scholarly journals Field Observations of a Multilevel Beach Cusp System and Their Swash Zone Dynamics

Geosciences ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 148
Author(s):  
Siegmund Nuyts ◽  
Zili Li ◽  
Kieran Hickey ◽  
Jimmy Murphy
Keyword(s):  
Morphological Evolution ◽  
Swash Zone ◽  
Storm Events ◽  
Survey Period ◽  
Similarity Parameter ◽  
Global Theory ◽  
Astronomical Tide ◽  
Tidal Cycles ◽  
Aerial Vehicle ◽  
Beach Cusp

This paper presents the observed morphological evolution of a multilevel beach cusp system in Long Strand, Co. Cork, Ireland. The surveys were carried out with an Unmanned Aerial Vehicle (UAV) system between March and September 2019. From this site, three levels of beach cusps on the beachface (i.e., lower beach level, mid beach level and upper beach level), and critical cusp parameters are reported, including cusp spacing, cusp elevation, cusp depth, and cusp amplitude. Thus far, such an extensive dataset has not previously been reported in the literature from a single site. The evolution of the different cusp parameters is then linked with the hydrodynamics in the study area, and new prediction theories are proposed for the different cusp parameters. The Lower beach level cusps (1 < z < 2.5 m Irish Transverse Mercator (ITM)) changed with every tide and appeared when surf-similarity parameter -ξ0 < 1.55. These cusps had a mean cusp spacing of λmean = 11.09 m, which are closely linked with the predictions of the self-organisation theory (p < 0.05). In contrast, the Mid beach level cusps (2.5 < z < 3.5 m ITM) are less dynamic compared to the Lower beach level cusps and can persist between spring tidal cycles. They had a mean cusp spacing of λmean = 18.17 m. The Upper beach level cusps (approximately z = 6 m ITM) are above astronomical tide levels and have a mean cusp spacing of λmean = 40.26 m. They did not change significantly over the survey period due to a lack of major storm events. These findings give a better understanding of the evolution of different cusp parameters for a multilevel beach cusp system and can be used to formulate a global theory regarding their change over time.

scholarly journals Use of unmanned aerial vehicles (UAVs) for mark-resight nesting population estimation of adult female green sea turtles at Raine Island

2020 ◽  
Author(s):  
Andrew Dunstan ◽  
Katherine Robertson ◽  
Richard Fitzpatrick ◽  
Jeff Pickford ◽  
Justin Meager
Keyword(s):  
Cost Effective ◽  
Accurate Method ◽  
Time Of Day ◽  
Correction Factors ◽  
Underwater Video ◽  
Survey Period ◽  
Detection Rates ◽  
Green Sea Turtles ◽  
Abundance Estimates ◽  
Aerial Vehicle

AbstractNester abundance is a key measure of the performance of the world’s largest green turtle rookery at Raine Island, Australia. Abundance surveys have been undertaken in waters adjacent to Raine Island reef using mark-resight counts by surface observer (SO), underwater video (UWV) and unmanned aerial vehicle (UAV) (since 1984, 2013 and 2016 respectively). UAV and UWV may provide more cost-effective and less biased alternatives, but estimates must be comparable with the historical estimates. Here we compare the three methods.The relative likelihood of resighting a marked turtle was significantly higher by SO than the other methods, which led to lower mark-resight population estimates than by UAV or UWV. Most (96%) variation in resighting probabilities was associated with survey period, with comparatively little variation between consecutive days of sampling or time of day. This resulted in preliminary correction factors of 1.53 and 1.73 from SO-UWV and SO-UAV, respectively. However, the SO and UWV estimates were the most similar when turtle densities were the lowest, suggesting that correction factors need to take into account turtle density and that more data are required.We hypothesise that the UAV and UWV methods improved detection rates of marked turtles because they allowed subsequent review and frame-by-frame analysis, thus reducing observer search error. UAVs were the most efficient in terms of survey time, personnel commitment and weather tolerance compared to the SO and UWV methods.This study indicates that using UAVs for in-water mark-resight turtle abundance estimation is an efficient and accurate method that can provide an accurate adjustment for historical abundance estimates. Underwater video may continue to be useful as a backup alternative to UAV surveys.

scholarly journals Wave run-up on embayed beaches. Study case: Itapocorói Bay, Southern Brazil

2017 ◽  
Vol 65 (2) ◽  
pp. 187-200 ◽  
Author(s):  
Guilherme Vieira da Silva ◽  
Paula Gomes da Silva ◽  
Rafael Sangoi Araujo ◽  
Antonio Henrique da Fontoura Klein ◽  
Elírio E. Toldo Jr.
Keyword(s):  
Wave Height ◽  
Wave Model ◽  
Swash Zone ◽  
Southern Brazil ◽  
Wave Direction ◽  
Linear Processes ◽  
Similarity Parameter ◽  
Peak Period ◽  
The Mean ◽  
Run Up

ABSTRACT This paper presents a new approach for estimating run-up on embayed beaches based on a study of the microtidal coast of Itapocorói Bay, Southern Brazil using the surf similarity parameter and wave height at break location. The four step methodology involved: 1) direct wave measurement (34 days), wave run-up measurement (19 days at 7 points within the bay), measurement of bathymetry and beach topography in the entire bay; 2) tests on available formulae to calculate wave run-up; 3) use of the SWAN spectral wave model to simulate wave parameters at breaking at each wave run-up measurement point and; 4) development of a new formula/approach to assess wave run-up on embayed beaches (in both exposed and protected areas). During the experiments the significant wave height varied from 0.5 m to 3.01 m, the mean wave period from 2.79 s to 7.76 s (the peak period varied between 2.95 s and 17.18 s), the mean wave direction from 72.5° to 141.9° (the peak direction varied from 39.2° to 169.8°) and the beach slope (tan β) from 0.041 to 0.201. The proposed formula is in good agreement with measured data for different wave conditions and varying degrees of protection. The analysis demonstrates that although R² varies from 0.52 to 0.75, the wave run-up distribution over the measurements agreed well with the proposed model, as shown by quantile-quantile analysis (R²=0.98 to 0.99). The errors observed in individual cases may be related to errors of measurements, modeling and to non-linear processes in the swash zone, such as infragavity waves.

scholarly journals Experimental Study on the Influence of an Artificial Reef on Cross-Shore Morphodynamic Processes of a Wave-Dominated Beach

Water ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2947 ◽  
Author(s):  
Yue Ma ◽  
Cuiping Kuang ◽  
Xuejian Han ◽  
Haibo Niu ◽  
Yuhua Zheng ◽  
...  
Keyword(s):  
Morphological Evolution ◽  
Artificial Reef ◽  
Morphological Features ◽  
Coastal Protection ◽  
Swash Zone ◽  
State Transformation ◽  
Irregular Wave ◽  
Wave Flume ◽  
The Cross ◽  
Run Up

Artificial reefs are being implemented around the world for their multi-functions including coastal protection and environmental improvement. To better understand the hydrodynamic and morphodynamic roles of an artificial reef (AR) in beach protection, a series of experiments were conducted in a 50 m-long wave flume configured with a 1:10 sloping beach and a model AR (1.8 m long × 0.3 m high) with 0.2 m submergence depth. Five regular and five irregular wave conditions were generated on two types of beach profiles (with/without model AR) to study the cross-shore hydrodynamic and morphological evolution process. The influences of AR on the processes are concluded as follows: (1) AR significantly decreases the incident wave energy, and its dissipation effect differs for higher and lower harmonics under irregular wave climates; (2) AR changes the cross-shore patterns of hydrodynamic factors (significant wave height, wave skewness and asymmetry, and undertow), leading to the movement of shoaling and breaking zones; (3) the beach evolution is characterized by a sandbar and a scarp which respectively sit at a higher and lower location on the profile with AR than natural beach without AR; (4) the cross-shore morphological features indicate that AR can lead to beach state transformation toward reflective state; (5) the scarp retreat process can be described by a model where the scarp location depends linearly on the natural exponential of time with the fitting parameters determined by wave run-up reduced by AR. This study demonstrates cross-shore effects of AR as a beach protection structure that changes wave dynamics in surf and swash zone, reduces offshore sediment transport, and induces different morphological features.

scholarly journals EXTREME SCENARIOS AT THE GERMAN NORTH SEA COAST A NUMERICAL MODEL STUDY

2011 ◽  
Vol 1 (32) ◽  
pp. 26 ◽  
Author(s):  
Gerd Bruss ◽  
Babriele Gönnert ◽  
Roberto Mayerle
Keyword(s):  
North Sea ◽  
Numerical Models ◽  
High Tide ◽  
Water Levels ◽  
Nonlinear Interactions ◽  
Storm Events ◽  
The North ◽  
Astronomical Tide ◽  
Sea Coast ◽  
North Sea Coast

A procedure, based on numerical models is proposed to investigate the processes involved during conditions of extreme water levels within the outer Elbe estuary at the German North Sea coast. Nonlinear interactions between the different processes are analyzed and adverse combinations are simulated yielding new scenarios. Various conditions in the astronomical tide, three major storm events over the North Sea, several external surges and an increase in the mean sea level are analyzed. Techniques for the modeling of each of the isolated processes are developed and individually verified. The isolated processes are temporally shifted relative to each other and superimposed in various combinations. The results obtained from the present method, provide new insights into the nonlinear interactions between the involved processes. Generally, the effects of the processes seem to be reduced in superpositions with high absolute water levels. However, due to the large scatter of the results no general relations are found. New extreme scenarios are determined by iterative maximizations of the peak water level of different superpositions around spring high tide.

scholarly journals Mud Flow Reconstruction by Means of Physical Erosion Modeling, High-Resolution Radar-Based Precipitation Data, and UAV Monitoring

Geosciences ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 427 ◽  
Author(s):  
Phoebe Hänsel ◽  
Andreas Kaiser ◽  
Arno Buchholz ◽  
Falk Böttcher ◽  
Stefan Langel ◽  
...  
Keyword(s):  
High Resolution ◽  
Soil Erosion ◽  
Precipitation Data ◽  
Storm Events ◽  
Erosion Modeling ◽  
Erosion Risk ◽  
Vehicle Monitoring ◽  
High Resolution Radar ◽  
Aerial Vehicle ◽  
Physical Erosion

Storm events and accompanying heavy rain endanger the silty soils of the fertile and intensively-used agricultural landscape of the Saxon loess province in the European loess belt. In late spring 2016, persistent weather conditions with repeated and numerous storm events triggered flash floods, landslides, and mud flows, and caused severe devastation to infrastructure and settlements throughout Germany. In Saxony, the rail service between Germany and the Czech Republic was disrupted twice because of two mud flows within eight days. This interdisciplinary study aims to reconstruct the two mud flows by means of high-resolution physical erosion modeling, high-resolution, radar-based precipitation data, and Unmanned Aerial Vehicle monitoring. Therefore, high-resolution, radar-based precipitation data products are used to assess the two storm events which triggered the mud flows in this unmonitored area. Subsequently, these data are used as meteorological input for the soil erosion model EROSION 3D to reconstruct and predict mud flows in the form of erosion risk maps. Finally, the model results are qualitatively validated by orthophotos generated from images from Unmanned Aerial Vehicle monitoring and Structure from Motion Photogrammetry. High-resolution, radar-based precipitation data reveal heavy to extreme storm events for both days. Erosion risk maps show erosion und deposition patterns and source areas as in reality, depending on the radar-based precipitation product. Consequently, reconstruction of the mud flows by these interdisciplinary methods is possible. Therefore, the development of an early warning system for soil erosion in agricultural landscapes by means of E 3D and high-resolution, radar-based precipitation forecasting data is certainly conceivable.

scholarly journals BEACH CUSPS AT POINT REYES AND DRAKES BAY BEACHES, CALIFORNIA

1980 ◽  
Vol 1 (17) ◽  
pp. 53 ◽  
Author(s):  
R.G. Dean ◽  
E.M. Maurmeyer
Keyword(s):  
Sediment Transport ◽  
Swash Zone ◽  
Rip Currents ◽  
Qualitative And Quantitative ◽  
Scientific Curiosity ◽  
Point Reyes ◽  
Quantitative Understanding ◽  
Beach Cusps ◽  
Beach Cusp ◽  
Predictive Relationship

Beach cusps, fairly common and periodic features along many shorelines have been the focus of numerous investigations. The primary efforts have been directed toward (1) determining a causative mechanism for their formation; (2) describing qualitatively the associated water motions and sediment transport; and (3) developing a predictive relationship for their spacing. As in other problems in nearshore dynamics (e.g. rip currents), it may be that there are various valid explanations for different occurrences of beach cusps. In addition to satisfying scientific curiosity, an improved qualitative and quantitative understanding of beach cusp mechanisms would contribute substantially to swash zone dynamics and to nearshore hydrodynamics and sediment transport in general. This paper describes a series of measurements of beach cusps and associated parameters carried out at Point Reyes and Drakes Bay beaches in northern California during the summers of 1977-1979. An attempt to idealize the beach cusp topography and the resulting swash hydromechanics led to a possible relationship between beach cusp spacing and swash parameters in which the spacing is linearly related to maximum swash excursion.

Sign in / Sign up

Export Citation Format

Share Document