Anthropogenic disturbances are increasing in arid lands, as are expectations to successfully minimize impacts to natural resources and reclaim sites to publicly acceptable levels. This research explores the effectiveness of reclamation practices on a 60 mile natural gas pipeline constructed in September of 2014 that spans from west of Tucson to the border of Mexico. First, a controlled field experiment was conducted to assess the effects of seeding, grazing, and trampling (vehicular, cattle, and human foot traffic) on the reclaimed pipeline Right-Of-Way (ROW). Vegetation establishment (native plant cover; undesirable plant cover; species richness; herbaceous biomass), soil movement, and plant functional group community development was compared among the treatments. Reclaimed ROW areas left to recover without seeding resulted in similar vegetation cover, species, and community composition as undisturbed desert areas, although the presence of undesirable species was greater. The combined impacts of grazing and trampling resulted in reduced vegetation establishment and increased soil erosion. Second, the impacts of the pipeline construction on ephemeral wash channels were analyzed in terms of channel morphology and riparian vegetation changes. Channel cross section dimensions were measured upstream of the ROW, downstream of the ROW, and within the ROW before and after the 2015 Monsoon season to evaluate impacts on channel morphology and erosion processes. High resolution aerial imagery taken before and after pipeline construction was used to evaluate changes in riparian vegetation cover. Reduced herbaceous vegetation cover downstream of the ROW was detected, which may have been the result of increased channel scour within the ROW and increased sediment deposition downstream of the ROW. This research improves our understanding of and may aid in selection of appropriate reclamation practices.

This study investigates gully erosion on an east Tennessee hillslope in a humid subtropical climate. The study area is deeply gullied in Ultisols (Acrisol, according to the World Reference Base for Soil), with thirty years of undisturbed erosional history with no efforts to correct or halt the erosion. The objectives are (1) to examine how different gully morphologies (channel, sidewall, and interfluve) behave in response to precipitation-driven erosion, and (2) to identify an appropriate temporal scale at which precipitation-driven erosion can be measured to improve soil loss prediction. Precipitation parameters (total accumulation, duration, average intensity, maximum intensity) extracted from data collected at an on-site weather station were statistically correlated with erosion data. Erosion data were collected from erosion pins installed in four gully systems at 78 locations spanning three different morphological settings: interfluves, channels, and sidewalls. Kruskal-Wallis non-parametric tests and Mann-Whitney U-tests indicated that different morphological settings within the gully system responded differently to precipitation (p<0.00). For channels and sidewalls, regression models relating erosion and precipitation parameters retained antecedent precipitation and precipitation accumulation or duration (R2=0.50, p<0.00 for channels, R2=0.28, p<0.00 for sidewalls) but precipitation intensity variables were not retained in the models. For interfluves, less than 20% of variability in erosion data could be explained by precipitation parameters. Precipitation duration and accumulation (including antecedent precipitation accumulation) were more important than precipitation intensity in initiating and propagating erosion in this geomorphic and climatic setting, but other factors including mass wasting and eolian erosion are likely contributors to erosion. High correlation coefficients between aggregate precipitation parameters and erosion indicate that a suitable temporal scale to relate precipitation to soil erosion is the synoptic time-scale. This scale captures natural precipitation cycles and corresponding measurable soil erosion.

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No description available.

No description available.

Forests of the Southeastern United States produce approximately 12% of all the world's wood products and represent 40% of all U.S. timberland, thus emphasizing the importance of Southeast in support of the United States' role as the world's largest timber producer. Producing such quantities of timber requires a substantial areas of forest harvest operations, which have the potential to disturb soils, facilitate erosion and potentially reduce water quality. Harvest sites routinely contain operational features such as skid trails, harvest areas, haul roads, decks/landings and stream crossings, all of which have the potential to influence erosion and sediment deposition in streams. Forestry best management practices (BMPs) were created to minimize the effects of harvesting operations on sedimentation and are implemented at varying levels throughout the Southeastern U.S. We quantified the area of these features on 111 recent harvest sites throughout 11 Southeastern states and three physiographic groupings (Mountains, Piedmont, Coastal Plain). No significant differences were found between the groupings with regard to the percent of area occupied by each operational feature. Decks, haul roads, skid trails, and stream crossings comprised an average of 1.43%, 3.21%, 7.03%, and 0.19% of the harvest operations. Roads, decks, skid trails, and structures were combined into an access feature category. These combined access features occupied 13.0% of harvests in the Mountains, 10.2% in the Piedmont, and 10.4% in the Coastal Plain (10.4%). A companion study was developed to trap sediment delivered to the stream and quantify the sediment delivery ratios (SDRs) on a subset of harvests sites in order to determine the average amount of eroded material that could reach a stream from each specific operational feature following a harvest. Across all groupings, stream crossings had the highest average SDR (34.32%), while skid trails had the second highest SDR (21.04%). Substantial site variability resulted in large SDR differences with few meaningful significant differences, but stream crossings, skid trails, and haul roads had sufficiently high sediment delivery ratios across all groupings to warrant additional BMP focus on these areas. / Master of Science / The Southeastern United States is a major producer of forests and forest products, comprising about 40% of US timberland and 12% of global wood products. Support of this industry requires that over 4 million acres of forests are harvested annually across the southeastern U.S. and improper or under usage of forestry best management practices could result in soil erosion and subsequent transport to streams as sediment. Previous research indicates that different operational and access features found on logging sites have different erosion rates yet little data exists which document the percentages of erosion that is delivered as sediment to streams. Skid trails (trails that forestry equipment use within a harvesting operation) compromised the largest access feature average percent area (second to harvest area), followed by haul roads, then decks (area where equipment is kept and logs are processed and loaded), and finally stream crossings with the smallest average area. Stream crossings, skid trails and haul roads consistently had the highest average sediment delivery ratios for all groupings combined. However, substantial site variability resulted in large sediment delivery ratio differences with few meaningful significant differences.

The erosion process was characterized on two small agricultural watersheds in Piedmont Virginia. Rainfall and runoff were measured for all storms at both watersheds over a two year monitoring period. Although the data base was relatively short, the data covered a wide range of rainfall and runoff conditions. Runoff samples were collected, analyzed, and used to compute loading rates of sediment, nitrate N, ammonium N, TKN, orthophosphate P, and total P on an event basis. Yields from missed storms were estimated from log-log linear least squares regression rating curves. Seasonal and annual totals of loading rates were computed by summing the yields for all storms. Existing estimation techniques were used to calculate rainfall energy, rainfall energy contributing to rainfall, the runoff/rainfall ratio, gross erosion and delivery ratios. USLE C-factors for each field were evaluated for changes in crop and cover conditions. Enrichment ratios for available P, nitrate N, and TKN were estimated on an annual basis. Clay enrichment and particle size distributions of the surface soil and the sediment in runoff from each watershed were also determined. These erosion characteristics were contrasted between the two watersheds whose land management practices differed. A comparison between years was also made on the conservation watershed, where part of the conservation plan was abandoned the second year. The use of conservation practices resulted in smaller estimates of gross erosion, smaller sediment and sediment-bound nutrient yields, and less runoff. / M.S.

Conservation agriculture has many potential benefits for small farmers. This study seeks to estimate the value that farmers in eastern Uganda place on some these benefits. Data from a choice experiment study are analyzed with a mixed logit model to determine farmers' willingness to pay for increases in maize yield, reductions in erosion, and reductions in land preparation labor requirements. It finds that farmers have a statistically significant willingness to pay for increases in yield and reductions in erosion, but not for reductions in planting labor. In addition, farmers in Kapchorwa district value erosion control and labor reductions more and price increases less than in Tororo district, while women care more about price increases than men do. / Master of Science / CCRA-6 (Economic and Impact Analysis)

This research analyzes private and social costs of forest conservation in Yaque del Norte watershed, DR. It calculates private costs as average annual income from farming activities and social costs as the externalities from erosion and CO2 emissions. Social cost estimates are based on the difference in erosion and CO2 between conserved forest and other land use categories. The effect of soil erosion on the wellbeing of people is measured by its effect on reduced space at Tavera dam for water availability to generate electricity and to irrigate agricultural lands downstream. The social cost of increased annual carbon emission from potential land use change is estimated using IPCC default emission factors and social cost of carbon estimates. Private costs are inferred from a nonlinear binary response model that estimates the relative importance of factors affecting forest conservation decisions of households. Results show that payment level, measured through rental value, is not significant for landholders' decisions to sign a PES contract. Annual cropland is the most profitable land use in the area. Other important, but less profitable, land covers are pasture, coffee and managed forest. Cropland also generates the highest cost for society in terms of erosion and CO2 emissions. The comparison of private and social costs shows that only livestock generates a social cost that exceeds average private income. If forest conservation were to be justified based on social benefits, the analysis must include a more comprehensive assessment of what people value from conserved forest in YNW, such as the effect of erosion for water treatment costs. Any proposal to retain forests social benefits, such as REDD+ initiative, should take into account the high cost forgone by forest owners when deciding the distribution of benefits of carbon sequestration. / Master of Science / Environmental services generate benefits for both private and public entities, which increases the complexity of calculating optimal levels for payment for environmental services (PES). A pilot PES project in the Yaque del Norte watershed of the Dominican Republic is an excellent example of this complexity; with benefits from upland forest conservation accruing to a hydroelectric company, a water supply company, and society at large. Reducing soil erosion through forest conservation can preserve dam capacity for hydro-electric power generation, preserve water quality and lower treatment costs, and reduce the global economic costs of CO₂ emissions. This study evaluates the socio-economic costs of forestland conservation in the Yaque del Norte catchment. The social benefits of carbon stored under forest land are compared to benefits under alternative land uses. In addition, forest land benefits from erosion prevention are estimated using a Universal Soil Loss Equation. Calculated benefits from forestland conservation are then compared to landuse opportunity cost estimates generated through a farm-level survey in the area. Study results show that the opportunity cost of forest conservation in the Yaque del Norte is high; ranging from between RD$10,000 and RD$200,000 per hectare per year. If society values carbon and soil retention as the direct benefits drawn from conserved forest, only lands with low very opportunity costs will be conserved. However, inclusion of the indirect external benefits of forestland conversion suggests that in many cases forest conservation generates greater social benefits than the private benefits associated with alternative land uses from conversion. PES payment levels of RD$5,000/ha/yr that internalize these external social benefits to forest land holders appear to be sufficient to preserve a significant share of current land and generate net social benefits. Further, part of the costs of these PES payments can be borne by hydro-electric and water companies, as they benefit directly from forest land conservation.

Digital satellite remote sensing and Geographic Information Systems (GIS) have been used effectively to determine the Universal Soil Loss Equation (USLE) output for a number of North Texas watersheds. This method involves determining the values of each of the USLE factors and using these factors as information layers within the GIS.