Coastal erosion and mitigation methods – Global state of art

521-530Coastal erosion is assuming large proportions these days. Global climate change coupled with local attributes is eroding the coasts of the world in alarming proportions. Most of the conventional protection methods are hard, short lived, expensive and not eco-friendly. Trend in coastal erosion mitigation and protection has been shifting these days towards soft but novel, eco-friendly methods. Pro-active methods are being developed and used which are eco-friendly, construction-friendly, cheaper and which also reasonably address the root cause of the problem without much ‘side effects’. Many non-traditional ways to armor, stabilize or restore beaches, including the use of patented precast concrete units, geotextile sand-filled bags, green belts, bio-engineering, sand fencing, beach-face dewatering systems, integrated costal protection methods are being used. Retreat from the coast is also thought about, in many circles. Present study consists the global coastal erosion scenario and also some of the state of the art soft and pro-active erosion mitigation methods

A comparative study on extraction of buildings from Quickbird-2 satellite imagery with & without fusion

Extraction of building from very high resolution satellite imagery is a challenging task. Many automatic algorithms are proposed to extract buildings from remote sensing imageries, but most of the algorithms detect only rectangular buildings very effectively (i.e. buildings with the same size and shape). In this paper, an attempt is made to extract buildings with different shape, size, color and pattern from Quickbird-2 imagery. In the automatic method, firstly the adaptive k means clustering algorithm is performed to classify the pixels into a number of classes which then is followed by morphological operators to extract the buildings. The manual method is also implemented to extract building feature. Consequently, both, the automatic and manual methods are adopted on the original Multispectral (MS) image and on the fused image obtained by fusing Quickbird-2 Panchromatic (Pan) image with MS image using the Fuze Go method. The performance of both the methods for the extraction of buildings is evaluated using qualitative and metric analysis. The experimental results show that both the methods are performed reasonably well. However, improving the spatial resolution of the original MS image by fusion helps to determine the buildings information more precisely in terms of spatially as well as spectrally

Transmission studies on horizontal interlaced multi-layer moored floating pipe breakwater (HIMMFPB) with three layers of pipes

722-728Present study consists part of the series of physical model scale experiments conducted for the study of the transmission characteristics of horizontal interlaced multi-layer moored floating pipe breakwater (HIMMFPB). Studies were conducted on physical models of the floating breakwater with three layers of PVC pipes, wave steepness, Hi/gT2 (Hi=incident wave height, g=acceleration due to gravity and T=wave period) varying from 0.063 to 0.936; relative width, W/L (W=width of the breakwater) varying from 0.4 to 2.65 and relative spacing of pipes, S/D=2 (S=horizontal c/c spacing of pipes and D=diameter of the pipes). Transmitted wave height is measured and the collected data is analyzed by plotting non-dimensional graphs depicting the variation of Kt (transmission coefficient) with Hi/gT2for various values of d/W (d=water depth) varying from 0.082 to 0.276 and Kt with W/L for different values of Hi/d which was varied from 0.06 to 0.450. It is observed that Kt decreases as Hi/gT2 increases for the range of d/W values used in the study. It is also observed that Kt decreases with an increase in W/L for the range of Hi/d values used. Maximum wave attenuation achieved in the study with the present breakwater configurations is 78.62%. </span

Software for analysis and design of concrete sheet pile quay wall with relieving platform - RELPT6.0

Abstract: The analysis and design of sheet pile structure involves problems of complex soil structure interaction. The actual performance of the sheet pile for the given site conditions is found to be very difficult to predict as it is influenced by various parameters such as, the angle of internal friction, position of the ground water table, position of anchor, density of soil, tidal variation, surcharge load, type of construction etc. Sheet pile quay wall with relieving platform is suitable wherever unsuitable soil prevents usage of conventional anchorages and large superimposed loads from super structure requiring bearing piles to support them. The analysis of sheet pile wall with relieving platform for layered soil is based on the iterative technique, which when performed manually can be extremely tedious. A software RELPT6.0 has been developed based on the deterministic classical design approach for the analysis and design of sheet pile wall with relieving platform, adhering to the Indian standard codes; using Visual basic 6.0. The software provides the embedded depth required for the stability of the sheet pile quay wall, loads on each pile and the structural design of the cross section of the quay wall, supporting piles and the platform. The software is event driven and extremely user friendly with graphical outputs, which enables the user to analyze the outputs more accurately. The outputs of the software are compared with the manually obtained results and the variation is found to be quite small. This paper presents an outline of the procedure adopted for the analysis and design of analysis and design of sheet pile quay wall with relieving platform using RELPT6.0

Sliding stability analysis of emerged quarter circle breakwater with varying seaside perforations

1428-1435In the present study, an attempt has been made to study the sliding stability of seaside perforated Quarter circle breakwater (QBW) models. Experiments were conducted in a 2D monochromatic wave flume to study the minimum (critical) weight required to resist the sliding of emerged seaside perforated quarter circle breakwater models with radius 0.55 m and ratio of spacing to diameter of perforations (S/D) equal to 2, 2.5, 3, 4 and 5. From the results it was observed that the non-dimensional stability parameter (W/γHi2) is always decreasing with the increase in wave steepness, Hi/gT2, but increasing with increase in ratio of water depth to height of the breakwater structure or relative water depth (d/hs) and S/D. Minimum W/γHi2 was observed corresponding to S/D=2.5 and d/hs= 0.569

Bathymetry Mapping Using Landsat 8 Satellite Imagery

AbstractBathymetry is the science of determining the topography of the seafloor. Bathymetry data is used to generate navigational charts, seafloor profile, biological oceanography, beach erosion, sea level rise, etc. A number of methods are available for determining ocean bathymetry, using either active sensor such as sonar, lidar or passive multispectral imagery such as Ikonos, WorldView and Landsat. Determining the bathymetry using sonar and LiDAR is very expensive, while Ikonos and Worldview are commercially available multispectral satellite platforms whereas Landsat satellite imagery provides a free and publicly available data. Therefore, the present study makes an attempt to determine the bathymetry mapping of the southwest coast of India (13° 0’ 0” N and 74°50’ 0” E) by applying the ratio transform algorithm on the blue and green bands of Landsat 8 satellite imagery. The statistical indices such as R2, RMSE and MAE are computed between the algorithm derived value and the hydrographic chart sounding value. The result shows a good correlation between the algorithm derived value and hydrographic chart sounding value

Below the data range prediction of soft computing wave reflection of semicircular breakwater

Coastal defenses such as the breakwaters are important structures to maintain the navigation conditions in a harbor. The estimation of their hydrodynamic characteristics is conventionally done using physical models, subjecting to higher costs and prolonged procedures. Soft computing methods prove to be useful tools, in cases where the data availability from physical models is limited. The present paper employs adaptive neuro-fuzzy inference system (ANFIS) and artificial neural network (ANN) models to the data obtained from physical model studies to develop a novel methodology to predict the reflection coefficient (Kr) of seaside perforated semicircular breakwaters under low wave heights, for which no physical model data is available. The prediction was done using the input parameters viz., incident wave height (Hi), wave period (T), center-to-center spacing of perforations (S), diameter of perforations (D), radius of semicircular caisson (R), water depth (d), and semicircular breakwater structure height (hs). The study shows the prediction below the available data range of wave heights is possible by ANFIS and ANN models. However, the ANFIS performed better with R² = 0.9775 and the error reduced in comparison with the ANN model with R² = 0.9751. Study includes conventional data segregation and prediction using ANN and ANFIS

Physical model studies on the stability of emerged seaside perforated semicircular breakwaters

681-685Present study discusses experiments conducted in a two dimensional monochromatic wave flume to determine the critical (minimum) weight required to resist the sliding of an emerged seaside perforated semicircular breakwater model. It is observed from a detailed review that there is hardly any literature, stressing the critical weight determination for the sliding stability of this breakwater type. Hence, the present research was taken up to study the variations in the critical weight required for sliding stability with different wave and structural specific parameters. The variations were recorded graphically using non-dimensional parameters obtained from a dimensional analysis using Buckingham’s π theorem