Assessment Of Shoreline Changes Research Articles

Assessment of Shoreline Changes and Evaluation of Coastal Protection Methods to Mitigate Erosion

In this paper, the combined use of satellite images and morphodynamic models is applied to assess the coastline changes of an erosion-prone deltaic zone in Northern Greece (Nestos River delta). Satellite images over the last 31 years were used to estimate the erosion rates at the eastern, central and western parts of the delta. The numerical model LITPACK, coupled with wave and hydrodynamic nearshore models, was calibrated based on these results, and was further utilized to predict the shoreline evolution with and without “hard” protection works. Results show that the model underestimated erosion rates over all studied sub-sections, but showed fair agreement to remote sensing analysis when focusing on the zones of major erosion. “Hard” coastal protection structures were tested to assess their mitigation efficiency in terms of longshore and cross-shore sediment transport reduction. LITPACK considered that the scenario of seven rubble-mound breakwaters with low seaward and lee-side slopes, positioned between 9 m and 19 m depicted the best results, even reversing coastline retreat process.

A Comparison of Shoreline Changes Estimated Using the Base of Beach and Edge of Vegetation Line at North Keeling Island.

ABSTRACT Adnan, F.A.F.; Hamylton, S.M., and Woodroffe, C.D., 2016. A Comparison of Shoreline Changes Estimated Using the Base of Beach and Edge of Vegetation Line at North Keeling Island. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 967 - 971. Coconut Creek (Florida), ISSN 0749-0208. The vulnerability of reef islands is often assessed by measuring changes in shoreline positions over time. Historical aerial photographs provide valuable information of past shoreline dynamics and are commonly incorporated in shoreline change assessment. Edge of vegetation line is the most common shoreline proxy adopted for assessments of reef island change because it is a visually distinguishable feature in aerial photographs, when compared to other coastal features such as high water line and base of beach. This study assesses shoreline changes of North Keeling I...

Évaluation de l’évolution du trait de côte et du bilan sédimentaire littoral en baie de Wissant (nord de la France) par LiDAR aéroporté

Des leves topographiques du littoral de la baie de Wissant realises par LiDAR aeroporte entre 2008 et 2014 ont ete utilises pour analyser les variations de la position du trait de cote et les variations des volumes sedimentaires dans les dunes cotieres et sur la plage. Cette periode de mesure a ete marquee par une succession de tempetes fin 2013 et debut 2014 lors desquelles de hauts niveaux d’eau avec des periodes de retour superieurs a 10 ans ont entraine une erosion importante des dunes cotieres. Bien que le trait de cote ait recule de plus de 20 m a plusieurs endroits entre 2008 et 2014, certains secteurs ont ete caracterises par une stabilite de la ligne de rivage ou ont meme pu connaitre une legere avancee du trait de cote en raison d’un developpement de dunes cotieres vers le large. La comparaison entre l’evolution du trait de cote et le volume initial du haut de plage en 2008 a montre que les reculs les plus importants se sont essentiellement produits dans les secteurs ou l’on pouvait observer une absence de haut de plage a maree haute. Nos resultats suggerent egalement qu’a partir d’un volume de sediments d’environ 12 m3 m-1 sur le haut de plage (i.e., au-dessus du niveau des pleines mers moyennes), le trait de cote est stable ou montre une tendance a la progradation vers le large, meme lorsque des tempetes associees a des hauts niveaux d’eau de periodes de retour superieures a 10 ans se produisent. La mise en evidence d’un tel seuil en termes de volume de sediment sur le haut de plage pourrait constituer une aide significative pour une meilleure gestion de l’evolution du trait de cote en fournissant une estimation des volumes minimum de sable necessaires pour assurer une stabilite de la ligne de rivage.

Shoreline change assessment for various types of coasts using multi-temporal Landsat imagery of the east coast of South Korea

ABSTRACTShoreline change assessment is an important task for protecting coastal properties and preserving coastal environments. This research aimed to assess the shoreline changes using the multi-temporal Landsat imagery, acquired from the east coast of South Korea during 1994 and 2014. The procedure for the shoreline change assessment consists of the following steps: (i) generating the normalized difference water index (NDWI) map from each Landsat image; (ii) extracting the shorelines from each NDWI map through the thresholding method; and (iii) assessing the shoreline changes in the various types of coasts such as the sandy, rocky and harbour coasts using the checkpoints with 1 km intervals. The statistical results showed that 94% of the shorelines in the sandy coasts and 96% of the shorelines in the rocky coasts moved landward between 1994 and 2014 due to coastal erosions, while 91% of the shorelines in the harbour coasts moved seaward during the same period due to the land reclamation works. This research contributed to the assessment of the shoreline changes and the calculation of the erosion rates in the various coasts of the study area between 1994 and 2014.

Comparison of Shoreline Change Rates along the South Atlantic Bight and Northern Gulf of Mexico Coasts for Better Evaluation of Future Shoreline Positions under Sea Level Rise

ABSTRACT Passeri, D.L.; Hagen, S.C.; and Irish, J.L., 2014. Comparison of shoreline change rates along the South Atlantic Bight and Northern Gulf of Mexico coasts for better evaluation of future shoreline positions under sea level rise. Shoreline change rates established by the USGS Coastal Vulnerability Index (CVI) (Thieler and Hammar-Klose, 1999; Thieler and Hammar-Klose, 2000), the USGS National Assessment of Shoreline Change (Morton et al., 2004; Morton and Miller, 2005) and erosion rates estimated using the Bruun Rule (Bruun, 1962) are compared along sandy shorelines of the U.S. South Atlantic Bight and Northern Gulf of Mexico coasts. The intent of the study is not to regard one method better than another, but rather to explore similarities and differences between the methods. Based on the comparison, the following recommendations are offered for quantifying future shoreline positions under sea level rise(SLR). In areas where long-term erosion rates correspond well with rates predicted by the Bruun R...

Shoreline change assessment using remote sensing and GIS techniques: a case study of the Medjerda delta coast, Tunisia

Eight scenes of Landsat Multispectral Scanner, Thematic Mapper, Enhanced Thematic Mapper Plus, and Operational Land Imager sensors, covering the period between 1972 and 2013, were used to demarcate shoreline positions and estimate shoreline change rates of the Medjerda delta coast, northeastern Tunisia. The method relies on image processing techniques using the IDRISI software, and the Digital Shoreline Analysis System, a free extension for ArcGIS software, which provides a set of tools permitting transects-based calculation of shoreline displacement. First, the Landsat images were radiometrically and geometrically corrected. Second, band ratioing, reclassification, raster to vector conversion, and smoothing techniques are applied successively to detect and extract the multi-temporal shoreline data. Third, these data are overlaid and the changes are calculated using the end points and linear regression methods. The results indicate significant shoreline changes ranging from 8.6 to −42.6 m/year, while some parts remained unchanged. The estimated shoreline change rates are comparable with those obtained through in situ measurements and from the analysis of multi-date aerial photos and toposheets. The main causes of erosion in particular are related to the natural shifting of the Medjerda River course and mouth, damming of Medjerda and its tributaries, construction of Ghar El Melh port, and the destruction of the small bordering dunes in addition to the wave-induced longshore currents, relative sea level rise due mainly to accelerated coastal subsidence, and sand mining.

A Summary of Historical Shoreline Changes on Beaches of Kauai, Oahu, and Maui, Hawaii

ABSTRACT Romine, B.M. and Fletcher, C.H., 2013. A summary of historical shoreline changes on beaches of Kauai, Oahu, and Maui, Hawaii. Shoreline change was measured along the beaches of Kauai, Oahu, and Maui (Hawaii) using historical shorelines digitized from aerial photographs and survey charts for the U.S. Geological Survey's National Assessment of Shoreline Change. To our knowledge, this is the most comprehensive report on shoreline change throughout Hawaii and supplements the limited data on beach changes in carbonate reef–dominated systems. Trends in long-term (early 1900s–present) and short-term (mid-1940s–present) shoreline change were calculated at regular intervals (20 m) along the shore using weighted linear regression. Erosion dominated the shoreline change in Hawaii, with 70% of beaches being erosional (long-term), including 9% (21 km) that was completely lost to erosion (e.g., seawalls), and an average shoreline change rate of −0.11 ± 0.01 m/y. Short-term results were somewhat less erosional ...

Shoreline changes interpreted from multi-temporal aerial photographs and high resolution satellite images: Wotje Atoll, Marshall Islands

Wotje Atoll is located at 9°25′N and 170°04′E within the Republic of the Marshall Islands in the central Pacific Ocean. As on other atolls, the islands perched along the rim of Wotje are low-lying and considered highly vulnerable to the impacts of climate change. A widely anticipated impact of continued sea level rise is the chronic erosion of island shorelines. Using a combination of aerial photographs and satellite imagery shoreline changes are assessed over a 67-year period characterized by rising sea level. Results indicate that between 1945 and 2010 shoreline accretion is more prevalent than erosion, with an average Net Shoreline Movement (NSM) of +1.74m, indicating accretion. Shorelines were accretionary along the lagoon, ocean and channel facing shorelines, as well as on elongate spits and small islands. A high-frequency assessment of shoreline change on a subset of islands in the east of Wotje reveals that islands were stable, with a balance between shoreline accretion and erosion. Shorelines interpreted from high resolution satellite imagery captured between 2004 and 2012 indicate that shorelines within this sample of islands are largely in an erosive state. The post-2004 shift toward erosion may be sea level rise induced, or part of an unresolved shoreline oscillation. This study demonstrates the critical need for improved shoreline change monitoring within atoll settings in order to assess sea level rise impacts along island shorelines.

Assessment of shoreline changes along the Lithuanian Baltic Sea coast during the period 1947–2010

Shoreline position measurements at various time instants can be used to derive quantitative estimates of the rate of shoreline change and help to understand the magnitude and timing of erosion or accretion processes. Aerial photographs and topographic maps from 1947 to 2010 have been used to derive instantaneous shoreline positions, from which shoreline change rates have been estimated using statistical parameters: shoreline change envelope (SCE), net shoreline movement (NSM), and end-point rate (EPR). Non-metric multi-dimensional scaling (nMDS) has been applied for shoreline classification into dynamic sectors. This study was carried out along 90.6 km of Lithuanian Baltic Sea coast over the time span 1947 to 2010. The study demonstrated that combined use of cartographic data and statistical methods could be a reliable method for shoreline related studies. Application of such data seems to be trustworthy in qualitative monitoring of shoreline changes, while it is the only available method for long term studies.

ASSESSING SHORELINE CHANGE USING SATELLITE-DERIVED SHORELINES IN PROGRESO, YUCATÁN, MÉXICO

Assessment of shoreline change during a six-year period using Satellite-Derived Shorelines (SDS) was carried out in Progreso, Yucatán, México. Confidence bounds for the SDS were defined based on the deviation between quasi-simultaneous in situ shoreline measurements and SDS. The main objective of this paper is to show that optical satellite images are a valuable resource to study shoreline change covering large geographical scales (>10km), as well as short (5 years) temporal scales. This approach can be particularly useful for those areas with a lack of shoreline records. The results presented here show that detection of differences between seasons and years is achievable using SDS. Furthermore, rates of change are also possible to assess.

Error determination in the photogrammetric assessment of shoreline changes

The evaluation of error or uncertainty in shoreline change studies is an issue of prime importance for providing an adequate framework for calculated rates of change and to allow the establishment of threshold values above which the rates would be significant. In this note, a practical, easy-to-use method is presented to estimate error involved in the calculation of shoreline changes on aerial photographs, including the three most used types of shoreline indicators: high water line, dune/cliff toe and cliff top. This approach takes into account the specific characteristics of each shoreline proxy, such as relief in the case of the cliff top or tidal oscillations in the case of the high water line. At the same time it includes the error components that are independent from the proxy, basically related to the technical aspects of the process such as photo scanning and georeferencing. A practical example of application of the method is provided for several types of data inputs, based on shoreline changes around the Bay of Cádiz (SW Spain).

Assessment of shoreline changes in the western side of Zanzibar channel using satellite remote sensing

The present study uses a satellite remote sensing approach for assessing coastal sediment dynamics in the western side of the Zanzibar channel, Tanzania. Four Landsat images (1986, 1998, 1999 and 2000) were used for the study. Investigation of the four images revealed that the Ruvu delta north of the river mouth has been growing rapidly, especially between 1986 and 1998, with an annual northward linear growth rate of about 133 m year−1 and an annual areal growth rate of about 1 km2 every 3 years. The study identified a palaeo-shoreline feature that is parallel to the present shoreline and located about 1.9 km inland from the present shoreline. An important sediment contributor to river Ruvu is derived from the Uluguru Mountains, a tropical mountainous area located about 200 km from the coastline of the Tanzania mainland. The working hypothesis is that either the observed growth of the delta occurred at a gradual rate between 1986 and 1998 or it was mainly an episodic event related to the extreme rainfall events such as the 1997/98 El Niño–Southern Oscillation (ENSO) event, which was associated with extreme rainfall and widespread landslides.