Exploring the role of vegetation and sediment supply to coastal dune states using integrated process-based modelling

2020 ◽  
Author(s):  
Susana Costas ◽  
Katerina Kombiadou ◽  
Dano Roelvink
Keyword(s):  
Coastal Management ◽  
Coastal Dune ◽  
Sediment Supply ◽  
Vegetation Coverage ◽  
Maximum Efficiency ◽  
Ecological Processes ◽  
Morphological Response ◽  
Shoreline Position ◽  
Coupled Modelling ◽  
Dune Morphology

<p>Coastal dune morphology is largely controlled by the availability of sand to be transferred from the beach and the capacity of the vegetation to trap and retain the moving sand grains. The resultant coastal dune morphology is, in turn, key to achieve maximum efficiency of nature-based solutions that plan the construction of such aeolian features. Therefore, developing approaches that integrate key processes becomes crucial, especially in order to efficiently design and test solutions that meet the timescale requirements of coastal management. The process-based XBeach-Duna model has been developed to integrate nearshore, aeolian and ecological processes across the beach-dune profile, thus allowing long-term simulation of complex coastal features and feedbacks. Here, we explore the potential of this coupled modelling solution to simulate the morphological response of coastal dunes to changes in sediment supply and vegetation cover over decadal timescales. Simulations show the capacity of the approach to reproduce the natural response to changes in sediment supply, shifting the shoreline position and simultaneously modifying the overall shape of the dune, within a range of dimensions that are in agreement with observations. In general, narrow and low dunes are formed under high supply conditions, wide and high dunes develop if sediment supply is low and the shoreline position stable, while narrower and higher dunes are created after a relative drop in sediment supply that induces a negative budget. Denser vegetation coverage, on the other hand, favours taller dune morphologies, however the influence of sediment supply and receding shoreline positions to plant growth are non-linear and, in turn, produce feedbacks that cascade to the morphology of the dune itself. These results demonstrate the capacity of the approach to reproduce different dune states, resulting from alternative evolutionary pathways, and its potential to identify coastal dune (in)stability domains and critical morphological shifts, factors that are key to better understand the efficiency of dunes as nature-based solutions for coastal management.</p><p>This work was supported by the project PTDC/CTA-GFI/28949/2017, funded by the Portuguese Foundation for Science and Technology.</p>

scholarly journals Directional dependency and coastal framework geology: implications for barrier island resilience

2018 ◽  
Vol 6 (4) ◽  
pp. 1139-1153 ◽  
Author(s):  
Phillipe A. Wernette ◽  
Chris Houser ◽  
Bradley A. Weymer ◽  
Mark E. Everett ◽  
Michael P. Bishop ◽  
...  
Keyword(s):  
Coastal Management ◽  
Spatial Scales ◽  
Moving Average ◽  
Barrier Island ◽  
Arfima Models ◽  
Societal Pressure ◽  
Dune Morphology ◽  
Padre Island ◽  
National Seashore

Abstract. Barrier island transgression is influenced by the alongshore variation in beach and dune morphology, which determines the amount of sediment moved landward through wash-over. While several studies have demonstrated how variations in dune morphology affect island response to storms, the reasons for that variation and the implications for island management remain unclear. This paper builds on previous research by demonstrating that paleo-channels in the irregular framework geology can have a directional influence on alongshore beach and dune morphology. The influence of relict paleo-channels on beach and dune morphology on Padre Island National Seashore, Texas, was quantified by isolating the long-range dependence (LRD) parameter in autoregressive fractionally integrated moving average (ARFIMA) models, originally developed for stock market economic forecasting. ARFIMA models were fit across ∼250 unique spatial scales and a moving window approach was used to examine how LRD varied with computational scale and location along the island. The resulting LRD matrices were plotted by latitude to place the results in the context of previously identified variations in the framework geology. Results indicate that the LRD is not constant alongshore for all surface morphometrics. Many flares in the LRD plots correlate to relict infilled paleo-channels, indicating that the framework geology has a significant influence on the morphology of Padre Island National Seashore (PAIS). Barrier island surface morphology LRD is strongest at large paleo-channels and decreases to the north. The spatial patterns in LRD surface morphometrics and framework geology variations demonstrate that the influence of paleo-channels can be asymmetric (i.e., affecting beach–dune morphology preferentially in one direction alongshore) where the alongshore sediment transport gradient was unidirectional during island development. The asymmetric influence of framework geology on coastal morphology has long-term implications for coastal management activities because it dictates the long-term behavior of a barrier island. Coastal management projects should first seek to assess the framework geology and understand how it influences coastal processes in order to more effectively balance long-term natural variability with short-term societal pressure.

Coastal dune mobility over the past century: A global review

2020 ◽  
Vol 44 (6) ◽  
pp. 814-836 ◽  
Author(s):  
Jinjuan Gao ◽  
David M Kennedy ◽  
Teresa M Konlechner
Keyword(s):  
Human Activities ◽  
Vegetation Cover ◽  
Dominant Role ◽  
Coastal Dunes ◽  
Mediterranean Area ◽  
Global Scale ◽  
Coastal Dune ◽  
Sediment Supply ◽  
Past Century ◽  
The Past

The mobility of coastal dunes is characterised by bio-geomorphological responses related to change in boundary conditions, particularly sediment supply, wind and vegetation cover, as well as human activities. There remains uncertainty regarding the relative importance of these drivers on dune mobility at a global scale. In this study, trends and dominant drivers of coastal dune mobility are synthesised through the literature review focusing on shifts in dune mobility over the last century (1870–2018). In total, 176 individual dunes, with 55 dunes from the Europe-Mediterranean area, 23 from Africa, 30 from North America, 23 from South America, 20 from Oceania and 23 from Asia, are reviewed in this work. The results show that there is a worldwide trend of dune stabilisation, with 93% (164 out of 176) of the reviewed sites showing a loss of bare sand area due to an increase in vegetation cover and urbanisation expansion. Multiple factors have contributed to the stabilisation process, including (a) land-use change such as the change of traditional farming practises, coastal urbanisation and tourism development; (b) dune stabilisation projects; (c) sediment decline caused by the riverine and coastal constructions; and (d) change in climate (i.e. the decrease in windiness, and the increase in temperature and rainfall) and storms. Our results suggest human intervention played a dominant role in altering dune mobility for most dunes during the past century, while climate and storms are also important drivers, especially for dune sites with limited human activities.

scholarly journals Long-range dependence in coastal framework geology: Asymmetries and implications for barrier island resiliency

2018 ◽  
Author(s):  
Phillipe Wernette ◽  
Chris Houser ◽  
Bradley Weymer ◽  
Mark Everett ◽  
Michael Bishop ◽  
...  
Keyword(s):  
Long Range ◽  
Coastal Management ◽  
Moving Average ◽  
Barrier Island ◽  
Long Range Dependence ◽  
The North ◽  
Arfima Models ◽  
Societal Pressure ◽  
Dune Morphology

Abstract. Barrier island transgression is influenced by the alongshore variation in beach and dune morphology, which determines the amount of sediment moved landward through washover. While several studies have demonstrated how variations in dune morphology affect island response to storms, the reasons for that variation and the implications for island management remain unclear. This paper builds on previous research by demonstrating that the framework geology can influence beach and dune morphology asymmetrically alongshore. The influence of relict paleo-channels on beach and dune morphology on Padre Island National Seashore, Texas was quantified by isolating the long-range dependence (LRD) parameter in autoregressive fractionally-integrated moving average (ARFIMA) models. ARFIMA models were fit across all scales and a moving window approach was used to examine how LRD varied with computational scale and location along the island. The resulting LRD matrices were plotted by latitude to place the results in context of previously identified variations in the framework geology. Results indicate that the LRD is not constant alongshore for all surface morphometrics. Many flares in the LRD plots correlate to relict infilled paleo-channels in the framework geology, indicating that the framework geology has a significant influence on the morphology of PAIS. Barrier island surface morphology LRD is strongest at large paleo-channels and decreases to the north. The spatial patterns in LRD surface morphometrics and framework geology variations demonstrate that the influence of paleo-channels in the framework geology can be asymmetric where the alongshore sediment transport gradient was unidirectional during island development. The asymmetric influence of framework geology on coastal morphology has long-term implications for coastal management activities because it dictates the long-term behavior of a barrier island. Coastal management projects should first seek to understand how the framework geology influences coastal processes in order to more effectively balance long-term natural variability with short-term societal pressure.

Implementing a coastal dune vulnerability index (CDVI) to support coastal management in different settings (Brazil and Italy)

2019 ◽  
Vol 180 ◽  
pp. 104916 ◽  
Author(s):  
Duccio Bertoni ◽  
Giovanni Sarti ◽  
Fernanda Alquini ◽  
Daniela Ciccarelli
Keyword(s):  
Coastal Management ◽  
Vulnerability Index ◽  
Coastal Dune

Beach Erosion Arising from Artificial Land Modification

2007 ◽  
Vol 2 (1) ◽  
pp. 29-36 ◽  
Author(s):  
Takaaki Uda ◽  
Keyword(s):  
Land Management ◽  
Coastal Management ◽  
Scientific Research ◽  
Sediment Supply ◽  
Beach Erosion ◽  
Fluvial Sediment ◽  
The Public

The cause of beach erosion in Japan is classified into seven types. Of these, examples associated with the formation of wave-shelter zones and decreased fluvial sediment supply were studied, typified by changes in beaches at the Shimobara fishing port and along the Enshu-nada coast caused by decreased fluvial sediment supply from the Tenryu River. Such erosion is closely related to land management and the "sector-by-sector" system in Japan. The prevention of beach erosion thus requires both scientific research and improvement in coastal management through enhancing the public consensus.

scholarly journals Morphodynamic regime change in a reconstructed lowland stream

2014 ◽  
Vol 2 (1) ◽  
pp. 279-293 ◽  
Author(s):  
J. P. C. Eekhout ◽  
R. G. A. Fraaije ◽  
A. J. F. Hoitink
Keyword(s):  
Riparian Vegetation ◽  
Morphological Changes ◽  
Initial Period ◽  
Sediment Supply ◽  
Morphological Response ◽  
Lowland Stream ◽  
Growing Seasons ◽  
Initial Stage ◽  
Two Stages ◽  
Water Level Measurements

Abstract. With the aim to establish and understand morphological changes in response to channel reconstruction, a detailed monitoring plan was implemented in a lowland stream called Lunterse Beek, located in the Netherlands. Over a period of almost 2 years, the monitoring programme included serial morphological surveys, continuous discharge and water level measurements, and riparian vegetation mapping, from photographs and field surveys. Morphological processes occurred mainly in the initial period, before riparian vegetation developed. The initial period was largely dominated by upstream sediment supply, which was associated with channel incision upstream from the study area. Herbaceous vegetation started to develop approximately 7 months after channel reconstruction. The monitoring period included two growing seasons. A clear increase of riparian vegetation cover from first to the second year was observed. Detailed morphological and hydrological data show a marked difference in morphological behaviour between the pre-vegetation and post-vegetation stage. A linear regression procedure was applied to relate morphological activity to time-averaged Shields stress. In the initial stage after channel reconstruction, with negligible riparian vegetation, channel morphology adjusted, showing only a weak response to the discharge hydrograph. In the subsequent period, morphological activity in the channel showed a clear relation with discharge variation. The two stages of morphological response to the restoration measures may be largely associated with the upstream sediment supply in the initial period. Riparian vegetation may have played a substantial role in stabilizing the channel banks and floodplain area, gradually restricting the morphological adjustments to the channel bed.

scholarly journals Morphology and Formation of an Holocene Coastal Dune Field, Bruce Peninsula, Ontario

2007 ◽  
Vol 42 (2) ◽  
pp. 163-170 ◽  
Author(s):  
Robin G. D. Davidson-Arnott ◽  
Natalia M. Pyskir
Keyword(s):  
Wave Exposure ◽  
Coastal Dune ◽  
Sediment Supply ◽  
Lake Huron ◽  
Lake Levels ◽  
Dune Field ◽  
Dune Ridge

ABSTRACT This paper describes a dune field on the gently-sloping Lake Huron shoreline of the Bruce Peninsula, Ontario. The inland boundary is marked by a prominent dune ridge 60 m wide and up to 30 m high, which extends parallel to the shoreline for about 19 km, and was formed about 5000 years BP near the end of the Nipissing transgression. The islands and rock reefs which protect the modern shoreline were submerged under the higher lake levels, giving rise to a relatively straight, exposed beach from which sediment was supplied for building the dune ridge. Dunes formed between this ridge and the modern shoreline during the post-Nipissing regression decrease in height and continuity, reflecting decreased sediment supply associated with regression and reduced wave exposure as the offshore islands emerged. The sequence described here supports previous conclusions that transgressions are associated with periods of coastal dune formation and instability.

Sign in / Sign up

Export Citation Format

Share Document