­­DEVELOPMENT OF A TERRESTRIAL PROXY FOR PALEO SEA-LEVEL USING LITHIFIED COASTAL-DUNE MORPHOLOGY

2020 ◽  
Author(s):  
Kat Wilson ◽  
◽  
David Mohrig ◽  
Benjamin Rendall
Keyword(s):  
Sea Level ◽  
Coastal Dune ◽  
Dune Morphology

Geomophological and vulnerability analysis of a coastal delta under increased hydrological alteration over the past two centuries: Tana River delta, Kenya, East Africa.

2021 ◽  
Author(s):  
Peter Gitau ◽  
Stéphanie Duvail ◽  
Dirk Verschuren ◽  
Dominique Guillaud
Keyword(s):  
Sea Level Rise ◽  
East Africa ◽  
Sea Level ◽  
Coastal Dune ◽  
River Delta ◽  
River Channels ◽  
Dune System ◽  
The Past ◽  
Tana River ◽  
Coastal Dune System

<p>Coastal deltas worldwide are under risk of degradation due to the increasing impacts of sea-level rise, and continuous human alterations of river basin hydrology. This research highlights the geomorphological changes that have occurred within the Tana River delta in Kenya, an important deltaic ecosystem of high biodiversity value in East Africa.</p><p>The geomorphological features (river channels, floodplain, coastal dune system) and their evolution over the past two centuries were described. Aerial and satellite imagery was used to assess the magnitude and distribution of coastal changes from the 1960s to present.  Additionally, sediment cores recovered within the mangrove environment were analysed to establish the succession of sedimentation periods and patterns. Finally, we explored the response of the coastal processes of deposition and erosion under anthropogenic alterations of the hydrological system.</p><p>It was established that over the past two centuries Tana River has changed its main channel and outlet to the Indian Ocean on three occasions. A first river avulsion occurred in the 1860s, followed by a second avulsion in the late 1890s that was promoted by human interference through channel expansion and dyke construction. The third change in river course has occurred gradually over the past 20 years, amid human efforts to engineer the river channels.</p><p>From the sediment analysis and radiocarbon dating, it is ascertained that the lower deltaic region developed rapidly over the past ~180 years, facilitated by increased sedimentation from the main Tana River. On the other hand, analysis of the coastline changes indicate that there has been increased erosion of the coastal dune system and mangrove vegetation along the former river outlet, leading to rapid marine intrusion into local subsistence farming areas. By analysing the combined impacts of both natural river dynamics and human alteration we highlight how the integrity of the Tana River delta has increasingly become vulnerable under present sea level rise and continued upstream river alteration.</p>

scholarly journals OSL-SAR dating of sediments from Brazilian aeolian system: Dama Branca, Rio de Janeiro, morphodynamic study

2019 ◽  
Vol 7 (2A) ◽  
Author(s):  
Lucas Sátiro Do Carmo
Keyword(s):  
Sea Level ◽  
Rio De Janeiro ◽  
Climatic Changes ◽  
Coastal Dune ◽  
Optically Stimulated Luminescence ◽  
Relative Sea Level ◽  
Dune Field ◽  
Wind Action ◽  
Aeolian Systems ◽  
The Town

It has been reported that the formation and stabilization of coastal dune fields in Brazil have a dependence on the climatic changes, Relative Sea Level (RSL) variations, etc. In this work, a dune field known as “Dama Branca”, located in the town of Cabo Frio, Rio de Janeiro, has been studied to understand its mobility, formation and stabilization. Dating by trapped charge dating techniques as Optically Stimulated Luminescence (OSL) using the Single Aliquot Regenerative protocol (SAR), helps us to understand the formation and dynamics of aeolian systems in Brazil. Samples from two positions; DB and 2DB, were collected from different heights and points for dating. The results obtained by OSL-SAR showed that ages decrease as the height from the dune base increase and older samples are found in deeper horizontal positions. The ages from the base of the studied dunes indicated that its stabilization occurred during the recess of the sea level and that erosion caused by the wind action is revealing an old generation of this dune filed.

scholarly journals The temporal and spatial variability of coastal dune erosion in the Polish Baltic coastal zone

Baltica ◽  
2018 ◽  
Vol 30 (2) ◽  
pp. 106-97 ◽  
Author(s):  
Jacek Tylkowski
Keyword(s):  
Spatial Variability ◽  
Sea Level ◽  
Atmospheric Circulation ◽  
Coastal Zone ◽  
Storm Surges ◽  
Coastal Dunes ◽  
Coastal Dune ◽  
Dune Erosion ◽  
Temporal And Spatial Variability ◽  
Temporal And Spatial

The study looked at the temporal and spatial variability of dune erosion in the Polish Baltic coastal zone in the period 1972–2008. The dynamics of coastal dune erosion in the area are presented in relationship to the main hydro-meteorological factors: storm surges and types of atmospheric circulation. The greatest destruction of the coastal dunes in Poland was observed on sandbar sections, where the erosion was over 100,000 m3 per 1 km, causing dune baseline retreat by several tens of meters. The main causes of this considerable coastal erosion are the sudden rise of the sea level and the waves during extreme storm surges, when the loss of dune sediment across the entire Polish Baltic Sea coastal zone can reach about 400,000 m3. These extremely erosive storm surges are particularly generated by cyclonic atmospheric circulation, which accounts for more than 52% of such surges from the north-west, north, and west. It was also found that sea level increases of more than 1 meter (about 602 cm) above the mean sea level (about 500 cm) can result in significant erosion of coastal dunes in Poland (>100,000 m3). However, there is a relationship between the intensity of the dune erosion and sea level. The results of the present study could be applied to studies of Baltic coastal dunes functioning in the lagoon-spit coastline, especially in the stretch from Estonia to Germany.

Climatic and sea level controls on Late Quaternary eolian activity on the Agulhas Plain, South Africa

2006 ◽  
Vol 65 (02) ◽  
pp. 252-263 ◽  
Author(s):  
Andrew S. Carr ◽  
David S.G. Thomas ◽  
Mark D. Bateman
Keyword(s):  
Sea Level ◽  
Late Quaternary ◽  
Coastal Dunes ◽  
Coastal Dune ◽  
Published Data ◽  
Fluvial Systems ◽  
Groundwater Levels ◽  
Rainfall Seasonality ◽  
The Individual ◽  
Induced Changes

AbstractLocated at the interface between the temperate westerly and sub-tropical climate systems, South Africa's winter rainfall zone (WRZ) is a key location in understanding Late Quaternary atmospheric circulation dynamics. Inactive eolian deposits in the WRZ, comprising pan-fringing lunette and coastal dunes, were investigated to establish their depositional ages and utility as paleoenvironmental indicators. The resulting optical luminescence chronology reveals episodic lunette accretion at 60,000–45,000 yr, 12,000–13,000 yr, 2800–2600 yr, 1200 yr, and <1000 yr, with coastal dune ages clustering at 4100–4700 yr.Episodes of lunette and coastal dune accretion on the Agulhas Plain are temporally distinct, reflecting differing fundamental controls on their activity. Comparisons to previously published data also reveal that the lunettes differ in age from more ancient coastal eolianites. Lunette deposition is asynchronous between locations, reflecting the topographic and hydrological setting of the individual pans. In near-coastal settings, with limited surface recharge, lunette accretion appears to be at least partially controlled by sea level induced changes in groundwater levels. Those pans with more significant surface recharge (particularly from fluvial systems) may produce less ambiguous paleoenvironmental records, with pan status more strongly reflecting regional hydrological conditions. Lunette orientation is indicative of strong westerly winds during both the Pleistocene and Holocene. Lunette accretion would have been promoted by reduced on-shore moisture transport during the summer months, enhancing rainfall seasonality. Such conditions would have been promoted by increased continentality as the Agulhas Bank was exposed during low sea level stands.

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