Hillslope Runoff and Soil Erosion Following Reforestation in the Copper Basin,Tennessee, USA

The landscape of the 130 km² Copper Basin, in the southeastern USA, became extremely degraded during more than a century of logging, mining, acidification, grazing, and fire. In the twentieth century, the Copper Basin became the focus of a series of reforestation programs and is now largely tree‐covered again. To investigate the effects of over 50 years of reforestation efforts, we developed a space‐for‐time substitution and conducted rainfall simulation experiments in ‘forest’ patches of various ages, at sites remaining unvegetated, and at forested reference sites outside the basin. At 59 sites, we monitored surface runoff and sediment detachment rates during 30‐minute rainfall simulation experiments; and at 54 of those sites, we determined soil organic matter content. Then, we measured litter and observed soils at 25 of the sites, and measured soil respiration at a site in each age zone. The results demonstrate that soil erosion by sediment detachment decreases within a decade following reforestation. Recently reforested sites have soils with significantly less organic matter and have higher runoff rates than forests more than 50 years old. The long‐term persistence of low infiltration rates suggests that, at sites where the A and B soil horizons and the biological health of the soil have been lost, restoration of the hydrologic function of a landscape by reforestation may require centuries.     

Estimation of Soil Erosion Using Field and Modelling Approaches in an Undisturbed Arnhem Land Catchment,Northern Territory,Australia

An assessment of slope erosion at Tin Camp Creek catchment, Arnhem Land, Northern Territory, Australia, was carried out using the fallout environmental radioisotope caesium‐137 (¹³⁷Cs) as an indicator of soil erosion status, two numerical models (SIBERIA and the Revised Universal Soil Loss Equation (RUSLE)) and erosion pins. This undisturbed drainage basin is situated in the seasonally wet‐dry tropics, with high energy storms and a mean annual rainfall of 1389 mm. Tin Camp Creek catchment is unaffected by European agriculture or pastoral activities, but often experiences fire during the dry season. Two transects were sampled for ¹³⁷Cs in 2002 and 2004, and two models were used to convert ¹³⁷Cs measurements into soil loss estimates. Two methods using the theoretical Profile Distribution Model (PDM) gave net soil redistribution rates between +2.72 and –22.19 t ha^?1 yr^?1 and +2.95 and –24.06 t ha^?1 yr^?1, respectively, while an Australian empirical model (AEM) for uncultivated soils produced estimates between +1.84 and –7.00 t ha^?1 yr^?1 (negative values indicate soil erosion, positive, deposition). The RUSLE gave estimated soil losses for the two transects of approximately 10 t ha^?1 yr^?1, while the SIBERIA model produced values between 0.5 and 2 t ha^?1 yr^?1 for the transects and between 3.5 and 11 t ha^?1 yr^?1 for the total catchment. Average net soil losses of 14 and 15 t ha^?1 yr^?1 for the total catchment and slopes, respectively, were measured by erosion pins. The soil losses in the catchment are similar to those for some other transects in the Northern Territory and the Kimberley region of Western Australia (measured by the ¹³⁷Cs AEM), even though these areas are affected by pastoral activities. This may be at least partly explained by erosion in Tin Camp Creek catchment during high intensity rainstorms at the commencement of the wet season, especially if the slopes have been affected by fire during the previous dry season.     

The Role of Fire Disturbance on Runoff and Erosion Processes – a Long‐Term Approach,Mt. Carmel Case Study,Israel

The Mediterranean ecosystem of Mt. Carmel, Israel, is subjected to an increasing number of forest fires of various extents and severities. The impacts of forest fires on runoff and erosion are widely documented and include increased peak flows and soil loss until the return of a vegetation cover. Most studies, however, treat fire as a single event, whereas the present study is aimed at exploring the long‐term effects of repeated forest fires on eco‐geomorphic processes. The study integrates the results of plot‐based, detailed analysis of post‐fire runoff and erosion with vegetation recovery analysis, at a temporal‐spatial scale which includes the effect of reburning. Our results indicate that forest fires lead to a significant increase in runoff and sediment yields, particularly during the first two years following the disturbance, up to five orders of magnitude higher than from the adjacent unburnt control plots.     

Development of Trigger Levels to Assess Catchment Disturbance on Stream Suspended Sediment Loads in the Magela Creek Catchment,Northern Territory,Australia

Trigger levels for fine suspended sediment (FSS) load in streams are required to identify rainfall-runoff events that have significantly elevated FSS loads, compared with expected background loads, as a result of catchment disturbance. Stream FSS load data collected in the mine-impacted Magela Creek catchment in the wet-dry tropics were used to derive water quality management trigger levels for two approaches – a Before-After-Control-Impact Paired difference design (BACIP) and a regression relationship between observed FSS load and corresponding event discharge characteristics. The results indicate that both the BACIP and regression relationship approaches behave similarly, with similar FSS load events elevated above trigger levels. Notwithstanding this, it is recommended that in order to reliably assess the location and magnitude of a catchment disturbance on FSS load, a combination of BACIP and regression relationship approaches must be adopted. In this study, an event with a FSS load above trigger levels associated with both BACIP and the regression relationship fitted for the downstream site is considered to be significantly elevated as a result of a disturbance within the mine-impacted region. While this technique cannot conclusively determine whether the cause of the disturbance is mine-related or natural (such as fire or bank erosion), it is an efficient statistical method of identifying events that warrant further investigation and management action, if required.     

陕北明长城夯土密度与雨蚀破坏的量化研究

为量化研究夯土性质对陕北明长城遗址雨蚀破坏模式的影响作用,采用室内模拟降雨试验的方法对夯土密度和雨蚀量间的关系进行定量化分析。研究结果显示,大到暴雨条件下,干湿作用产生的破坏是低强度夯土(密度1.5 g·cm^-3、1.6 g·cm^-3)最主要的雨蚀破坏模式,冲刷破坏造成的雨蚀量较小;水力侵蚀产生的冲刷破坏和重力侵蚀引起的小范围掉块是高强度夯土(密度1.7~1.9 g·cm^-3)最主要的破坏模式,冲刷破坏造成的雨蚀量较大;当土体含水率在3%~7%区间时,夯土的雨蚀量和密度呈指数函数关系,二者呈现正相关性。研究结果为探索多因素作用下夯土雨蚀的破坏机制提供方法借鉴,是土遗址病害研究的重要组成部分。     

Fire,Humans and Denudation at Wangrah Creek,Southern Tablelands,N.S.W.

The influence of altered fire regimes on the denudation of a catchment is determined from alluvial deposits of the last 10,000 yrs and by monitoring runoff and erosion before and after a wildfire. An increase in fire frequency beginning at 3,000–4,000 yrs BP, as a result of intensified Aboriginal burning, did not change the mechanisms or rates of denudation nor did it cause widespread alluviation as suggested by others. The results of monitoring show that before and after mild fires there is insufficient runoff on most slopes to entrain sediment. Only after intense fires are runoff and erodibility increased enough to significantly accelerate erosion. Conditions are then identified which are most likely to lead to accelerated erosion from altered fire regimes in other catchments.     

Erosion and Errors: Testing the Use of Repeated LIDAR Analyses and Erosion Modelling for the Assessment and Prediction of Erosion of Archaeological Sites?

Slope soil erosion is one of the main threats to archaeological sites. Several methods were applied to establish the erosion rates at archaeological sites. Digital elevation models (DEMs) from three different dates were used. We compared the elevations from these three models to estimate erosion. We also applied the landscape evolution model LAPSUS with the available DEMs as basis. Spatial processing errors and effects of tillage and harvesting practices explain most of the DEM elevation differences between the recordings. Increased DEM resolution does not result in more precise or reliable erosion. The present technological level of landscape evolution modelling makes it possible to indicate areas most vulnerable to soil displacement by surface runoff erosion and tillage. Future research, using sediment and surface dating techniques such as deposit of radionuclides, heavy metals and OSL dating will provide a more accurate estimation of erosion rates and the subsequent impact on archaeological sites.     

The Potential Relationship Between Archaeological Artifact Exposure and Surface Geomorphic Processes: Northeastern Peloponnese,Greece

Complex interactions between topography, near-surface geology, active tectonics, climate, and human activity shape a landscape, conditioning archaeological deposits and making sediment deposits from surface erosion important archives. There is a potential relationship between the intensity of geomorphic processes and surface artifact distribution. This study assesses the potential relationship between soil erosion by water and the spatial distribution of archaeological surface artifacts in the Inachos River watershed, Greece. The mountainous, semi-arid Mediterranean region is particularly vulnerable to soil loss. Soil erosion is quantified by applying the Revised Universal Soil Loss Equation in a GIS framework. Estimates of soil loss vary spatially compared to surface artifact finds of the pedestrian survey of the Western Argolid Regional Project. A statistically significant relationship is identified between surface erosion rates and artifact density. Preferential topography for occupation suggests this is an associative rather than causative relationship. Knowledgeable interpretation of artifact distribution enables accurate reconstruction of human settlement history.     

Archaeobotany of fruit seed processing in a monsoon savanna environment: evidence from the Keep River region,Northern Territory,Australia

We analyse archaeobotanical remains from three excavated rockshelter sites, Jinmium, Granilpi and Punipunil, in the Keep River region, northwestern Australia. The record is dominated by burnt fragmented seed remains from the fruit trees Persoonia falcata and Buchanania obovata, consistent with ethnographic records of whole fruits being pounded into pastes and cakes at the beginning of the summer wet season. Surface seed samples of non-cultural origin are mostly whole and unburnt, and contain higher proportions of grass seeds. Sustained processing of fruit seeds is first visible in the archaeological record about 3500 years ago. Spatial and temporal variation in its intensity is evident since that time until it declines following European colonisation. The decline does not represent total site abandonment, but a reorientation of activities following the ecological and social changes that came with pastoralism. The former included the local decline of P. falcata with more intense fire regimes.     

降雨对陕西省榆林市榆阳区明长城破坏的初步分析

降雨是陕西省榆林市榆阳区明长城的主要破坏因素之一。调查中发现,降雨对遗址破坏严重。为了研究降雨对遗址的破坏,在对遗址详细调查的基础上,结合遗址特征与遗址区降雨特点,并参考土壤侵蚀学等方面理论,分析了降雨对遗址的破坏形式及影响因素。结果表明,降雨对遗址的破坏形式可分为直接破坏和间接破坏两大类。其中,主要破坏形式为冲沟侵蚀、片流面蚀和雨蚀剥离。影响因素包括降雨特点、遗址形态、土的性质、植物生长状况和地幔层等,不同破坏形式的主要影响因素各有不同。本结果不仅丰富了降雨对土遗址破坏方面的研究,还为后续陕西榆阳区明长城保护加固措施的选择提供了依据。     

Changing Fire Management in the Pastoral Lands of Cape York Peninsula of northeast Australia, 1623 to 1996

Accounts of European explorers between 1623 and 1880 indicate that fires were lit by Aboriginal people on Cape York Peninsula in northeast Australia throughout the dry season (May–October). Diaries kept by three generations of pastoralists in the Musgrave area (1913–1952, 1953–1974 and 1976–1992) show that burning activities were largely confined to a two to six week period between May and early August. The timing of burning depended on the amount and date of cessation of wet season rainfall. More rarely, ‘storm‐burning’, burning under hot conditions within a few days of the first heavy rains of the wet season, was undertaken. Long‐term pastoralists felt a responsibility to use fire wisely and had a detailed knowledge of the role of fire in land management. Their decisions to burn were based on the extent of grass curing, and soil and weather conditions, all of which affected the extent of each burn. They used early dry season fires mainly to maintain forage and control cattle movements. Storm‐burns were reputed to control woody weeds, but were used infrequently because of difficulty in controlling their spread and uncertainty as to when the next rains would stimulate new grass growth.     

Assigning Context to Artifacts in Burned-Rock Middens

Abstract

Accumulations office-cracked rock and carbon-stained sediment in pits mark locations of past cooking and heating facilities around the world. While the specific functions of these features may vary, the use of stones as heating elements in earth ovens is common. After repeated use, debris in the form of fire-cracked stones, charcoal, ash, sediment, carbonized plant fragments, and other materials accumulates to form low mounds known in the U.S. Southern Plains and the Southwest as burned-rock middens. The middens may include artifacts some introduced inadvertently with sediment used to form an earthen cap to seal the pit oven. The sediment and included artifacts for this insulating cap may be borrowed from other parts of the site. After the cooking is complete, the earthen cap is peeled open and all materials redistributed by trampling and slope wash. Artifacts and other materials in burned-rock middens, therefore, may not represent discrete events or periods directly associated with use of the ovens.     

Erosion and Nutrient Loss on Sloping Land under Intense Cultivation in Southern Vietnam

To help improve the well‐being of the local people, a joint Vietnamese‐UK team set out to establish a way of estimating soil and nutrient losses under different land management scenarios, using field data extrapolated through remote sensing and GIS, to obtain catchment‐wide estimates of the impact of land cover change. Immigration from remote provinces to the Dong Phu District of Binh Phuóc Province, about 120 km north of Ho Chi Minh City, has led to disruption of soil surface stability on easily eroded clayey sandstones, creating rapid nutrient depletion that affects crop yields and siltation in the channel of the Rach Rat river downstream. The poor farmers of the areas see crop yields drop dramatically after two or three years of cultivation due to the fertility decline. Soil loss varies dramatically between wet season and dry season and with ground cover. Erosion bridge measurements showed a mean loss of 85.2 t ha^?1 y^?1 under cassava saplings with cashew nuts, 43.3 t ha^?1 y^?1 on uncultivated land and 41.7 t ha^?1 y^?1 under mature cassava. The rates of erosion were higher than those reported in many other parts of Vietnam, reflecting the high erodibility of the friable sandy soils on the steep side‐slopes of the Rach Rat catchment. However, although the actual measurements provide better soil loss data than estimates based on the parameters of soil loss equations, a large number of measurement sites is needed to provide adequate coverage of the crop and slope combinations in this dissected terrain for good prediction using GIS and remote sensing.     

Methods for assessing stormwater management at archaeological sites: Copan Ruins case study

Archaeological sites may be discovered by fortuitous soil erosion, but their protection requires deliberative stormwater management plans and estimates of runoff volumes. This paper uses the Maya site of Copan, Honduras to demonstrate widely applicable methods to estimate runoff, including use of satellite rainfall data processed by single parameter models. Our analysis compares present day estimates of runoff and erosion with those of two historic periods, 900 A.D during peak Maya occupation of the Great Plaza, and 1800 A.D. prior to excavation when the site was mostly forest covered. For each period, the watershed area, soil, land cover, and rainfall data were used with a single parameter Curve Number model to estimate the runoff volume for annual to decadal storms. The maximum runoff depth and erosive potential in conveyance channels was then computed with the HEC-RAS model. The models did not predict runoff would occur for the forested period of 1800 A.D., but predicted that runoff for 900 and post-1800 A.D was large enough to cause the erosion observed in the drainage channel today. Our results provide runoff magnitudes that demonstrate the need for Copan Maya designed stormwater removal infrastructure described in earlier archaeological analysis. The need for stormwater removal was also designed into the wet Maya site of Palenque, while stormwater capture and storage was designed into the Maya sites of Tikal, a drier site due to local drainage characteristics and water availability. Methods used in stormwater runoff analysis can empower communities and managers to develop scientifically and culturally appropriate non-structural management methods to conserve archaeological sites.     

Managing Environmental Impacts of Recreation and Tourism in Rainforests of the Wet Tropics of Queensland World Heritage Area

This paper describes environmental impacts of tourism and recreation activities in the world heritage listed rainforests of northeast Australia and presents management strategies for sustainable visitor use of the protected area. Tropical rainforests are characterised by their low resistance and moderate to high resilience to impacts associated with human visitation. Visitor use in the World Heritage Area is mostly associated with walking tracks, camping areas, day use areas and off‐road vehicle use of old forestry roads and tracks. Adverse environmental impacts range from vegetation trampling, soil compaction, water contamination and soil erosion at the local scale through to spread of weeds, feral animals and soil pathogens along extensive networks of old forestry roads and tracks at the regional scale. Concentration of visitor use is the most desirable management strategy for controlling adverse impacts at most World Heritage Area visitor nodes and sites, and includes methods such as site hardening and shielding to contain impacts. For dispersed visitor activities, such as off‐road vehicle driving and long‐distance walking, application of best practice methods by the tourist industry and recreational users such as removal of mud and soils from vehicle tyres and hiking boots before entering pathogen‐free catchments, together with seasonal closure of roads and tracks, are the preferred management strategies. Retention of canopy cover at camping areas and day use areas, as well as along walking tracks and forestry roads is a simple, yet effective, management strategy for reduction of a range of adverse impacts, including dispersal of weeds and feral animals, edge effects, soil erosion and nutrient loss, road kill and linear barrier effects on rainforest fauna.     

Rugged Plateaus and Extensive Floodplains — Modelling Landform Evolution in a Northern Australian Catchment

Medium to large natural catchments are often more spatially heterogeneous than small catchments or single landforms. Attempting to model landform evolution of large areas is consequently more complex. This paper demonstrates that modelling landform evolution in medium to large catchments can be improved by calibrating the model to smaller, more geomorphologically homogenous sub‐catchments. The paper investigates landform evolution in the Ngarradj catchment in the Northern Territory of Australia (a medium scale catchment of approximately 67 km²). The catchment is complex and contains two distinct landform regions; an upland plateau region with highly dissected sandstone and shallow, sandy soils, and a lowlands region with gentle, wooded slopes and floodplains with deep, sandy soils. The SIBERIA landform evolution model is calibrated and applied to the Ngarradj catchment. The complexity of the Ngarradj catchment is incorporated into the modelling by dividing the catchment into three sub‐catchments (Swift Creek (SC), Upper Main (UM) and East Tributary (ET)) which are relatively homogeneous and for which hydrology and sediment transport data are available. A discharge‐area relationship and long‐term, sediment loss rates for the catchment are derived based on an annual series flood frequency analysis of a 20 year runoff record predicted in a previous study. Sediment transport modelling incorporates both suspended and bedload sediment loss. The denudation rates derived using these data are 37, 63 and 77 mm kyr^?1 for the SC, UM and ET sub‐catchments, respectively. Model predictions indicate that the UM sub‐catchment will have the greatest mean erosion. This is balanced by the large amount of deposition that will occur in the upper Ngarradj valley of the UM sub‐catchment. Further deposition occurs on the floodplain of Ngarradj, with the area between the SC and ET/UM (up‐stream) sub‐catchments experiencing a small net accretion of sediment (15 mm kyr^?1).     

The use of Caesium–137 to Assess Surface Soil Erosion Status in a Water–Supply Catchment in the Hunter Valley,New South Wales,Australia

In the absence of direct erosion measurements, the soil activity of the fallout radionuclide caesium–137 (¹³⁷Cs) offers an attractive tool for the estimation of long–term (approximately 45 years) net surface and minor rill soil erosion rates for hillslopes. A transect–based soil sampling technique was applied to one woodland and five grazed pasture hillslopes in the Williams River water–supply catchment in the Hunter Valley, New South Wales. An Australian regression model (SOILOSS) relating net soil loss from runoff–erosion plots to ¹³⁷Cs deficit in soils was used to calculate a weighted net surface and minor rill erosion rate for the six hillslopes. The net median surface erosion rates ranged between 0.00 and 0.64 t ha^–1yr^–1with the average median soil erosion rate of 0.19 t ha^–1 yr^–1(std. dev. = 0.23), indicating that these hillslopes were unlikely to be major sources of sediment to the catchment's waterways. Net soil loss rates were also shown to be low in comparison to Australia–wide data and comparable to hillslope data obtained elsewhere in the same region. Minimum and maximum error bounds were provided with each erosion rate to account for radionuclide detector count error. For one hillslope the estimated error due to detection was 1.34 t ha^–1yr^–1, while the remaining five hillslopes exhibited error of up to 0.41 t ha^–1yr^–1. Correlation analyses between the net soil loss rates and physical hillslope characteristics were non–significant.     

Basin‐Wide Sediment Grain‐Size Numerical Analysis and Paleo‐Climate Interpretation in the Shiyang River Drainage Basin

Basin‐wide sediment transport affects estimates of basin sediment yield, which is a fundamental scientific issue in drainage basin studies. Many studies have been conducted to examine erosion and deposition rates in drainage networks. In this study, we proposed a new approach using grain‐size standard deviation model of sedimentary samples from different geomorphological units for numerical analysis and paleo‐climate interpretation in the Shiyang River drainage basin, arid China. 1043 sedimentary samples were obtained from the upper reaches, the midstream alluvial plain and the terminal lake area; chronological frames were established based on 58 radiocarbon ages. Grain‐size standard deviation model was introduced to examine sediment components according to grain‐size and transport forces. In addition, transient paleo‐climate simulations, including the Community Climate System Model version 3 and the Kiel models, were synthesized, as well as the results from PMIP 3.0 project, to detect the long‐term climate backgrounds. Totally, we found four major common components, including fine particulates (<2 μm), fine silt (2–20 μm), sandy silt (20–200 μm), coarse sand (>200 μm), from basin‐wide sedimentary samples. The fine particulates and fine silt components exist in all the sedimentary facies, showing long‐term airborne aerosol changes and its transport by suspended load. There are some differences in ranges of sandy silt and coarse sand components, due to lake and river hydrodynamics, as well as the distance with the Gobi Desert. Paleo‐climate simulations have shown that the strong Asian summer monsoon during the transition of the Last Deglaciation and Holocene was conducive to erosion and transport of basin‐wide suspended load, also enhancing sediment sorting effects due to strong lake hydrodynamics. Our findings provide a new approach in research of long‐term basin‐wide sediment transport processes.     

Climate,vegetation and ecology during Harappan period: excavations at Kanjetar and Kaj,mid-Saurashtra coast,Gujarat

A multi-proxy study was carried out to address climate–culture relationship from two trenches one each from Kaj and Kanjetar (mid-Saurashtra coast) deposited in a lacustrine setting, since ∼1960 Cal BC and ∼2230 Cal BC, respectively. The salinity of aqueous soil solution (0.1 ppt) and fresh water thecamoebians in both the sites indicate fresh water depositional environment. But, an increase in salinity (0.2 ppt) in the top clayey sediment in Kanjetar is attributed to water evaporation through upward capillary action from moisture deficit exposed land. The fragments of ancient potteries and other artefacts recovered from the bottom sediment provide evidences of Sorath-Harappan colonization in the vicinity which was not an urban site. The abundant cyanobacterium remains, low terrigenous organic matter, aquatic pollen and low thecamoebians in bottom sediment indicates low precipitation and arid climatic conditions ∼2000 BC. During this period the dominance of evergreen and moist deciduous arboreals from both the sites do not show equilibrium with the prevailing dry/arid climate and therefore, the pollen assemblage here represents the remnants of wetter middle Holocene vegetation in the region. Phytoliths of drought-tolerant summer season crops also reflects here changes made in the agricultural strategy by Harappans in response to climate. The increase in deciduous arboreal pollen since the last ∼2000 years represents equilibrium with the dry/arid climate. But, enhanced limnic conditions recorded with the help of thecamoebians during this period is attributed to changes in wetland configuration induced by hydrostatic changes in the river mouth that was largely defined by the dynamics of sediment deposition through rain-fed rivers/streams in the region.     

Coastal Erosion and Site Destruction on Carriacou,West Indies

Abstract

Archaeological investigations on the island of Carriacou in the southern Lesser Antilles, west Indies, have revealed prehistoric sites dating from CAL A.D. 400 to 1400. Grand Bay is one of the largest and archaeologically richest sites on the island and in the region, but is rapidly succumbing to erosion from natural forces and human activities. A similar problem affects the site of Sabazan. Both sites are located on the windward east coast of the island and have been, or are currently, mined for sand; two hurricanes also occurred recently. Photographs and extensive mapping of Grand Bay and preliminary work at Sabazan indicate that both sites are eroding at an average rate of approximately 1 m per year along the lengths of their coastal profiles. These data, combined with a quantification of materials recovered from excavation at Grand Bay, indicate that the loss of cultural remains from natural and human causes is catastrophic and that these sites will likely be completely destroyed within the next two decades if erosion continues at its present rate.