High Water Levels Research Articles

Hedge funds trading strategies and leverage

We introduce learning into the hedge fund managers’ risk choice problem with imperfect information. We find that with a constant but unobserved expected return on investment, learning induces managers to take more risks and increases manager compensation. When the return is stochastic, learning increases manager compensation and induces an aggressive leverage choice when funds perform poorly or managers’ belief about fund returns is low. When funds are close to the high-water mark or the return belief is high, the learning effect reverses. This situation generates a flatter leverage ratio, which helps explain the cross-sectional dispersion of hedge fund strategies’ market betas. Finally, comparative statistics for transition intensity show that procyclicality in the hedge fund industry declines.

Robust leverage choice of hedge funds with rare disasters

We study the effects of hedge fund manager’s ambiguity aversion for jump and diffusion risks on the leverage policy under a high-water mark contract. We find that the jump risk has an inverted U-shaped effect on the leverage choice, which can be explained by the variance effect and skewness effect. Our result also indicates that diffusion ambiguity aversion has a larger negative impact on leverage than jump ambiguity aversion. Manager’s ambiguity aversion in jump risk amplifies the skewness effect when the price jump is positive. Our findings provide some insights into the risk taking strategy of hedge fund under ambiguity.

Production in peatlands: Comparing ecosystem services of different land use options following conventional farming

Majority of Dutch peatlands are drained and used intensively as grasslands for dairy farming. This delivers high productivity but causes severe damage to ecosystem services supply. Peatland rewetting is the best way to reverse the damage, but high water levels do not fit with intensive dairy production. Paludiculture, defined as crop production under wet conditions, provides viable land use alternatives. However, performance of paludiculture is rarely compared to drainage-based agriculture. Here, we compared the performances of six land use options on peatland following a gradient of low, medium, and high water levels, including conventional and organic drainage-based dairy farming, low-input grasslands for grazing and mowing, and high-input paludiculture with reed and Sphagnum cultivation. For each land use option, we conducted environmental system analysis on model farm system defined by a literature based inventory analysis. The analysis used five ecosystem services as indicators of environmental impacts with a functional unit of 1-ha peat soil. Ecosystem services included biomass provisioning, climate, water, and nutrient regulation, and maintenance of habitat. Results showed that drainage-based dairy farming systems support high provisioning services but low regulation and maintenance services. Organic farming provides higher climate and nutrient regulation services than its conventional counterpart, but limited overall improvement due to the persistent drainage. Low-intensity grassland and paludiculture systems have high regulation and maintenance services value, but do not supply biomass provisioning comparable to the drainage-based systems. Without capitalizing the co-benefits of regulation and maintenance services, and accounting for the societal costs from ecosystem disservices including greenhouse gas emission and nitrogen pollution, it is not likely that the farmers will be incentivized to change the current farming system towards the wetter alternatives. Sustainable use of peatlands urges fundamental changes in land and water management along with the financial and policy support required.

Performance of the flood warning system in Germany in July 2021 – insights from affected residents

Abstract. In July 2021 intense rainfall caused devastating floods in western Europe and 184 fatalities in the German federal states of North Rhine-Westphalia (NW) and Rhineland-Palatinate (RP), calling into question their flood forecasting, warning and response system (FFWRS). Data from an online survey (n=1315) reveal that 35 % of the respondents from NW and 29 % from RP did not receive any warning. Of those who were warned, 85 % did not expect very severe flooding and 46 % reported a lack of situational knowledge on protective behaviour. Regression analysis reveals that this knowledge is influenced not only by gender and flood experience but also by the content and the source of the warning message. The results are complemented by analyses of media reports and official warnings that show shortcomings in providing adequate recommendations to people at risk. Still, the share of people who did not report any emergency response is low and comparable to other flood events. However, the perceived effectiveness of the protective behaviour was low and mainly compromised by high water levels and the perceived level of surprise about the flood magnitude. Good situational knowledge and a higher number of previously experienced floods were linked to performing more effective loss-reducing action. Dissemination of warnings, clearer communication of the expected flood magnitude and recommendations on adequate responses to a severe flood, particularly with regard to flash and pluvial floods, are seen as major entry points for improving the FFWRS in Germany.

Dharan Water Supply System - Alarming Issues and Future

This study examines the critical issue of water scarcity in the Dharan Sub-metropolitan city, analyzing the various factors that are driving factors driving water demand and proposing strategies and ensuring water security. This study finds that factors replace with the rapid expansion of residential areas, increasing population, steeper slopes, changing lifestyles, natural hazards, technical and management leakage are major contributors to the growing water shortages in the area, leading to a situation of water instability. However, the study also identifies that factor such as precipitation, geology, soil types, potential water sources in the area offer opportunities for stabilizing the water supply in Dharan Sub-metropolitan. This study highlights the combined effect of these various active factors that led to an increase in per capita demand of water from 71 to 100 lpcd. This increasing water demand and shrinking of surface water led to Interrupted Water pumping and overexploitation. Additionally, the study indicates that due to high level of Non-Revenue Water (NRW) up-to 40%, certain parts of the city’s residents are facing major difficulties in accessing clean drinking water. The study also finds that positive changes in precipitation, supportive soil types and geology in the city of Dharan increases the potential for water recharge and harvesting. In order to achieve a sustainable and climate-resilient water supply, the study recommends implementing Water management tools likewise protective measures for critical water zones, stabilizing stream banks and gullies for surface water source improvement, artificial recharge of the city through Climate Adaptive Recharge Pits (CARP) and slope interception methods, as well as community-based water harvesting for groundwater source improvement. Furthermore, the study suggests establishing R&D unit involving national and local level experts and stakeholders for better planning and management.

Sulfur: a neglected driver of the increased abundance of antibiotic resistance genes in agricultural reclaimed subsidence land located in coal mines with high phreatic water levels

Due to the shallow burial of groundwater in coal mines with a high phreatic water level, a large area of subsidence lakes is formed after the mine collapses. Agricultural and fishery reclamation activities have been carried out, which introduced antibiotics and exacerbated the contamination of antibiotic resistance genes (ARGs), but this has received limited attention. This study analyzed ARG occurrence in reclaimed mining areas, the key impact factors, and the underlying mechanism. The results show that sulfur is the most critical factor impacting the abundance of ARGs in reclaimed soil, which is due to changes in the microbial community. The species and abundance of ARGs in the reclaimed soil were higher than those in the controlled soil. The relative abundances of most ARGs increased with the depth of reclaimed soil (from 0 to 80 cm). In addition, the microbial structures of the reclaimed and controlled soils were significantly different. Proteobacteria, was the most dominant microbial phylum in the reclaimed soil. This difference is likely related to the high abundance of sulfur metabolism functional genes in the reclaimed soil. Correlation analysis showed that the differences in ARGs and microorganisms in the two soil types were highly correlated with the sulfur content. High levels of sulfur promoted the proliferation of sulfur-metabolizing microbial populations such as Proteobacteria and Gemmatimonadetes in the reclaimed soils. Remarkably, these microbial phyla were the main antibiotic-resistant bacteria in this study, and their proliferation created conditions for the enrichment of ARGs. Overall, this study underscores the risk of the abundance and spread of ARGs driven by high-level sulfur in reclaimed soils and reveals the mechanisms.

Dangerous Ground: Squatters, Statesmen, And The Antebellum Rupture of American Democracy by John Suval

Reviewed by: Dangerous Ground: Squatters, Statesmen, And The Antebellum Rupture of American Democracy by John Suval Kenneth R. Coleman DANGEROUS GROUND: SQUATTERS, STATESMEN, AND THE ANTEBELLUM RUPTURE OF AMERICAN DEMOCRACY by John Suval Oxford University Press, New York, 2022. Illustrations, notes, bibliography, index. 296 pages. $35.00 cloth. In his first book, John Suval makes a novel contribution to the literature on settler colonialism (and Civil War causation) by replacing the term “settler” with a largely overlooked nineteenth-century term for the hordes of farmers, planters, and speculators who ventured west to occupy land without legal title: squatters. In the 1830s, Andrew Jackson’s new Democratic Party rebranded squatters from lawless interlopers to Indian-fighting heroes who enlarged the nation at little cost to the federal government. Democratic politicians promoted land-for-votes policies that allowed squatters to bypass auctions and purchase the land they occupied at fixed prices. This strategy, deeply rooted in White supremacy, allowed the Democrats to forge a national coalition of planters, farmers, and immigrants that transcended social class. But according to Suval, a specter haunted this squatter-statesman alliance: slavery. The emergence of the Free Soil ideology among many squatters put them at odds with pro-slavery Democratic politicians. Suval argues that this contradiction, at the heart of what he calls Squatter Democracy, led directly to Bleeding Kansas, the fracturing of the Democratic Party, and the Civil War itself. In the book’s early chapters, Suval describes how squatters transitioned from figures of scorn to veneration. In the early republic, most Federalists abhorred squatters for intruding on public land they envisioned as a future source of revenue for nation building. With the rise of Jackson, many elites promoted squatters as a cost-effective means to clear land for future settlements. Democratic politicians promoted pre-emption legislation that worked in conjunction with Indian removal policies, ensuring that White men would dominate Jacksonian Democracy and the American West itself. Even the Whig Party, founded in opposition to Jackson’s policies, had to embrace squatterism or perish at the polls. Chapters four and five describe how squatters in the 1830s and 1840s drove the national agenda. The Anglo-Americans who entered Texas and Oregon occupied land outside of U.S. public domain, risking potential conflict with Indigenous communities as well as Mexico and Great Britain. The Polk administration backed these squatters by annexing Texas, claiming Oregon via treaty, and invading Mexico. By 1848, U.S. possessions extended to the Pacific Ocean. Suval cites the acquisition of Oregon Territory and passage of the 1850 Oregon Donation Land Act as the “high water mark of Squatter Democracy” (p. 113). Indeed, in Oregon (and later Kansas), squatters successfully claimed land before the federal government extinguished Indigenous title, a violation of U.S. legal precedent. Yet Oregon’s status as a free territory represented a turning point, as pro-slavery Democrats realized they had created a monster they could no longer control. The book’s final chapters chronicle the dis-integration of the squatter-statesman alliance. While southern elites hoped newly acquired California would legalize slavery, the scores of antislavery squatters who entered the region to claim Mexican land had different plans. Sectional temperatures rose further in 1854 when Stephen A. Douglas proposed popular sovereignty in Kansas, allowing squatters to decide the issue of slavery for themselves at the polls. The result was a violent clash between pro-and anti-slavery forces, triggering a backlash against what detractors [End Page 98] called “squatter sovereignty.” Unable to reach a compromise on slavery in western territories, the Democratic Party soon split along sectional lines and all but guaranteed the election of Abraham Lincoln and southern secession. Dangerous Grounds is an extensively researched, convincingly argued, and readable political history with a fascinating dash of cultural history. Readers of this journal will be particularly interested that Suval makes the U.S. colonization of Oregon a key moment in his narrative. The book might have been strengthened by more robust discussions of property rights and democracy itself. Indeed, Suval’s use of the upper-case Democracy in the title and elsewhere is somewhat confusing. By “Democracy,” Suval does not refer to a system in which the masses...

A cold war text for the COVID generation

A cold war text for the COVID generation

Gettysburg 1963: Civil Rights, Cold War Politics, and Historical Memory in America’s Most Famous Small Town by Jill Ogline Titus

Reviewed by: Gettysburg 1963: Civil Rights, Cold War Politics, and Historical Memory in America’s Most Famous Small Town by Jill Ogline Titus Summer Perritt (bio) Gettysburg 1963: Civil Rights, Cold War Politics, and Historical Memory in America’s Most Famous Small Town. Jill Ogline Titus. Chapel Hill: University of North Carolina Press, 2021. ISBN 978-1-4696-6534-4, 264 pp., paper, $27.95. Jill Ogline Titus’s Gettysburg 1963: Civil Rights, Cold War Politics, and Historical Memory in America’s Most Famous Small Town looks at the evolving memory and meaning of the Battle of Gettysburg during the 1960s Civil War centennial. Titus uses a Cold War framework to understand the battle’s political and cultural uses, arguing that Gettysburg’s “multifaceted identity as an idea, a landscape, and a living community” rendered the small town a useful tool in the fight for and against Black civil rights (2). To craft her narrative, Titus closely reads an impressive array of primary sources such as speeches, newspaper articles, monument dedications, and photographs to demonstrate that historical actors across the board attempted to use the Gettysburg centennial to serve their own contemporary interests. These attempts took the shape of three key narratives: a Lost Cause version of the War that white Southerners used to push back against civil rights agendas, a counter-narrative that suggested the fight for civil rights was the best way to honor the legacy of the Civil War and its fallen heroes, and finally, a Cold War perspective that capitalized on reconciliationist narratives of the War to promote American exceptionalism and democracy abroad. The first part of Titus’s work looks at the historical uses of Gettysburg leading up to the centennial. In the aftermath of the Civil War, tourism quickly became a mainstay for the town, as both white and Black tourists flocked to the site with their own understandings of the battle and its importance in crafting a larger American identity. As the decades passed, however, this understanding quickly became entrenched in contemporary struggles over white supremacy, Black disenfranchisement, and segregation. Beginning in the 1920s, Gettysburg became the key site for Ku Klux Klan activity, and in 1925 it played host to a two-day rally that attracted between twenty and twenty-five thousand attendees. Titus estimates that the Klan’s use of the battlefield [End Page 117] stood as a symbolic gesture intended to reinforce the idea that members of the hate group saw themselves as “modern-day defenders of patriotism and American heritage” and provided a throughline between the battles of the Civil War and what members saw as the ongoing fight for white supremacy (13). In the 1930s, the National Park Service took over management of the battlefield and officially moved Gettysburg into the orbit of Confederate memory, rendering the battle the “High Watermark of the Confederacy” (17). But Titus takes multiple angles into account, examining interpretations of the Gettysburg centennial from the perspective of civil rights workers, politicians, centennial planning-committee members, and local residents, both Black and white. As such, she explores how Black Gettysburgians actively contested white memory of the battle and its contemporary uses. They capitalized on the battlefield’s public status and used it for gatherings, picnics, and exercise. They decorated the graves of Black soldiers on Memorial Day and even refused to participate in commemorative events that portrayed racist reconciliationist narratives of the war. As Titus points out, the years leading up the centennial saw Gettysburg as a contested site where people across the nation came to debate issues of race, citizenship, and belonging. The middle chapters of Gettysburg 1963 explore the pageantry of the centennial and expertly flesh out the varied uses of the battle in a Cold War and civil rights context. A speech made by Pennsylvania governor David Lawrence during the 1961 Memorial Day celebration, for instance, insisted on the Civil War’s importance as a didactic moment in American history, providing a warning to foreign nations that Americans did not shy away from armed conflict when they believed their right to self-determination could be violated. Other politicians and centennial speakers emphasized reconciliation as the major legacy of the Civil War...

Influence of sediment composition on morphology and internal structure of mixed siliciclastic–bioclastic coastal barriers: Contribution of flume experiments

ABSTRACTCoastal barriers are dynamic systems, the morphology and architecture of which are controlled by local hydrodynamics, sea‐level fluctuations at different timescales, geological heritage and sediment composition. Coastal barriers may be composed of siliciclastic sediments, bioclastic sediments, or a mixture of both. Mixed siliciclastic–bioclastic sediments (as common as ‘pure’ sediments) are still little represented in the literature. Changes in sediment composition could affect sedimentary processes which are involved in the construction and stability of coastal barriers due to a different hydrodynamic behaviour between bioclastic and siliciclastic particles. In this study, wave‐flume experiments were used to investigate the role of sediment compositional mixing on the morphology and architecture of coastal barriers. Three different siliciclastic/bioclastic mixtures were exposed to regular wave forcing, together with mean water level fluctuations to create regressive and transgressive depositional units. Compositional mixtures responded similarly in first‐order to mean water‐level fluctuations, with the formation of a bar at low water level. Its subsequent on‐shore migration and reworking as berm deposits during rising water level stages, and with the formation of washover deposits during high water level stages. In detail, the increasing content of bioclastic sediment increased the beachface slope and reduced the length of washover deposits. The faster aggradation of washover sheets with bioclastic‐rich mixtures accelerated the barrier recovery after a submersion and breaching event. A strong segregation between the siliciclastic and the bioclastic grains was observed in the different depositional units, which is attributed both to the coarse size (grain‐size control) and to the flat‐shape (compositional control) of the bioclastic particles.

Increased floodplain inundation in the Amazon since 1980

Extensive floodplains throughout the Amazon basin support important ecosystem services and influence global water and carbon cycles. A recent change in the hydroclimatic regime of the region, with increased rainfall in the northern portions of the basin, has produced record-breaking high water levels on the Amazon River mainstem. Yet, the implications for the magnitude and duration of floodplain inundation across the basin remain unknown. Here we leverage state-of-the-art hydrological models, supported by in-situ and remote sensing observations, to show that the maximum annual inundation extent along the central Amazon increased by 26% since 1980. We further reveal increased flood duration and greater connectivity among open water areas in multiple Amazon floodplain regions. These changes in the hydrological regime of the world’s largest river system have major implications for ecology and biogeochemistry, and require rapid adaptation by vulnerable populations living along Amazonian rivers.

An optimized zonal deformation prediction model for super-high arch dams

The previous zonal deformation prediction models for super-high arch dams focus on the measured deformation law, which cannot capture the trend, periodic and fluctuating characteristics. This greatly limits their physical interpretation and practical applications. To address this issue, this paper proposes an optimized zonal deformation prediction model. First, the variational mode decomposition algorithm is applied to split displacement into trend, periodic and fluctuating components. Representative environmental and load factors are determined by the hierarchical clustering on principal components, and then also decomposed into the trend, low- and high-frequency components according to their physical meanings. Second, an optimized dynamic time warping (DTW) based on shape-based distance is employed to divide the displacement components of measured points into different zones. The centroid sequences are calculated to capture the shared characteristics of the corresponding deformation zones. The zonal data sets of the centroid sequences of displacement components and their strongly related influencing factor components are established. Third, the optimized zonal deformation prediction models using three machine learning algorithms (random forest, least squares support vector machines, and boosted regression tree) and the improved hydrostatic-thermal-time model are constructed. The effectiveness of the optimized model is verified using the measured data collected from the Xiluodu dam. The case study shows that the optimized model can well explain the spatio-temporal characteristics of the trend, periodic and fluctuating displacements. Affected by the geological condition, the radial displacement distribution is not completely symmetrical under high reservoir water level.

Development of a multiphase variable mass flow model and its application in well control for variable gradient managed pressure drilling

A multiphase flow model is an important foundation for well control simulation. In this paper, a multiphase variable mass flow model considering sudden density change was developed for variable gradient managed pressure drilling (MPD) and it was solved by finite difference method (FDM). Further, the model was used to simulate the whole process of well control based on constant bottom-hole pressure for variable gradient MPD. In this way, the advantages of the new gas kick detection method compared with the mud pit increment detection method and the variation laws of key parameters in the whole well control process were investigated. The results indicate that under the condition of small gas rate, the new gas kick detection method is better than the mud pit increment detection method because of its time savings. In the process of gas discharge, the wellbore pressure fluctuates due to the influence of gas expansion, sudden density changes at the separator position and annulus diameter changes at the casing shoe and mud line. The time when the back pressure reaches the maximum lags behind the time when the gas front reaches the wellhead. The mud pit increment increase rate when the gas front reaches the separator position is significantly higher than that in the early stage of gas kick detection.

Avifaunal Diversity and Abundance in the Proposed Sarasalai Mangrove Reserve, Jaffna, Sri Lanka

Mangrove ecosystems are excellent habitats for migrating and resident birds. The proposed Sarasalai mangrove reserve is located in one of the richest waterbird zones in Sri Lanka. This site has never been properly studied as a single site for its avifaunal diversity. Hence, the present study aims to find avifaunal diversity in the Sarasalai mangrove. Data collection was performed from April to December 2021. Eight permanent sampling stations were demarcated along the existing roads and were visited twice a month to collect bird abundance data. A total of 107 bird species belonging to 45 families including 58 waterbird species were recorded in the present study. Bird abundance did not significantly differ among the eight studied sites. Studied sites with the availability of water and good tree cover had the highest Shannon Diversity Index. The mangrove vegetation, with tall grasses, and the high water level were significant factors for bird abundance in some sites. Monthly bird abundance showed a notable increase during the migratory months. Among the recorded bird species, Greater Flamingos showed the highest abundance. Moreover, some rare waterbirds including Indian Spot-billed Duck and Glossy Ibis were commonly recorded. Several putative threats have been recorded during this study, namely unplanned land encroachments, bird hunting, and clearing of mangroves. Although this site has a high value in providing a healthy habitat for many wetland birds, it is yet to be declared a protected area. The lack of a clear boundary and a governing body to protect this area exacerbates its protection issues. Hence, it is proposed that immediate legal actions must be taken to declare this important migratory bird area a mangrove forest reserve.

Effect of pressure on high-temperature oxidation of Ni alloys in supercritical CO2 containing impurities

Direct supercritical CO2 (sCO2) power cycles require structural materials compatible with hot sCO2 containing high levels of water and oxygen impurities. Chromia-forming Ni-based superalloys, which are leading candidates at temperatures > 600 °C, have shown good compatibility in pure sCO2, however potential impurity effects are not well understood. Herein we exposed several commercial Ni-based alloys to 95%CO2-4%H2O-(1−3)%O2 at 750 °C and 0.1 or 20 MPa for 2500 h. Protective chromia scales formed in all cases. Nevertheless, water vapor-assisted oxide volatilization clearly occurred at high pressure. The volatilization rates decreased with time, but still represent a potentially serious compatibility issue in real, high-velocity, sCO2 systems.

Environmental and Nesting Variables Associated with Atlantic Leatherback Sea Turtle (Dermochelys coriacea) Embryonic and Hatching Success Rates in Grenada, West Indies

Annual monitoring of leatherback sea turtle (Dermochelys coriacea) nesting grounds in Grenada, West Indies has identified relatively low hatch rates compared to worldwide trends. This study investigated the impact of selected environmental variables on leatherback sea turtle embryonic development and hatching success rates on Levera Beach in Grenada between 2015-2019. The mean number of nests per year and eggs per nest were 667.6 ± 361.6 and 80.7 ± 23.0 sd, respectively. Within excavated nests, 35.6% ± 22.0 sd of eggs successfully developed embryos and 30.6% ± 22.6 sd of eggs successfully hatched. The number of eggs per nest, along with embryo and hatching success rates, differed by nesting year. Embryo development success rate was associated with nest location, and both embryo development and hatching success rates were positively associated with nest depth and negatively associated with the percentage of eggs exhibiting microbial growth and with the presence of inspissated yolk. There was no embryo development or hatchling success association with month of the nesting season, distance from the high-water mark, distance from vegetation, nor maternal carapace length. The mean nest temperature was 31.7 °C ± 1.64 sd and mean temperatures during the middle third of egg incubation suggest clutches are highly skewed towards a preponderance of female hatchlings. Histopathologic findings in hatchling mortalities included severe, acute, multifocal, heterophilic bronchopneumonia with intralesional bacteria in 4/50 (8%) hatchlings. Data from this study guide conservation strategies by identifying risk factors and further avenues of research needed to support reproductive success of leatherback sea turtles in Grenada and the greater Caribbean region.

Inability of yellow‐bellied toad to accelerate metamorphosis in desiccation conditions

AbstractMany amphibian species inhabit temporary aquatic habitats for reproduction to maximize larval growth under favorable conditions, but accelerate developmental rate to rapidly undergo metamorphosis under stress conditions when high desiccation risk exists. Desiccation affects different aspects of amphibian biology such as developmental rate, body size and mass, and growth rate. We studied the responses of yellow‐bellied toad (Bombina variegata) to different water levels (constant high, decreasing water level, and constant low water level) in the laboratory using individuals collected from natural ponds. To assess the effects of experimental pond drying, we investigated the effects on life‐history and morphological traits at metamorphosis as well as carry‐over effects on post‐metamorphic traits and locomotor performances. We found that B. variegata cannot accelerate developmental rate in response to pond drying. The metamorphs from decreasing and constant low water levels had similar size, mass, growth rate and body condition indices at metamorphosis, and all these traits were lower than in the constant high water level treatment. These changes in life‐history traits at metamorphosis did not affect tail shape although they had carry‐over effects on life‐history and morphological traits after metamorphosis. Post‐metamorphic individuals reared in desiccation treatments had similar but smaller lengths of femur and tibiofibula, but these changes did not have negative consequences on jumping performances. We show that responsiveness to pond drying of B. variegata is probably associated with maximum growth rate in favorable conditions and inability to increase growth rate as well as developmental rate in desiccation conditions. This resulted in prolonged developmental time to reach the minimum size and mass for metamorphosis.

An Experiment in Determining the High-water Mark

As a boundary of the seashore, the high-water mark (HWM) is relevant to the public, the State, and other rights holders in the coastal zone. Unlike most fixed property boundaries that are surveyed and beaconed, the HWM is subject to dynamic natural coastal processes and moves over time. Its location is difficult to determine, and the precision of this determination is unknown. This paper reports on an experiment to measure the precision (variability/repeatability) of the location of the HWM at a variety of sites near Cape Town, by volunteer participants. Four sites were chosen along stable (non-mobile) shores along the open, high energy oceanic shores south of Cape Town on the Cape Peninsula. One of these sites exhibits large variation in coastal terrain and type – at this site three sets of measurements were undertaken, bringing the total number of experimental sites to six. Surveying was undertaken in the South African national control survey system using network real-time kinematic global navigation satellite systems (GNSS).
 This experiment shows that the professional land surveyors located the HWM to ±1,6m, coastal engineers to ±4,1m, and the group of ‘others’ to ±4,2m. The professional land surveyors determined the height of the HWM to ±0,4m over all sites, compared to ±0,7m for all participants. The HWM is likely to be about 4 - 5m above the lowest astronomic tide. However, the line is not a contour – it is affected by weather and local variations in the coastline such as slope and seashore composition. The averaged heights of the HWM at each of the sites for all participants showed a range of 1,3m. Since the boundaries of the seashore cannot be determined with precision, property, cadastral and environmental law needs to continue to respect the nature of this environment and the limitations of locating the HWM.

Revival Mechanism and Prevention Measures of Composite Landslides: A Case Study of the Wenma Expressway Composite Landslide

The resurrection of landslides often occurs in complex strata, where there are often multiple water-resisting zones and weak interlayers. The groundwater level has a significant influence on landslide stability and can lead to the formation of composite landslides and increase the probability of landslide resurrection. In a field investigation of the K39 +400 composite landslide of Wenma Expressway, the deformation characteristics of the landslide surface were obtained by analyzing 34 cracks on the landslide surface. The deep deformation characteristics of the landslide were analyzed by studying the deformation data obtained from deep borehole monitoring. The deformation zone characteristics of landslides were assessed by integrating surface and deep deformation data in the landslide area. The resurrections of shallow landslides in Area I and deep landslides in Area III were due mainly to the long-term high underground water level in the landslide. The stability of the landslide was calculated under various depths of drainage tunnel, and the results showed that the slope was in critical condition when the depth of the drainage tunnel was 15 m; the slope was basically stable when the depth of the drainage tunnel was 20 m and 25 m. When the depth of the drainage tunnel reached more than 30 m, the slope was in a stable state. Groundwater level was found to be the main factor affecting landslide deformation. This case study shows the importance of zoning the deformation characteristics of composite landslides, and the important influence of the groundwater level on landslide resurrection.

Agricultural Pressures on the Quality of Ground and Surface Waters in Catchments of Artificial Reservoirs

Changes in nutrient concentrations in groundwater were investigated to determine the impact of agriculture on water quality in artificial lakes. The study covered three reservoirs in an agricultural area of Wielkopolska (central-western part of Poland). Assessing the agricultural impact required a network of piezometers around the reservoirs, used to determine the degree of groundwater pollution from nutrients supplied to the reservoirs. Moreover, the analysis covered the quality of water in streams flowing into the reservoirs, and in the reservoirs themselves. Field research was conducted every month of the growing season from March to November. The analysis covered land inclination, ground permeability, and soil type. Detailed objectives included: (1) assessment of the agricultural impact on the chemical parameters of ground and surface water quality, and (2) evaluation of the impact of different sources of agricultural pollution on water quality in artificial reservoirs in regards to their management. This study revealed high dynamics of nutrient concentrations, particularly for nitrates and phosphates, in groundwater and surface water. A significant effect of maize cultivation on an increase in nitrate concentrations in the groundwater of the catchment of the Przebędowo Reservoir was evidenced, as well as a substantial effect of the functioning of an animal farm on the quality of groundwaters in the catchment of the Lachotka Reservoir. The nutrient load of agricultural origin in the catchment of the Miedzichowo Reservoir was relatively low. Our study revealed elevated amounts of nutrients such as nitrogen and phosphorus, detected more frequently in groundwater than in running waters, which confirms our hypothesis of the importance of groundwater analysis in detecting the source of pollution of the studied lakes. High nutrient concentrations recorded in groundwater leached from arable fields were also observed in the summer period, failing to confirm the hypothesis that the greatest effect of factors would be related to the spring effect of arable fields on water quality (lack of compact vegetation cover, high water level, etc.). Our study also indicated a greater importance of the type of land use than lithology or permeability of deposits.