EXPERIMENT ON RESPONSE OF SANDY BEACH WITH DIFFERENT CONTENTS OF SAND AND GRAVEL TO WAVES

Abstract. How storm events contribute to long-term shoreline change over decades to centuries remains an open question in coastal research. Sand and gravel coasts exhibit remarkable resilience to event-driven disturbances, and, in settings where sea level is rising, shorelines retain almost no detailed information about their own past positions. Here, we use a high-frequency, multi-decadal observational record of shoreline position to demonstrate quantitative indications of morphodynamic turbulence – “signal shredding” – in a sandy beach system. We find that, much as in other dynamic sedimentary systems, processes of sediment transport that affect shoreline position at relatively short timescales may obscure or erase evidence of external forcing. This suggests that the physical effects of annual (or intra-annual) forcing events, including major storms, may convey less about the dynamics of long-term shoreline change – and vice versa – than coastal researchers might wish.

Download Full-text

Storm Waves at the Shoreline: When and Where Are Infragravity Waves Important?

Journal of Marine Science and Engineering ◽

10.3390/jmse7050139 ◽

2019 ◽

Vol 7 (5) ◽

pp. 139 ◽

Cited By ~ 6

Author(s):

Oliver Billson ◽

Paul Russell ◽

Mark Davidson

Keyword(s):

Deep Water ◽

Water Wave ◽

Sandy Beach ◽

Transport Processes ◽

Infragravity Waves ◽

Storm Wave ◽

Wave Conditions ◽

Gravel Beaches ◽

Deep Water Wave ◽

Sand And Gravel

Infragravity waves (frequency, f = 0.005–0.05 Hz) are known to dominate hydrodynamic and sediment transport processes close to the shoreline on low-sloping sandy beaches, especially when incident waves are large. However, in storm wave conditions, how their importance varies on different beach types, and with different mixes of swell and wind-waves is largely unknown. Here, a new dataset, comprising shoreline video observations from five contrasting sites (one low-sloping sandy beach, two steep gravel beaches, and two compound/mixed sand and gravel beaches), under storm wave conditions (deep water wave height, H0 up to 6.6 m, and peak period, Tp up to 18.2 s), was used to assess: how the importance and dominance of infragravity waves varies at the shoreline? In this previously unstudied combination of wave and morphological conditions, significant infragravity swash heights (Sig) at the shoreline in excess of 0.5 m were consistently observed on all five contrasting beaches. The largest infragravity swash heights were observed on a steep gravel beach, followed by the low-sloping sandy beach, and lowest on the compound/mixed sites. Due to contrasting short wave breaking and dissipation processes, infragravity frequencies were observed to be most dominant over gravity frequencies on the low-sloping sandy beach, occasionally dominant on the gravel beaches, and rarely dominant on the compound/mixed beaches. Existing empirical predictive relationships were shown to parameterize Sig skillfully on the sand and gravel beaches separately. Deep water wave power was found to accurately predict Sig on both the sand and gravel beaches, demonstrating that, under storm wave conditions, the wave heights and periods are the main drivers of infragravity oscillations at the shoreline, with the beach morphology playing a secondary role. The exception to this was the compound/mixed beach sites where shoreline infragravity energy remained low.

Download Full-text

KARAKTERISTIK PANTAI KAWASAN PESISIR LARANTUKA DAN SEKITARNYA, P. FLORES TIMUR DAN KAWASAN PESISIR P. ADONARA BARAT

JURNAL GEOLOGI KELAUTAN ◽

10.32693/jgk.8.2.2010.188 ◽

2016 ◽

Vol 8 (2) ◽

pp. 75

Author(s):

Prijantono Astjario ◽

Ai Yuningsih

Keyword(s):

Key Words ◽

Sandy Beach ◽

Eastern Coast ◽

Coastal Morphology ◽

Coast Line ◽

Volcanic Breccia ◽

Sand And Gravel ◽

Shallow Bay ◽

Mangrove Trees

Kawasan pantai Larantuka berada di pantai timur Pulau Flores dan kaki Gunungapi Ile Mandiri membentuk bentang alam pesisir bertebing curam dan landai. Kawasan pesisir dapat diklasifikasikan dalam tiga tipe pantai, yaitu tipe pantai bertebing berbatu, pantai berpasir dan pantai berbakau. Tipe pantai bertebing berbatu berada pada kaki gunungapi dibatasi oleh lava. Tipe pantai berpasir merupakan kawasan pantai dengan bentang alam landai sedangkan kawasan pantai berbakau tersebar cukup luas khususnya pada teluk dangkal. Pulau Adonara didominasi oleh produk gunungapi tua yang terdiri dari lava, breksi gungungapi dan pasir-tufa gampingan. Kawasan pantai tipe bertebing berbatu ditempati oleh batugamping terumbu serta lava. Sedangkan tipe pantai berpasir yang membentuk bentang alam landai ditempati pasir serta kerikil volkanik dengan terkadang ditemui tumbuhan bakau. Kata kunci : kawasan pesisir, bakau, bongkah, dan lava Lanrantuka area lies on the eastern coast of Flores island and in the foot of the Ile Mandiri mountain. The Larantuka area has steep and slightly slopes. Coastal morphology can be classified into three beach types, steep and stony, sandy and mangrove beaches. The steep and stony beach lie on foot of a mountain with lava boulder. The sandy beach has slightly slope coast line and mangrove beach develops widely in area specially in the shallow bay. Adonara island is dominated by old volcanic products, which are composed of lava, volcanic breccia and calcareous-sandy tuff. The coastal type with steep and stony beach is covered by coral limestone and lava. The sandy beach has slightly slope coast line covered by sand and gravel volcanics with occasionally mangrove trees. Key words : coastal, mangrove, boulder and lava.

Download Full-text

Environmental signal shredding on sandy coastlines

10.5194/esurf-2018-72 ◽

2018 ◽

Author(s):

Eli D. Lazarus ◽

Mitchell D. Harley ◽

Chris E. Blenkinsopp ◽

Ian L. Turner

Keyword(s):

Sandy Beach ◽

Shoreline Change ◽

Storm Events ◽

Shoreline Position ◽

Sand And Gravel ◽

Open Question ◽

Short Time ◽

Observational Record ◽

Coastal Research

Abstract. How storm events contribute to long-term shoreline change over decades to centuries remains an open question in coastal research. Sand and gravel coasts exhibit remarkable resilience to event-driven disturbances, and, in settings where sea level is rising, shorelines retain almost no detailed information about their own past positions. Here, we use a detailed, multi-decadal observational record of shoreline position to demonstrate quantitative indications of morphodynamic turbulence – signal shredding – in a sandy beach system. We find that, much like other dynamic sedimentary systems, processes of sediment transport that affect shoreline position at relatively short time-scales obscure or erase physical evidence of external forcing. This suggests that large forcing events like major coastal storms, even when their effects are recorded, may convey less about the dynamics of long-term shoreline change – and vice versa – than coastal researchers might wish.

Download Full-text

Weak niche partitioning by migrating shorebirds in a single-food-type environment

Avian Biology Research ◽

10.1177/1758155919841279 ◽

2019 ◽

Vol 12 (3) ◽

pp. 109-117 ◽

Cited By ~ 1

Author(s):

Ivana Novcic

Keyword(s):

Sandy Beach ◽

Niche Partitioning ◽

Food Type ◽

Swash Zone ◽

Semipalmated Sandpiper ◽

Foraging Niche ◽

Coexisting Species ◽

Sand And Gravel ◽

Selection Of ◽

Semipalmated Sandpipers

This study examined foraging niche partitioning among coexisting species of shorebirds on a sandy beach dominated by a single food type, Horseshoe Crab ( Limulus polyphemus) eggs, where use of foraging microhabitats of limited variety is temporarily restricted due to tidal cycle. The major goal of the study was to examine whether co-occurring species differed in selection of foraging microhabitats and use of feeding techniques. Ruddy Turnstone ( Arenaria interpres), Red Knot ( Calidris canutus), and Sanderling ( Calidris alba) foraged significantly more on sand and gravel compared to pools and swash zone, Semipalmated Sandpiper ( Calidris pusilla) foraged significantly more on sand and gravel compared to swash zone, but not significantly more compared to pools, while differences in use of microhabitats by Dunlin ( Calidris alpina), and Short-billed Dowitcher ( Limnodromus griseus) were non-significant. Turnstones used digging and turning stones, and pecking significantly more than probing, Semipalmated Sandpipers used pecking significantly more than probing, while all other species used probing significantly more than pecking. Knots and Sanderlings had the highest level of overlap both in use of microhabitats and foraging techniques, while turnstones and dowitchers had the lowest. Ruddy Turnstones were the only birds that used digging and turning stones to obtain food and these two foraging methods seemed to be the most important variables discriminating turnstones from other co-occurring shorebirds. However, despite the slight differences in use of foraging methods and microhabitats by different species, this study documented weak partitioning among shorebirds, particularly between sandpipers and dowitchers. These results indicate that the short-term absence of clear niche partitioning on a local scale may occur in shorebird communities.

Download Full-text