Estimating erosion in a riverine watershed bayou liberty-tchefuncta river in louisiana

GOAL, SCOPE, BACKGROUND: Sheet erosion from agricultural, forest and urban lands may increase stream sediment loads as well as transport other pollutants that adversely affect water quality, reduce agricultural and forest production, and increase infrastructure maintenance costs. This study uses spatial analysis techniques and a numerical modeling approach to predict areas with the greatest sheet erosion potential given different soils disturbance scenarios. METHODS: A Geographic Information System (GIS) and the Universal Soil Loss Equation (USLE) were used to estimate sheet erosion from 0.64 ha parcels of land within the watershed. The Soil Survey of St. Tammany Parish, Louisiana was digitized, required soil attributes entered into the GIS database, and slope factors determined for each 80 x 80 meter parcel in the watershed. The GIS/USLE model used series-specific erosion K factors, a rainfall factor of 89, and a GIS database of scenario-driven cropping and erosion control practice factors to estimate potential soil loss due to sheet erosion. RESULTS AND DISCUSSION: A general trend of increased potential sheet erosion occurred for all land use categories (urban, agriculture/grasslands, forests) as soil disturbance increases from cropping, logging and construction activities. Modeling indicated that rapidly growing urban areas have the greatest potential for sheet erosion. Evergreen and mixed forests (production forest) had lower sheet erosion potentials; with deciduous forests (mostly riparian) having the least sheet erosion potential. Erosion estimates from construction activities may be overestimated because of the value chosen for the erosion control practice factor. CONCLUSIONS: This study illustrates the ease with which GIS can be integrated with the Universal Soil Loss Equation to identify areas with high sheet erosion potential for large scale management and policy decision making. RECOMMENDATIONS: The GIS/USLE modeling approach used in this study offers a quick and inexpensive tool for estimating sheet erosion within watersheds using publicly available information. This method can quickly identify discrete locations with relatively precise spatial boundaries (approximately 80 meter resolution) that have a high sheet erosion potential as well as areas where management interventions might be appropriate to prevent or ameliorate erosion.     

Simulation of the cyclical process of heathlands: induction of mosaic structures, evolution to irreversible states

A simulation (random process with a discrete control of time) of cyclical regeneration of the monospecific heathlands established on the volcanic Chaîne des Puys (Massif Central, France) after the general and sudden surrender of grazing in the middle of this century, is proposed. On the high sloping zones on the south and south-west, spontaneous regressive dynamics of the heathlands appears, causing intense erosion. In other cases, some mosaic structure (Calluna vulgaris-Brachypodium pinnatum) cover the volcanoes. This highly simplified model takes into account the following processes: (i) the senescence process and vegetative reproduction of Calluna, (ii) the reproduction and intraspecific competition of Pinus sylvestris, (iii) erosion. The main results demonstrate that such a system exhibits an oscillatory behaviour. This phenomenon is strongly dependent on the initial parameters of the Calluna populations and may or may not reach an interior equilibrium: a stationary phase. An activity state function, taking into account the average transformation rapidity and modifications with constant surfaces, allows following the whole activity of the system. The origin of the mosaics could lie in this behaviour and could be more clearly topologic than strictly ecological. The oscillatory behaviour induces a multiple-steps settlement by pines. The suspension of grazing in several times would favour the health colonization by multimodal age-population of Calluna and then lessen the oscillations as well as erosion and regularizes pine colonization. The optimal density of the initial pool of pines seems to be equivalent to 1 tree per 700 m².     

酸雨对混凝土建筑物和文物损坏机理的研究

介绍了酸雨对混凝土建筑物和文物损坏机理的宏观分析,水泥中加入少量石膏,可延缓凝结时间,但当加入量大,将引起水泥膨胀,以致溃裂,探讨了酸雨对混凝土建筑物与文物损坏的微观分析,特别是酸雨等生成各种硫酸盐,通过从化学反应原理上分析了酸雨中二氧化硫与混凝土中钙离子反应生成石膏机理,从石膏特性上探讨了酸雨对混凝土建筑物和文物侵蚀机制,并由此提出了酸雨条件下保护混凝土建筑物和文物应对措施。     

Numerical investigation of flow erosion and flow induced displacement of gas well relief line

High-pressure particle-laden gas flow should be discharged through relief line of gas well timely to ensure safe test and exploitation. Erosion and vibration usually take place on the bend in relief lines, bringing a potential safety hazard to field operation. The majority of this paper investigates the factors affecting the erosion of bend and displacement of relief line in the downstream of bend using the computational fluid dynamics (CFD) methodology. A three-dimensional elbow pipe is selected as computational domain in this investigation. The kinematics and trajectory of discrete solid particles and liquid droplets are described by discrete phase model (DPM) while the hydrodynamic characteristics of continuous phase are obtained based on Reynolds-Averaged-Navier-Stokes (RANS) equations. An empirical erosion model is employed to predict the erosion rate of bend, and a fluid–structure interaction (FSI) model is adopted to calculate the displacement of relief line. The effects of types of multiphase flow (such as gas–solid two-phase flow and gas–liquid–solid three-phase flow), inlet flow rate and pipe diameter on erosion and displacement are discussed. The results show that large displacement and severe erosion present with large inlet flow rate in minor diameter pipe. The increase in liquid droplet content has less effect on flow erosion than that by the same increase in sand particle content.     

Effect of Human Activities on Overall Trend of Sedimentation in the Lower Yellow River,China

The Yellow River has been intensively affected by human activities, particularly in the past 50 years, including soil–water conservation in the upper and middle drainage basin, flood protection in the lower reaches, and flow regulation and water diversion in the whole drainage basin. All these changes may impact sedimentation process of the lower Yellow River in different ways. Assessing these impacts comprehensively is important for more effective environmental management of the drainage basin. Based on the data of annual river flow, sediment load, and channel sedimentation in the lower Yellow River between 1950 and 1997, the purpose of this paper is to analyze the overall trend of channel sedimentation rate at a time scale of 50 years, and its formative cause. It was found in this study that erosion control measures and water diversion have counteractive impacts on sedimentation rate in the lower Yellow River. Although both annual river flow and sediment decreased, there was no change in channel sedimentation rate. A regression analysis indicated that the sedimentation in the lower Yellow River decreased with the sediment input to the lower Yellow River but increased with the river flow input. In the past 30–40 years, the basin-wide practice of erosion and sediment control measures resulted in a decline in sediment supply to the Yellow River; at the same time, the human development of water resources that required river flow regulation and water diversion caused great reduction in river flow. The former may reduce the sedimentation in the lower Yellow River, but the reduction of river flow increased the sedimentation. When their effects counterbalanced each other, the overall trend of channel sedimentation in the lower Yellow River remained unchanged. This fact may help us to better understand the positive and negative effects of human activities in the Yellow River basin and to pay more attention to the negative effect of the development of water resources. The results of this study demonstrate that, if the overuse of river water cannot be controlled, the reduction of channel sedimentation in the lower Yellow River cannot be realized through the practice of erosion and sediment control measures.     

Soil-erosion and runoff prevention by plant covers in a mountainous area (se spain): Implications for sustainable agriculture

In the Mediterranean region the intensities and amounts of soil loss and runoff on sloping land are governed by rainfall pattern and vegetation cover. Over a two-year period (1998–1999), six wild species of aromatic and mellipherous plants (Thymus serpylloides subsp. Gadorensis, Thymus baeticus Boiss, Salvia lavandulifolia Vahl., Santolina rosmarinifolia L., Lavandula stoechas L. and Genista umbellata Poiret) were selected for erosion plots to determine their effectiveness in reducing water erosion on hillslopes of the Sierra Nevada Mountain (SE Spain). The erosion plots (including a bare-soil plot as control), located at 1,345 m in altitude, were 2 m² (2 m × 1 m) in area and had 13% incline. The lowest runoff and soil erosion rates, ranging from 9 to 26 mm yr⁻¹ and from 0.01 to 0.31 Mg ha⁻¹ yr⁻¹, respectively, over the entire study period, were measured under the Thymus serpylloides. Lavandula stoechas L. registered the highest rates among the plant covers tested, runoff ranging from 77 to 127 mm yr⁻¹ and erosion from 1.67 to 3.50 Mg ha⁻¹ yr⁻¹. In the bare-soil plot, runoff ranged from 154 to 210 mm yr⁻¹ and erosion from 4.45 to 7.82 Mg ha⁻¹ yr⁻¹. According to the results, the lowest-growing plant covers (Thymus serpylloides and Salvia lavandulifolia Vahl.) discouraged the soil erosion and runoff more effectively than did the taller and open medium-sized shrubs (Santolina rosmarinifolia L., Genista umbellata Poiret, Thymus baeticus Boiss and Lavandula stoechas L.). Monitoring allowed more direct linkage to be made between plant covers and the prevention of erosion, with implications for sustainable mountain agriculture and environmental protection.     

Soil erosion response to climatic change and human activity during the Quaternary on the Loess Plateau, China

We review published stratigraphic, archaeological and pedosedimentary evidence in order to reconstruct the history of soil erosion in China. Documentary evidence of climatic and flood events of the Yellow River and modern hydrological and meteorological data are synthesised to analyse the history of past human activity and its effects on soil erosion intensity during four nested periods of time during the Quaternary. The most intensive period of erosion during the Quaternary was in the Holocene. During the Holocene, intervals of intensive soil erosion occurred at 7500–7000 BP, 200 BCE–0 CE, 1000–1600 CE (Christian era) and during the 1930s, 1950s and the later part of the 1960s of the last century. Large-scale human activity including warfare during early Chinese history, population migration, the inner wars in 1930s, the Cultural Revolution and the recent national campaign to aid soil and water conservation are all closely related to the rate of soil erosion on the Loess Plateau and to sediment loads in the Yellow River. Overall, soil erosion during the transition from dry-cool to wet-warm climates was more intense than during wet-warm and cool-dry climatic episodes, but serious accelerated soil erosion has occurred during the last 2,500 years because of man-induced devastation of vegetation and other anthropogenic disturbance of the environment. Modern rates of soil erosion on the Loess Plateau are a combination of both intensive natural and human-induced erosions and are some four times greater than occurred in the geological past. The recent implementation of soil and water conservation measures has decreased sediment load in the Yellow River by 25%.     

The use of bio-waste to revegetate eroded land areas in Ylläs,Northern Finland: Toward a zero waste perspective of tourism in the Finnish Lapland

Lapland is one of the most attractive nature-tourism areas in Europe, and tourism is vital for local economy. However, recreational tourist activities such as skiing, hiking and horse riding deteriorate the unique and vulnerable nature of Northern Finland. Erosion and wearing of tourist areas negatively affects biodiversity and ecosystem services and reduce the attractiveness of the region. Tourism is also the source of other environmental disturbances such as wastes. Currently, in Lapland, the prevalent waste treatment method is disposal, and wastes are transported over long distances due to lack of recipient facilities for waste management. The suggestion for sustainable waste management Scenario presented in this paper is to find a synergistic solution to both of these problems, by local treatment of bio-waste in an anaerobic digestor and utilization of digestate to revegetate eroded land. It is proposed that bio-waste is co-digested with sewage sludge and offal from slaughterhouses in Ylläs in the municipality of Kolari. An estimated 500–1000 t of digestate could be produced and used in tourist areas annually. Experiences from existing seasonal bio-waste collection schemes and interviews of local tourist enterprises and tourists indicate that there is willingness to extend the source separation of wastes. Assessment of the digestion Scenario suggests that economic costs of investment could be offset by avoided costs and by additional environmental and social benefits. It is concluded that this zero waste approach could lead to an improved image of Lapland as a sustainable tourist destination.     

Risk Management of Sediment Stress: A Framework for Sediment Risk Management Research

Research related to the ecological risk management of sediment stress in watersheds is placed under a common conceptual framework in order to help promote the timely advance of decision support methods for aquatic resource managers and watershed-level planning. The proposed risk management research program relies heavily on model development and verification, and should be applied under an adaptive management approach. The framework is centered on using best management practices (BMPs), including eco-restoration. It is designed to encourage the development of numerical representations of the performance of these management options, the integration of this information into sediment transport simulation models that account for uncertainty in both input and output, and would use strategic environmental monitoring to guide sediment-related risk management decisions for mixed land use watersheds. The goal of this project was to provide a sound scientific framework based on recent state of the practice in sediment-related risk assessment and management for research and regulatory activities. As a result, shortcomings in the extant data and measurement and modeling tools were identified that can help determine future research direction. The compilation of information is beneficial to the coordination of related work being conducted within and across entities responsible for managing watershed-scale risks to aquatic ecosystems.     

Environmental effects of soil property changes with off-road vehicle use

The effects of off-road vehicles (ORVs) on the physical and chemical properties of 6 soil series were measured at Hollister Hills State Vehicular Recreation Area in central California. Accelerated soil erosion and the alteration of surface strength, bulk density, soil moisture, temperature, and soil nutrients were quantified to gain an insight into the difficulty of revegetating altered, or modified, areas.Erosion is severe at Hollister Hills, particularly in coarse grained soils on steep slopes. Erosion displaced 0.5 and 3.0 metric tons per square meter on 2 trails on gravelly sandy loam, and 0.3 metric tons/m² from a trail on sandy loam. The surface strength and bulk density increased while the soil moisture decreased in gravelly sandy loam, coarse sandy loam, sandy loam, and clay. Clay loam had an increased surface strength with variably increased bulk density and no decrease in soil moisture. Diurnal temperature fluctuations increased and organic material and soil nutrients decreased in soil modified by vehicles.These property changes increase the erosion potential of the soil, impede germination of seedlings, and slow natural revegetation. Management methods in ORV-use areas should include planning trails by prior application of the universal soil loss equation and soil surveys, trail closure before complete loss of the soil mantle, and revegetation of closed areas.