Coastal Erosion Problems Research Articles

Coastal retreat in the plain of Marathon (East Attica), Greece: cause and effects

The drainage network of Inois River is located in East Attica. The river has formed a deltaic fan on which two main distributories are observed: the older western channel (Sehri Rema) and the younger castern one (Kenourio Rema). The purpose of this paper is to study the recent evolution of Inois River on its deltaic fan, the changes that have taken place and the problems that have been created in property loss in the coastal environment near the mouth of Inois River in the last decades. The construction of Marathon dam in the 1920's resulted in a retreat of the coastline near the mouth of Kenourio Rema and this process is still going on today. The dam prevents the transportation and deposition of sediments to the lower reaches of the drainage system of Inois River and results in the silting up of the artificial lake of Marathon. Following comparative observations of aiгphotos of various years (1938-1988) а retreat of the coastline of the order of I m/year is observed in this area. The loss of land has created great concern to property owners who have appealed to local administrative bodies to no avail. Various crude defensive structures constructed from time to time provide no solution to the problem of coastal erosion. If the anticipated rapid sea-level rise of the near future is confirmed, then the retreat of the coastline in this area is expected to accelerate in the coming decades and create even more serious problems to the coastal environment.

Beach nourishment, philosophy and coastal protection policy

Like many other structures (e.g. bridges, buildings), some coasts need maintenance. Regular maintenance of structures is never considered as a waste of money, but rather as conservation of valuable investments. The repetition of beach nourishment is often seen as a negative aspect. In this respect the attitude of some coastal zone managers should change, since beach nourishment is a very versatile tool in mitigating coastal erosion problems. For the design of coastal defense schemes distinction can be made between curing the disease and treating the symptons, beach nourishment often being an example of the latter. A philosophy is given concerning the nourishment of sand at the offshore zone, the waterline, the dry beach, the dune front, and the top and the backside of the dune. It is recommended to define a set-back line sufficiently landward, and to provide the corresponding legal tools in order to allow the coastal zone manager space and time to execute his coastal defense policy.

Preliminary assessments of the occurrence and effects of utilization of sand and aggregate resources of the Louisiana inner shelf

Louisiana is experiencing the most critical coastal erosion and land loss problem in the United States. Shoreline erosion rates exceed 6 m/yr in more than 80% of the Louisiana coastal zone and can be up to 50 m/yr in areas impacted by hurricanes. The barrier islands have decreased in area by some 40% since 1880. Land loss from coastal marshlands and ridgelands from both natural and human-induced processes is estimated to exceed 100 km 2/yr. In response, a two-phase plan has been established, calling for barrier-island restoration and beach nourishment, both requiring large amounts of sand. The plan will be cost-effective only if sand can be found offshore in sufficient quantities close to project sites. To locate such deposits, the Louisiana Geological Survey is conducting an inventory of nearshore sand resources on the Louisiana continental shelf. Exploration for offshore sand deposits is conducted in two phases, with high-resolution seismic reflection profiling to locate potential sand bodies followed by vibracoring to confirm seismic intepretations and obtain samples for textural characterization. As part of the initial stages of the program, reconnaissance high-resolution seismic investigations of three areas of the continental shelf representing different stages in the evolutionary sequence of barrier shorelines were carried out. The Timbalier Islands, flanking barriers of the eroding Caminada-Moreau headland, contain potential sand resources associated with buried tidal and distributary channels. The Chandeleur Islands, a barrier-island arc, have potential offshore sands in the form of truncated spit and tidal inlet deposits, submerged beach ridges, and distributary channels. Trinity Shoal, an inner shelf shoal, is an offshore feature containing up to 2 × 10 9 m 3 of material, most of which is probably fine sand. These reconnaissance surveys have demonstrated the occurrence of sand resources on the Louisiana continental shelf. Utilization of such deposits for island restoration or beach nourishment raises the question of potential adverse effects on the shoreline due to alteration of the inner shelf bathymetry by removing material or deposition of spoil in the process of dredging. Wave refraction analysis models provide a means by which hypothetical wave energy distribution can be determined and possible changes due to resource utilization assessed. A preliminary assessment of the consequences of using sand from Ship Shoal, a large shore-parallel feature, as borrow material for beach nourishment was conducted. Initial results indicate that the shoal serves to attenuate storm waves, and removal of this feature would result in increased erosion and overwash on the adjacent Isles Dernieres barrier-island shoreline. These findings illustrate the need to determine optimum dredging configurations if environmentally deleterious effects of utilization of offshore and aggregate resources are to be minimized.

Geology of Port Elizabeth, Republic of South Africa

Research Article| November 01, 1987 Geology of Port Elizabeth, Republic of South Africa NEAL G. CARTER NEAL G. CARTER Hill Kaplan Scott Incorporated, P.O. Box 3965, Cape Town 8000, Republic of South Africa Search for other works by this author on: GSW Google Scholar Environmental & Engineering Geoscience (1987) xxiv (4): 441–467. https://doi.org/10.2113/gseegeosci.xxiv.4.441 Article history first online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation NEAL G. CARTER; Geology of Port Elizabeth, Republic of South Africa. Environmental & Engineering Geoscience 1987;; xxiv (4): 441–467. doi: https://doi.org/10.2113/gseegeosci.xxiv.4.441 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyEnvironmental & Engineering Geoscience Search Advanced Search Abstract The major portion of the Port Elizabeth municipal area is underlain by rocks of the Table Mountain Group, Cretaceous strata, Recent estuarine and alluvial sediments and semi-consolidated sands. The Alexandra Limestone Formation, raised beach deposits, and dune sands underlie the remainder of the area.The most significant geotechnical characteristics of the different geological formations are the heaving clays and slope instability problems associated with the Cretaceous strata. Large supplies of construction materials are available. They include sand and gravel which are obtained from the alluvium, crushed stone from the quartzites of the Table Mountain Group, and brick clays from the Cretaceous strata. Salt is produced on a large scale in the Swartkops River valley.Other noteworthy features in the area include surface and artesian water supplies for Port Elizabeth and the surrounding areas, flooding in the various river valleys, particularly the Swartkops, the coastal and river erosion problems, sewage and solid waste disposal. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Protective works and geological conservation

Abstract Britain’s rich heritage of internationally important geological sites is well known to engineers and geologists alike, but from time to time, the undertaking of protective works on unstable slopes or cliffs designated as Sites of Special Scientific Interest bring conservationists and engineers into conflict. Many classic geological localities occur along the coastline of Britain, such as the Jurassic sequences of Dorset, the glacial and interglacial sediments of the North Norfolk Coast and the stratotypes of the Hampshire Basin. Unfortunately, many of these coastlines are inherently unstable, suffering rates of erosion of up to 2–3 m per annum. Where such cliffs occur in close proximity to areas of habitation or recreation, there is strong local pressure to find an engineered solution to the problem of coastal erosion. Traditionally, such schemes involve the construction of concrete sea walls, cliff grading and cliff drainage, leading in some instances to the obliteration of any geological interest which may formerly have existed. The Nature Conservancy Council has a direct responsibility to monitor developments which may have an effect on all SSSIs and is automatically consulted in the event of an application being made by an individual or local authority to undertake coast protection works. It must be said that only a small proportion of the total number of applications made are considered to be damaging to the network of SSSIs and in those instances, an attempt is made to negotiate a compromise which allows for the coast to be protected from further erosion, whilst safeguarding the scientific interest. Case histories are given to illustrate the range of problems which are posed by engineering works and the way in which apparent conflict of interests may be resolved.

An approach to the problem of coastal erosion in quaternary sediments

Approximately 40 per cent of the shorelines of the lower Great Lakes are backed by relatively weak Quaternary sediments, and similar shorelines are found on many middle and high-latitude coasts. The high rates of bluff recession which are characteristic of these areas lead to economic losses through erosion of land and damage to buildings, and may prompt a wide range of measures designed to reduce erosion and protect property. Assessment of the physical problem and of possible solutions to it can best be achieved through a sediment budget approach. This is illustrated through a case study of an area near Grimsby, Ontario. The volume of sediment supply to the beach was calculated from measurements of bluff height and annual recession rates. The potential volume of longshore sediment transport was determined from the wave climate of the area and computer modelling of wave refraction. The relationship between sediment supply and potential transport rate can be used to assess the magnitude of the sediment deficit or surplus at points along the shoreline, and this provides an insight into the controls on alongshore variations in recession rates.