on the surface of Mars.

Geologically young gullies have been proposed to be evidence of recent liquid water on Mars. This dissertation details work I have done to address issues surrounding the Martian gullies and recent water on Mars. In order to determine the elevations at which gullies occur, I created a set of Interactive Data Language programs and Unix C-shell scripts to coregister Mars Orbiter Laser Altimeter topography with high resolution Mars images. My scripts represent the first public method that does this. Recently, the Mars Orbiter Camera detected changes in the form of new bright deposits in two gullies. The High Resolution Imaging Science Experiment (HiRISE) camera detected more gullies with bright deposits. I used my scripts to identify some of the best candidates for liquid water formation based on their shallow average slopes. A Digital Elevation Model (DEM) was produced using HiRISE stereo images of my selected candidates in Hale Crater. I model two gullies with bright slope deposits in Hale Crater and find that both water-rich and sediment-rich flows could reproduce the bright deposits’ locations and morphologies. Since liquid water is rarely stable on Mars today, I suggest that dry flows formed the bright deposits. The channel gradient where flows deposit, the apex slope, can tell us whether a flow was likely dry and non-fluidized (slopes ~21°) or fluidized (shallower slopes). I measured the apex slope of 75 gullies located in five HiRISE DEMs. I find that 72% of the gullies studied were likely emplaced by a fluidized flow. I also find that modified gullies are more likely to have a fluidized emplacement than relatively fresh gullies. My results suggest that there is no evidence requiring water-rich flows in gullies today. Understanding the concept of water on Mars is crucial to understanding NASA’s Mars Exploration Strategy, “Follow the Water.” I undertook a study investigating alternative conceptions about water on Mars held by middle school science teachers to understand what they hear when scientists say “water on Mars.” All study participants had alternative conceptions about water on Mars. I suggest focus topics for space science education programs.

Analysis of impact craters and their ejecta addresses someunanswered questions about the lunar surface. First I estimatethe regolith depth on the south farside of the Moon to be about40 m, which is significantly deeper than the nearside regolith,estimated to be 3-16 m. This result is obtained by studyinghundred meter diameter flat floored craters, using the method ofQuaide and Oberbeck (J. Geophys. Res., 1968, 73, 5247-5270). This measurement has implications for the formation of the lunarregolith, and for interpretation of samples returned in thefuture by astronauts or automated sample return missions.Next, I report the discovery of a method that distinguishesbetween primary and distant secondary craters in high resolutionplanetary images. For a given crater size, the largest bouldersof secondary craters are significantly larger than those ofprimary craters. The ability to identify distant secondarycraters will help constrain primary production rates of smallcraters and improve surface age determination of small areasbased on small crater counts.Third, I characterize the distributions of boulders ejected from18 lunar impact craters. I find that in large craters, thelargest boulders are preferentially ejected at low velocities(closer to the crater), whereas the largest boulders from smallcraters are ejected over a wider range of ejection velocities. Also, for a given crater size, deeper regolith reduces themaximum ejection velocity attained by a boulder ejected from acrater. I show that this is a logical result of the streamlinesof excavation in an impact when there are no coherent boulders inthe regolith. Cumulative plots of the boulders have slopessteeper than -2, as do secondary craters. This result isexpected because ejecta fragments produce secondary craters.Finally, I describe the morphology of some lunar crater walllandslides that strongly resemble martian gullies, despite thelack of geologically active water on the Moon today or in thepast. The lunar features indicate that alcove-channel-apronmorphology, attributed on Mars to seepage of liquid water, canalso form via a dry landslide mechanism. Therefore alcove-channel-apron morphology is not diagnostic of water carvedgullies.

No description available.

Master of Science / Department of Agronomy / Nathan O. Nelson / Phosphorus (P) is an essential nutrient in crop production, but P inputs to surface waters have resulted in impairments such as eutrophication and algae blooms. Non-point sources such as agricultural fields are a main contributor of P. Kansas, being a high agricultural dependent state, has frequent fresh water body impairments. Multiple erosion and transport processes contribute to P loss. While P loss from sheet and rill erosion has been studied extensively, P loss from ephemeral gully erosion is largely unknown. The objective of this study is to understand the effects ephemeral gullies have on the transport and transformation of P. Three fields in McPherson County with well-defined ephemeral gullies were studied. Soil samples were taken in field locations that are effected by ephemeral gullies at the 0 to 2, 2 to 5, 5 to 15, and 15 to 30 cm depths. Samples were analyzed for total P, anion exchange phosphorus (AEP) (labile P), ammonium-oxalate extractable Fe, Al, and P (Fe[subscript]ox, Al[subscript]ox, P[subscript]ox), Mehlich 3 extractable Fe, Al, Ca, and P (Fe[subscript]M3, Al[subscript]M3, Ca[subscript]M3, P[subscript]M3), equilibrium phosphorus concentration at zero net sorption (EPC[subscript]0), 1:1 soil to water pH, and texture. Soil testing showed that P quantities tend to be much higher in surface soils eroded by sheet and rill erosion and lower in subsoil soil that is eroded by ephemeral gullies. The quantity of sorptive elements such as Fe and Al, were not significantly different throughout the tested area except in areas of changing soil texture. EPC[subscript]0 testing showed it was likely that P desorbs from the surface erosion of sheet and rill and is adsorbing onto the subsoil eroded from ephemeral gullies. Sediment eroded by ephemeral gullies has a P buffering capacity greater than the sediment eroded by sheet and rill, and a small quantity of ephemeral gully subsoil will have a large effect on the dissolved P concentration of runoff. Sediment, total P loss and expected dissolved P in runoff was surveyed and modeled for two of the fields. Ephemeral gullies contributed to a majority of sediment and total P loss. The addition of ephemeral gully sediment to the erosional mix of sheet and rill sediment caused the dissolved P concentration to decrease from 0.0204 to 0.0034 mg L[superscript]-1 in one field and from 0.0136 to 0.0126 mg L[superscript]-1 in another. The results of this study show that best management practices (BMPs) such as grass waterways could cause the losses of total P to decrease as much as 2 to 12 times in fields with ephemeral gullies. However, reducing ephemeral gully erosion will likely increase dissolved P concentrations up to 600% more in runoff. Therefore, BMPs need to be combined to fully control P loss from agricultural fields.

The Eel River watershed has a high concentration of slow-moving landslides, or earthflows, due to argillaceous mélange bedrock and high tectonic uplift. Earthflows within this area are highly dissected by ephemeral channels, or gullies. Despite the pervasiveness of gullying in this area, the role of fluvial systems in relation to earthflows and varying uplift is poorly understood. To understand the role of earthflows and tectonics in dictating channel processes, we investigate channels in areas of differential uplift and mass failure activity. Channel networks are connected and continuous in catchments without earthflows, and disconnected and prone to bank failure on earthflow surfaces. Gully profiles are influenced BY earthflow undulations, which attenuate with fluvial incision after earthflows cease activity. We find notable differences in fluvial dissection between areas of high and low landslide activity. We find that mass wasting and local bedrock have a strong influence on formation and organization of channels.

The Antarctic continental margin contains a diverse range of continental slope morphologies, including iceberg keel marks, gullies, channels, mass-wasting features (slides, slumps), ridges, furrows, mounds and trough mouth fans. These features vary significantly in morphology, with bedforms varying in size (width, amplitude and length), shelf incision, sinuosity, branching order, spatial density and cross-sectional shape. The processes which form these features and the environmental controls influencing their morphology are not well documented or well constrained. Understanding the processes operating on the Antarctic continental margin is essential for interpreting seafloor erosion patterns, continental margin evolution, slope instability and sediment core records from the continental slope and rise. Through quantitative analysis of multibeam bathymetric data along >2670 km of the outer shelf and upper-slope of high latitude continental margins, five distinct Antarctic gully types are identified. Gully morphology was found to vary with local slope character (slope geometry, gradient), regional factors (location of cross-shelf troughs, trough mouth fans and drainage basin size), sediment yield and ice-sheet history. Most gullies are likely formed by: (1) flows generated as a result of the release of subglacial meltwater from beneath an ice-sheet grounded to the shelf edge during glacial maxima; (2) turbidity currents initiated by intense iceberg scouring; or (3) small-scale mass-wasting. Erosion by cascading dense water overflow does not form the deeply incised and V-shaped gullies that occur over much of the Antarctic continental margin. A comparison of some Arctic and Antarctic gully morphologies shows that the Antarctic gullies have much deeper mean incision depths and greater shelf-incisions, suggesting that they either formed over significantly longer periods, or by a greater release of meltwater in the areas with greater gully incision depths. The first morphological analysis of the southern Weddell Sea outer shelf and upper slope is presented. Two large and relatively recent submarine slides occur on the Crary Fan, the first Quaternary slides to be documented on an Antarctic trough mouth fan. These slides provide evidence for recent large-scale mass-wasting events on the Antarctic continental margin. The interpretation of bedforms on the outer shelf of the southeastern Weddell Sea provide insight into the timing and extent of past ice and points to grounded ice near to the shelf edge during the Late Quaternary.

No description available.

Doctor of Philosophy / Department of Biological & Agricultural Engineering / Kyle Douglas-Mankin / Soil erosion is one of the most important of today’s global environmental problems. Over the past few decades, soil conservation practices were implemented to reduce soil erosion in the United States. However, excessive sediment still remains among the most prevalent water quality problems. Agricultural fields and in particular ephemeral gullies (EGs) are considered to be a major contributor of sediment. The overall goal of this study was to improve modeling utility to identify and quantify sources of sediment. Specific objectives were: (1) to develop and demonstrate a method of field-scale targeting using Soil and Water Assessment Tool (SWAT) and to use this method as a targeted, flexible approach to pay explicitly for sediment-yield reductions; (2) to evaluate topographic index models (Slope Area [SA], Compound Topographic Index [CTI], Slope Area Power [SAP] and Wetness Topographic Index [WTI]) and a physical-based model (Overland Flow Turbulent [OFT]) in predicting spatial EG location and lengths. Black Kettle Creek watershed was the focus of an innovative project to pay for modeled field sediment reductions. An Arc-Geographical Information System (GIS) tool bar was developed that post processed SWAT hydrologic response unit output to field boundaries and prepared maps of high-priority fields by sediment, total nitrogen, and total phosphorus and was demonstrated to be useful for field-scale targeting. Calibrated SWAT model was used to establish baseline sediment yields. Various Best Management Practices (BMPs) were simulated and payments to implement each BMP for a given field were calculated. This study helped to guide determination of appropriate farmer support payments and quantified the important influence of BMP type and site-specific conditions for use in targeting conservation practice funding to achieve maximum soil-loss reductions per dollar spent. Extreme care should be used in selecting the source of spatial model input data when using SWAT for field-level targeting. Automated geospatial models were developed in a GIS environment to spatially locate and derive length of EGs using topographic index and physical based models. EG predictions were better for the SA model among the four topographic index models tested. Individual calibration of topographic index model threshold for each application site was needed. An OFT model (physical based model), which utilized topography, precipitation, soil, landuse/landcover and SWAT-based runoff estimates, did not need individual site calibration, and may have broader applicability than empirical based models.