Understanding Lateral Marsh Edge Erosion with Terrestrial Laser Scanning (TLS)

Coastal wetlands are a crucial buffer zone between land and sea but lateral erosion threatens their long-term sustainability. Better understanding of the forces leading to lateral marsh retreat will benefit the assessment of management options applied to mitigate the erosion. Terrestrial Laser Scanning (TLS), Light Detection and Ranging (lidar), and associated technologies are increasingly being used to assess this erosion. The central objective of this study was to identify a methodology for measuring marsh edge erosion with a TLS and correlate that erosion with exposed roots and incident wave energy. We quantified edge erosion across multiple temporal and spatial scales using a TLS, showing greater than one meter of lateral erosion over a 318-day period. We then evaluated the relationships between the erosion and incident wave energy along with erosion and vegetation roots. Wave height and erosion was strongly related (r2 = 0.99), while vegetation roots did not show an apparent effect. We discuss the challenges that arise from using TLS equipment, TLS data sets, and the use of voxels to measure marsh edge erosion.

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Terrestrial Laser Scanning for Vegetation Analyses with a Special Focus on Savannas

Remote Sensing ◽

10.3390/rs13030507 ◽

2021 ◽

Vol 13 (3) ◽

pp. 507

Author(s):

Tasiyiwa Priscilla Muumbe ◽

Jussi Baade ◽

Jenia Singh ◽

Christiane Schmullius ◽

Christian Thau

Keyword(s):

Remote Sensing ◽

Vegetation Structure ◽

Laser Scanning ◽

Spatial Scales ◽

Terrestrial Laser Scanning ◽

Point Clouds ◽

Parameter Extraction ◽

Airborne Lidar ◽

Special Focus ◽

Vegetation Parameter

Savannas are heterogeneous ecosystems, composed of varied spatial combinations and proportions of woody and herbaceous vegetation. Most field-based inventory and remote sensing methods fail to account for the lower stratum vegetation (i.e., shrubs and grasses), and are thus underrepresenting the carbon storage potential of savanna ecosystems. For detailed analyses at the local scale, Terrestrial Laser Scanning (TLS) has proven to be a promising remote sensing technology over the past decade. Accordingly, several review articles already exist on the use of TLS for characterizing 3D vegetation structure. However, a gap exists on the spatial concentrations of TLS studies according to biome for accurate vegetation structure estimation. A comprehensive review was conducted through a meta-analysis of 113 relevant research articles using 18 attributes. The review covered a range of aspects, including the global distribution of TLS studies, parameters retrieved from TLS point clouds and retrieval methods. The review also examined the relationship between the TLS retrieval method and the overall accuracy in parameter extraction. To date, TLS has mainly been used to characterize vegetation in temperate, boreal/taiga and tropical forests, with only little emphasis on savannas. TLS studies in the savanna focused on the extraction of very few vegetation parameters (e.g., DBH and height) and did not consider the shrub contribution to the overall Above Ground Biomass (AGB). Future work should therefore focus on developing new and adjusting existing algorithms for vegetation parameter extraction in the savanna biome, improving predictive AGB models through 3D reconstructions of savanna trees and shrubs as well as quantifying AGB change through the application of multi-temporal TLS. The integration of data from various sources and platforms e.g., TLS with airborne LiDAR is recommended for improved vegetation parameter extraction (including AGB) at larger spatial scales. The review highlights the huge potential of TLS for accurate savanna vegetation extraction by discussing TLS opportunities, challenges and potential future research in the savanna biome.

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Evaluation of Incident Wave Energy in Flume Tests

Coastal Engineering 1986 ◽

10.1061/9780872626003.093 ◽

1987 ◽

Author(s):

Eliezer Kit ◽

Oded Gottlieb ◽

Dov S. Rosen

Keyword(s):

Incident Wave ◽

Wave Energy ◽

Flume Tests ◽

Incident Wave Energy

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FIELD EXPERIMENT ON BEACH GRAVEL TRANSPORT

Coastal Engineering Proceedings ◽

10.9753/icce.v16.101 ◽

1978 ◽

Vol 1 (16) ◽

pp. 101 ◽

Cited By ~ 1

Author(s):

Masataro Hattori ◽

Takasuke Suzuki

Keyword(s):

Field Experiment ◽

Incident Wave ◽

Wave Energy ◽

Transport Processes ◽

Central Japan ◽

Selective Transport ◽

Longshore Transport ◽

Wave Energy Flux ◽

The Mean ◽

Incident Wave Energy

To examine the longshore transport processes of beach gravels under wave action, a field experiment was performed by tracing the dacite blocks injected on Fuji Coast, Shizuoka Prefecture, Central Japan. The mean dislocating velocity of the tracer was 2 to 3 m/day under normal sea conditions, while under storm conditions it reached about 400 m/day. This -velocity was fairly proportional to the longshore component of incident wave energy flux. The longshore variations of the size and shape of beach gravels were mainly resulted from the progressive attrition and impact breakage of beach gravels rather than from the selective transport.

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Do longshore bars shelter the shore?

Journal of Fluid Mechanics ◽

10.1017/s0022112099007168 ◽

2000 ◽

Vol 404 ◽

pp. 251-268 ◽

Cited By ~ 34

Author(s):

JIE YU ◽

CHIANG C. MEI

Keyword(s):

Spatial Distribution ◽

Incident Wave ◽

Wave Energy ◽

Phase Relation ◽

Bragg Reflection ◽

Qualitative Change ◽

Numerical Calculations ◽

Reflected Waves ◽

Incident Waves ◽

Incident Wave Energy

In most past theories on Bragg reflection of waves by a finite patch of rigid bars, only outgoing waves are allowed on the transmission side, simulating the effect of an idealized shoreline where all the incident wave energy is consumed by breaking. In these theories the amplitudes of both the incident and reflected waves are found to decrease monotonically over the bar patch in the shoreward direction. This result has motivated the idea of artificially constructing bars to protect a beach from incident waves. However, some numerical calculations have suggested that this tendency does not always hold when there is some reflection from the shore. We show here that with finite reflection by the shoreline the spatial distribution of wave energy over the patch can indeed be reversed, indicating that the mechanism can increase the hazards to the beach. The phase relation between the bars and the shoreline reflection is found to be the key to this qualitative change of wave response.

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RESEARCHES ON SEA-WALLS

Coastal Engineering Proceedings ◽

10.9753/icce.v12.88 ◽

1970 ◽

Vol 1 (12) ◽

pp. 88

Author(s):

S. Nagal

Keyword(s):

Incident Wave ◽

Wave Energy ◽

Precast Concrete ◽

Recent Decade ◽

Point Of View ◽

Industrial Firms ◽

Wave Overtopping ◽

Port Facilities ◽

Sea Wall ◽

Incident Wave Energy

In the recent decade, very wide areas of sea where the depths of water are from several meters to ten meters or more during storms have been reclaimed for industrial firms and port facilities in many places in Japan As the incident wave energy in such cases is very large at the sea-walls, the protection of the reclaimed lands from wave overtopping by the conventional sea-walls of vertical type or composite-slope«and-berai type is generally impossible from an economical point of view In Japan a special type of sea-wall, which is of such a type that a rubble-mound covered with specially shaped precast concrete armor blocks is built in front of the sea-wall to absorb most of the incident wave energy, has been constructed to protect the reclaimed lands from wave overtopping Most of the seawalls have been proved satisfactory after passing of typhoons over or near the sea-walls The design of the sea-walls is presented here in by showing the comparisons between the experiments and prototypes during typhoons.

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Model Experiment on an OWC-Type Wave-Energy Converter With Hydraulic Power Take-Off

21st International Conference on Offshore Mechanics and Arctic Engineering, Volume 4 ◽

10.1115/omae2002-28171 ◽

2002 ◽

Cited By ~ 2

Author(s):

Torkel Bjarte-Larsson ◽

Per Magne Lillebekken ◽

Jo̸rgen Hals ◽

Johannes Falnes

Keyword(s):

Incident Wave ◽

Wave Energy ◽

Wave Energy Converter ◽

Laboratory Model ◽

Energy Converter ◽

Hydraulic Power ◽

Optimum Load ◽

Wave Channel ◽

Period 2 ◽

Incident Wave Energy

A wave-energy converter of the OWC type is described, in which the absorbed wave energy is converted to useful energy by means of a hydraulic power take-off. Means are provided to enable the float to be latched for phase control. The float is connected to a piston pump, which pumps water from the level of the water in the wave channel to a higher level, which is adjustable. By means of measurements from three wave gauges (two on the upstream side and one on the downstream side) the incident wave energy and the absorbed wave energy are derived. For a down-scaled laboratory model, resonance is obtained with an incident sinusoidal wave of period 1 s. With optimum load, the converted useful hydraulic energy is a fraction of 0.2 of the incident wave energy. The absorbed wave energy is then 0.6 units of the incident wave energy. With wave period 2 s and optimum load, these energy fractions are 0.03 and 0.13, which are increased to 0.05 and 0.21, respectively, when latching control is applied.

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Regularly-spaced grooves on shore platforms in north Northumberland, UK

Proceedings of the Yorkshire Geological Society ◽

10.1144/pygs2019-006 ◽

2020 ◽

Vol 63 (2) ◽

pp. 124-134

Author(s):

Alison M. Tymon ◽

Barry G. Tymon

Keyword(s):

Incident Wave ◽

Wave Energy ◽

Surf Zone ◽

High Water ◽

Edge Waves ◽

Shore Platform ◽

Bedding Planes ◽

High Water Mark ◽

Incident Wave Energy ◽

Shore Platforms

Unusual regularly-spaced grooves are found between low water mark (LWM) and high water mark (HWM) on several shore platforms in north Northumberland. References in the literature are sparse, so data were collected to establish the nature of the grooves and to elucidate the processes that might have formed them. Groove formation is confined to strata with widely spaced bedding planes on shore platforms dipping at no more than 5° towards the sea. The grooves are symmetrical, bifurcation is common and grooves on sandstones are deeper and more sinuous than those on limestones. Grooves at mid-tide levels are wider than grooves near LWM and HWM and the trend of the grooves is not related to joint trends. The process that has formed the characteristically smooth surfaces of the grooves is considered to be abrasion by sand and pebbles carried by waves in the surf zone of the shore platform. The width of the grooves is remarkably regular, and it is suggested that this may be due to the effects of the increase in incident wave energy given by edge waves.

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EVALUATION OF INCIDENT WAVE ENERGY IN FLUME TEST

Coastal Engineering Proceedings ◽

10.9753/icce.v20.93 ◽

1986 ◽

Vol 1 (20) ◽

pp. 93

Author(s):

Eliezer Kit ◽

Oded Gottlieb ◽

Dov S. Rosen

Keyword(s):

Least Squares ◽

Incident Wave ◽

Wave Energy ◽

Least Squares Method ◽

Stationary Wave ◽

Residual Energy ◽

Irregular Waves ◽

Wave Spectra ◽

Reflected Wave ◽

Incident Wave Energy

A two dimensional model study, carried out for a structure in a flume using irregular waves, presents the problem of determining the relationship between the total incident wave energy attacking the structure and its response to that attack (displacements, forces, etc.) in various sea states, The total incident wave energy can be evaluated indirectly only, because the wave energy measured in the flume contains an extent of residual wave energy in addition to that generated by the wave machine. This residual energy consists of the re-reflected wave energy from the paddle of the wave machine, assuming the existence of quasi-stationary wave conditions in the flume. A method originally presented by Gravesen et al. (1974), was applied in this study to evaluate the total incident wave energy. In view of the results obtained by this method, a physically more sound refinement is proposed for the evaluation of the total incident wave energy (and characteristic wave height). Results of model tests were analyzed by the CAMERI refinement and compared with the Gravesen method and with a cross-spectral least squares method, separating incident and reflected wave spectra from wave spectra measured in the flume, Good agreement was found between the results obtained employing the CAMERI refinement and the cross-spectral least squares method, Advantages and drawbacks of these methods are indicated,

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