Showing papers by "Vallam Sundar published in 2011"

Hydrodynamic Characteristics of Curved-Front Seawall Models Compared with Vertical Seawall under Regular Waves

Abstract: Seawalls remain one of the most widely adopted coastal-protection measure. The seawalls should be stable to ensure safety and optimally use the coastal space with a minimum or no waves overtopping but still keeping the crest elevation low. This may possibly be achieved by reshaping the front of the structure in such a way that it offers maximum resistance to the flow or enhances the dissipation of incident wave energy. With this as the background, an experimental study measuring run-up and overtopping of three different types of curved-front face seawall models, as well as the dynamic pressures exerted on each of them, was carried out. The measured parameters for the three types of seawalls are compared with that for a vertical seawall. All the tests were carried out with the models rigidly fixed over a bed slope of 1 in 30 in a wave flume and subjected to the action of regular waves. The details of the test facility, models, experimental program, results, and analysis are presented and discussed...

Effect of vegetation on run-up and wall pressures due to cnoidal waves

Abstract: A comprehensive experimental investigation was carried out to understand the effect of vegetation in attenuating run-up over a plane slope of 1 : 30 due to the propagation of cnoidal waves. Two different types of vegetation configurations, namely tandem and staggered, are considered. Dynamic pressures exerted along a vertical wall fronted by these two vegetation types were measured, and the typical variation of dimensionless peak pressures for different relative depths of submergence of the pressure ports is reported as a function of dimensionless parameters involving the vegetation and wave characteristics. Further, typical results on the variation of the dimensionless peak run-up versus the surf similarity parameter only for the staggered configuration are also herein reported. Finally, the percentage reduction in wave run-up and pressures on the wall due to the presence of wall fronted by vegetation are reported.

Numerical Model Studies on the Effect of Breakwaters on Coastal Processes — A Case Study along a Stretch of the Kerala Coast, India

Abstract: The Kayamkulam-Arattupuzha coastal stretch which forms part of the Kayamkulam - Thottapally (Quilon-Cochin) sector of the Kerala coast of India has been an eroding coastline for the past two to three decades. From 2000 to 2007 there has been a drastic increase in the erosion particularly around the inlet. Coincidentally, during the same period, two long breakwaters were constructed for the formation of the Kayamkulam fishing harbour. A critical analysis of the field data clearly indicates that the morphological changes are directly due to the construction of breakwaters. This paper reports the application of numerical models as an effective tool to study the coastal dynamics of the area and also to quantify and assess the shoreline changes for predicting the shoreline evolution pattern over a period of time. The Spectral Wave (SW) and Hydrodynamic Flow Model (FM) of the MIKE 21 modeling system (DHI) have been used for modeling the coastal dynamics, whereas, the studies on the shoreline change were carried...

Effect of the Tidal Currents at the Amphidromes on the Characteristics of an N-Wave-Type Tsunami

Abstract: The disturbance due to a tsunami is always coupled with permanent harmonic ocean tides. The tsunami based on its time of occurrence will combine with a particular tidal phase. Thus, a coast will experience a modified water level due to a high- or low-tide situation. On the other hand, the tidal current at the amphidromes may act as an attenuator or amplifier of the tsunami prior to its arrival at the shore. A one-dimensional numerical study has been carried out to demonstrate the effect of the amphidromic current on tsunami characteristics. A realistic N-wave profile of the initial perturbation has been considered for the initiation of a tsunami. The interaction of the amphidromic current with the phase velocity of an N-wave-type tsunami and the subsequent run-up along the shore has been investigated in this paper.

Numerical Modelling and Measurement of Sediment Transport and Beach Profile Changes along Southwest Coast of India

Abstract: In order to have an understanding of the coastal processes along the southwest coast of India (8°4′ N, 77° 33′ E to 8°13′ N, 77°14′ E), a data set available for the changes in beach width for a period of 5 years (1993–1998) over a length of about 50 km was categorized and analysed in relation to the seasons. Since the study area is densely populated and was also affected partially by the great Indian Ocean tsunami, a fresh measurement campaign of beach profile changes up to a water depth of 6 m at four different locations along the coast was carried out. These measurements have been adopted to validate a finite difference–based numerical model that employs the empirical formulation of Larson and Kraus (1989) for the prediction of beach profile changes. We simulated the offshore wave climate from National Centre for Environmental Prediction wind data using the Wave Analysis Model (WAM), whereas the nearshore wave climate was derived by adopting the MIKE21 Parabolic Mild Slope module. Results compa...

Simulation of shoreline evolution and estimation of alongshore sediment transport

Abstract: The maritime state of Tamilnadu located along the south east coast of India has a coastline of length of about 950 km orienting in the east and west coast. The coast has undergone the catastrophic effect of Tsunami of 2004 and protection measures in the form of groins were completed. In order to assess the beach formations it is necessary to have an understanding of sediment transport pattern along the tip of India peninsula. Measurement of the shoreline changes adjacent to shore connected structures were done in 2007 and satellite imageries were also adopted to assess the direction of littoral drift. A numerical model was formulated and was used for the prediction of the observed shoreline changes adopting the generated shore wave climate generated. Based on the predictions the along shore sediment transport rates were estimated to be 82000 to 40000 m 3 directed towards north and west directions respectively

Role of Vegetal Configuration on the Pressures Due to Cnoidal Waves on a Wall

Abstract: The dynamic pressures exerted on a vertical wall due to cnoidal waves have been investigated in presence and absence of model vegetation on its seaside. The pressures were measured at 3 different elevations along the wall. Tests were conducted with waves of constant height of 0.11m, with its period was varying between 5 and 20secs, thus covering a wide range of Ursell parameter varying between 18 and 700. The model vegetation was positioned adjacent to the wall on its seaside. All the vegetal characteristics including their rigidity are carefully modelled. The peak pressures (pmax) were extracted from the measured time series and are presented in a dimensionless form as a function of parameters governing the characteristics of waves and plantation. Two types of configurations of the green belt with the individual stems of vegetation fixed in tandem and staggered arrangement were considered for the tests. The study indicates that the staggered arrangement of plantation is more effective in attenuating the ...