Saltwater intrusion is a major hazard to coastal communities as it causes degradation of fresh water resources. The impact of rising sea level on the saltwater intrusion into coastal aquifers has ...been studied for decades, but how human activities affect the extent of saltwater intrusion is poorly understood. Human activities are known to influence groundwater availability indirectly by affecting precipitation patterns and directly by extracting groundwater and reducing recharge. In this paper the authors investigated the integrated impacts of human activities and rising sea level on aquifer recharge in Quintana Roo, Mexico, by incorporating anthropogenic impacts on groundwater recharge into an analytical saltwater intrusion model. The impact of human activities on groundwater extraction was firstly calculated; then, the resulting groundwater recharge was used in a Ghyben–Herzberg analytical model to determine the inland distance of saltwater intrusion. The analytical model tested six scenarios stemming from different combinations of human development patterns, hydrological settings, hydraulic conditions and rising sea level to obtain the range of possible inland movement of saltwater intrusion. Our results indicate that the groundwater recharge will decrease to 32.6 mm year
−1
if human activities increase by 50 % more. With 1-m sea level rise, inland saltwater intrusion distance is estimated to be up to 150 and 1 km under head-controlled and flux-controlled scenarios, respectively. A sensitivity analysis of the model reveals that the large hydraulic conductivity of the Quintana Roo aquifer (0.26–68.8 m s
−1
) is the most important factor in determining saltwater intrusion distance. Therefore, in this aquifer, the response to human activities is greatly exceeded by natural hydrogeological conditions.
A model was used to study the evolution of cohesive clay coasts under different environmental and geological conditions, and the effect of future climate change. The model considered wave impact on ...the bluff and in the intertidal zone, and bottom generated shear stresses and the protective and abrasive action of beach sediment in the intertidal and subtidal zones. Quasi-equilibrium conditions developed in model runs, with parallel slope retreat in the upper portion of the profiles, and slope decline in the lower portions. Profile gradient below the low tidal level increased with the threshold shear stress for bottom erosion. Therefore, rates of wave attenuation were lower in resistant than in weak materials, and the intertidal zones were wider and more gently sloping. The widest and gentlest intertidal zones developed in runs that had no sediment. The largest waves played little role in platform development, in part because of low frequency but mainly because they expend most of their energy in crossing wide, turbulent surf zones. The model suggested that rising sea level will usually result in accelerated rates of bluff recession, especially if the rise is rapid. Simultaneous increases in the frequency of moderately large waves, as opposed to the largest waves, may also generate marked increases in erosion on bluffs and in intertidal and supratidal zones, although erosion may be reduced at some elevations where there is beach sediment. Positive or negative changes in beach volume can increase or decrease rates of bluff erosion.
Predictions of future requirements for the protection of maritime archaeological sites are made using the fetch method which has been developed to evaluate the quality of landing-places and navigable ...channels. The very useful method may explain why archaeological sites along the coast are rare in some areas, but numerous in others. Many of them are vulnerable to destruction by the effects of climate change, especially rising sea-levels, based on the IPCC scenarios. The objective fetch method can be used worldwide to predict where new finds of sites close to sea-level can be expected, and also to predict a site's vulnerability.
Approaches to the modelling of long-term, large-scale (1–100 year and drainage basin to coastal zone) behaviour are outlined for the catchments of the Humber and Tamar estuaries, UK, and San ...Francisco Bay, USA. The estuarine environment is particularly difficult to model. Once fluvial materials enter an estuary, sharp chemical gradients and complex physical and biochemical dynamics can result in large changes to the amount, chemical nature and timing of the flux of nutrients and other materials that are transported to the coastal zone. Examples are given both of catchment models for the three systems and of an estuarine model that has been used to estimate contemporary fluxes of some nitrogen species from the Humber catchment to the North Sea, in an attempt to forecast the possible effects associated with climate change. Other applications of long-term models are discussed, including predictions of oxygen isotope ratio distributions in San Francisco Bay, which are of value to palaeo studies, and the dependence of salt intrusion on rising sea level and drought conditions there. Some of the more difficult modelling problems involve the determination of estuarine sediment transport and its consequences. A problem which has received little attention up to now, but which is becoming a very active area of research, is the influence of biota on sediment transport. Long-term modelling of fine sediment transport and its application to contaminant (including radionuclide) transport and dispersion to the coastal zone are discussed for the Tamar Estuary. Other long-term estuarine problems that are discussed include the modelling of seasonal heat fluxes from the Tamar to its coastal zone, and the dispersion of tracers within the coastal zone using three-dimensional simulations of heat, salinity and flow. The article is mainly concerned with simulations that require only reasonably short amounts of time to run on a PC and with models that are not intended to give solutions of great temporal or spatial resolution. Generally, they are intended to provide insights into phenomena and systems. To achieve this, a common feature of the long-term models has been their parameterisation of some intratidal processes, such as sediment resuspension and deposition, or tidal mixing. Provided the parameterisations are physically based and lead to good comparisons with available data, when these exist, then the approach would appear to be a valid ‘use’ rather than an invalid ‘abuse’ of models.
A multidisciplinary study has been carried out on a 51 m long core, drilled on coastal lowlands near the Albegna River (Tuscany, Central Italy). Both sedimentological and faunal analyses (ostracods ...and molluscs) indicate a coastal lagoon environment repeatedly influenced both by the rising Holocene sea and the Albegna River alluvial inflow. δ
13C, δ
18O, Mg/Ca, Sr/Ca and
87Sr/
86Sr analyses were performed on
Cyprideis torosa shells in order to detail the influence of Albegna River freshwater on the coastal lagoon water. The analytical data illustrate the difficulties of using geochemical proxies in marginal marine settings. Four radiocarbon dates provide a chronostratigraphy for the early Holocene part of the core. The data are used to reconstruct Late Pleistocene to early Holocene palaeoenvironments along this part of the coast and show the development of freshwater environments followed by a coastal brackish lagoon formed in response to the initial Holocene rapid rise in relative sea level. An attempt is made to relate sediments and age data from the core to the relative sea-level curve for the Tyrrhenian Sea.
The physical disappearance of a state's entire territory is an event forecasted to happen as a result of sea-level rise, affecting some of the smallest nation states in the world, primarily islands ...in the South Pacific. The focus of this article is on the human rights of the inhabitants of the disappearing states when they are forced to relocate.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NMLJ, NUK, ODKLJ, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
A survey of soils and trees was conducted on Syunkunitai coastal sand dune in eastern Hokkaido to clarify the relationships between the soil properties and the plant cover type. A belt transect of ...360 m in length was established across the dune. Three community types, that is, a Picea glehnii forest, an Abies sachalinensis forest, and a salt marsh were recognized. Soil types at the study area were determined to be sandy immature soil and peat soil. Their horizon sequences were described as A0–V–C or T–V–C layers (A0, T, V, and C indicate layers of leaf litter, peat, volcanic deposit, and parent material, respectively). The Abies sachalinensis forest was characterized by a relatively high calcium concentration in the surface soil layer and a tendency for podzolization in the volcanic deposit layer. The Picea glehnii forest was characterized by peat accumulation because of the high ground water table, volcanic deposits in the soil profile, and the strong influence of sea salt on the soil chemistry. The roots in the Picea glehnii forest were distributed more shallowly than those in the Abies sachalinensis forest, thus avoiding the high water table level as well as the influence of seawater in the soil. The salt marsh showed an extremely high sodium concentration and base saturation, indicating that this area was directly affected by seawater. Recently, the periphery of the Picea glehnii forest on Syunkunitai sand dune has been declining because of seawater inundation caused by ground subsidence.
In a Virginia (USA) marsh undergoing transgression due to rising sea level, we examined the stability of the boundary between nearly monotypic patches of Juncus roemerianus and adjacent plant ...communities for 6 years. Patch stability was evaluated by examining interannual changes in 5 cover classes: J. roemerianus, Spartina alterniflora, S. patens, Distichlis spicata, and wrack. Patches were chosen at four sites ranging from a low marsh site with mineral soil that receives semidiurnal estuarine flooding to a high marsh site with organic rich soil that receives only storm-induced flooding from the estuary. The semidiurnally flooded site in the low marsh was the only one losing J. roemerianus cover and had largest interannual variations in wrack and bare soil. At a high marsh site near a tidal creek, incidence of wrack cover was high and patchy but apparently insufficient to reduce cover of J. roemerianus. At the two sites with infrequent estuarine flooding because of distance from tidal creeks, wrack was virtually absent and patches of J. roemerianus expanded. Patch expansion at one of these sites occurred even though the marsh subsided, and coverage by the three other species decreased over the course of the study. Overall, J. roemerianus patches appeared quite stable, with declines associated with wrack disturbance at the site that had the deepest and most frequent tidal flooding. Patch stability is due in part to the wide tolerance of J. roemerianus for hydroperiod and salinity.
L’érosion des plages est un phénomène général dans le monde. Elle est essentiellement due à une pénurie en sable et en galets sur les côtes. Cette pénurie, qui a commencé à se manifester après la fin ...de la transgression postglaciaire, a été accentuée à l’époque contemporaine par des actions humaines, en particulier la construction de barrages sur les fleuves. L’élévation attendue du niveau de la mer aggravera probablement l’érosion des plages.
Beach erosion, a world-wide phenomenon, is mainly caused by a shortage of sand and shingle on coasts. This shortage, which began after the culmination of the postglacial transgression, has worsened in recent times as a result of human activity, particularly the construction of dams on rivers. The expected rise in the sea level is likely to further exacerbate beach erosion.
La erosión playera es un fenómeno general en el mundo. Se debe esencialmente a un déficit en arena y cantos en las costas. Este déficit empezó a manifestarse después del fin de la última transgresión postglaciar y se desarrolla en la época actual por las acciones humanas, particularmente con el represamiento de los ríos. La subida esperada del nivel del mar tendra seguramente que accentuar la erosión playera.
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