APPLICATION OF THE THEORETICAL SOLUTION OF SHORELINE CHANGE TO KUJUKURI COAST AND EVALUATION OF COEFFICIENT OF LITTORAL DRIFT

The effects of the feedback between the changing coastal morphology and the wavefield on the generation and propagation of large scale (O(1-10 km)) shoreline sand waves is examined with a quasi-2D morphodynamic model. Traditional shoreline change models do not include this feedback and are only able to describe diffusion of shoreline sand waves and furthermore they are unable to describe migration. It is found with the present model that if there is a dominant littoral drift, the feedback causes downdrift migration of coastline features no matter if they grow or decay. Consistently with previous studies, simulations show that a rectilinear coastline becomes unstable and sand waves tend to grow spontaneously from random perturbations, if the wave incidence angle is larger then about 42o (θc) at the depth of closure (high angle wave instability). The initial wavelengths at which the sand waves develop are 2-3 km and this is similar to previous linear stability analysis. The implications of high angle wave instability for beach nourishments are investigated. The nourished shoreline retreats initially due to cross-shore transport because the nourished profile is steeper than the equilibrium profile. When a dominant littoral drift is present, the nourishment also migrates downdrift. If the wave angle at the depth of closure is below θc the alongshore transport contributes to the diffusion of the nourishment. However, if the angle is above θc (constant high angle wave conditions) the diffusion is reversed and the nourishment can trigger the formation of a shoreline sand wave train. Numerical experiments changing the proportion of ‘high angle waves’ and ‘low angle waves’ in the wave climate show that relatively small proportions of low angle waves slow down the growth of sand waves. These simulations with more realistic wave climates show shoreline sand waves that migrate downdrift maintaining more or less the same amplitude for years.

Download Full-text

Sediment transport and shoreline shifts in response to climate change at the tidal inlets of Chilika, India

Proceedings of the Institution of Mechanical Engineers Part M Journal of Engineering for the Maritime Environment ◽

10.1177/1475090217748755 ◽

2018 ◽

Vol 233 (1) ◽

pp. 372-387 ◽

Cited By ~ 1

Author(s):

B Gopikrishna ◽

MC Deo

Keyword(s):

Climate Change ◽

Sediment Transport ◽

Climate Model ◽

Regional Climate ◽

Shoreline Change ◽

Tidal Inlets ◽

Littoral Drift ◽

The Past ◽

Longshore Sediment Transport ◽

Other Information

The shoreline adjoining Chilika Lake, situated along India’s east coast, has multiple tidal inlets which connect the lake with Bay of Bengal. The shoreline behavior near such inlets is generally studied with the help of a suitable numerical model. Such models are run on the basis of historical data of waves and other information. However, the waves in future may show different strength and pattern than the past as a result of the climate change induced by global warming. It is thus necessary that the model input should correspond to future or projected data of wind and waves. In this work, we have used the wind information from a state-of-the-art regional climate model, CORDEX RegCM-4, of future 25 years in order to run a shoreline evolution model and have derived the longshore sediment transport rate as well as the shoreline change rate around Chilika inlets. These future values are compared with corresponding ones of the past 25 years. It is found that at the given location, mean wind might go up by 20%, and this could raise the mean significant wave height strongly by 32%. The direction and frequency of occurrence of waves would also change, and this in turn will cause an increase in the net littoral drift by 41% and net accumulated drift over the entire cross-shore width by 84%. Interestingly, the present site where accretion was prevalent in the past may see erosion in future at the rate of about 1 m per year.

Download Full-text

Implication of Shoreline and Nearshore Morphological Changes on Sediment Budget of Wave-Dominated Chennai Beach, India

10.21203/rs.3.rs-1045828/v1 ◽

2021 ◽

Author(s):

ATEETH SHETTY ◽

R. S. KANKARA ◽

DHANALAKSHMI S. ◽

BUCKLE S. ◽

SUBBURAJ S.

Keyword(s):

Morphological Changes ◽

Shoreline Change ◽

Sediment Budget ◽

Wave Direction ◽

Littoral Drift ◽

Monsoon Period ◽

Change Rate ◽

Southern Sector ◽

Longshore Sediment Transport ◽

Northern Sector

Abstract The study examines the shoreline (1990-2019) and nearshore morphological changes (seasonal) to understand the littoral drift and sediment budget variability. Shoreline change rate depicts erosion (-0.06 m/yr) in the northern sector and accretion (+0.12 m/yr) in the southern sector. Seasonal nearshore morphological changes from non-monsoon to monsoon period signifies net erosion (-1.8x10^4 m^3 ) in northern sector and net accretion (+2.5x10^4 m^3) in the southern sector. Although the lost sediment during monsoon is regained in non-monsoon period, the quantity of sediment gain is reduced in areas with human interventions. The results of the investigation depict the dominance of littoral drift towards north from February to October, when wave approach from east-southeast to south-southeast direction and southwards from November to January when the wave direction was from east-northeast to east-southeast. The net longshore sediment transport rate estimated during the study period was 2.6x10^5 m^3/year in the northern sector and 1.5x10^5 m^3/year in the southern sector with higher rate attributed to monsoon than the non-monsoon. Sediment budget results in deciphering the causes of erosion (-1.27×10^4 m^3/yr) in northern sector and accretion (3.91×10^4 m^3/yr) in southern sector in the wave-dominated Chennai beach.

Download Full-text

The Shoreline Deformation in Convex Beach due to Sea Level Rise

IOP Conference Series Earth and Environmental Science ◽

10.1088/1755-1315/925/1/012050 ◽

2021 ◽

Vol 925 (1) ◽

pp. 012050

Author(s):

Ariviana Vilda ◽

Lee Jung Lyul

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Wave Model ◽

Shoreline Change ◽

Global Scale ◽

Littoral Drift ◽

Annual Average ◽

Bruun Rule ◽

Depth Contour ◽

Extreme Scale

Abstract Sea level rise (SLR) is become more serious on a global scale and has become one of the main reasons causes shoreline changes, and erosion, even on an extreme scale can cause the sinking of coastal areas and islands. It was recorded that many big cities were damaged by SLR. The Bruun rule is the most widely used method for predicting the horizontal translation of the shoreline associated with a given rise in sea level. In this study, however, the change in the average shoreline at the convex beach, which is more vulnerable to erosion due to sea level rise, is investigated. The increase in water depth by sea level rise causes a change in the wave crestline, ultimately leading to a linearization of the shoreline. In general, it is assumed that the annual average shoreline is parallel to the annual mean wave crestline. Moreover, assuming that the equilibrium depth contour is formed according to the crestline, the retreat of the shoreline is predicted. The shoreline change is indirectly predicted through the wave crestline deformation obtained from a wave model and this method is applied to the convex beach. Our result showed that for a convex beach with a length of 1 km has open ends with free littoral drift at both ends, the sea level rise of 1 m cause the erosion of 10 m in the protruding area, and the sea level rise of 2 m causes erosion of 23 m. However, if the convex beach is blocked at both ends, sea level rise of 1 m causes the erosion of 6.3 m in the convex area, but the shoreline advance of 3.8 m at both ends, and if the sea level rise of 2 m occurs, the erosion of 14.3 m can occur in the convex area and shoreline advance of 8.6 m can occur at both ends.

Download Full-text

Littoral drift analysis based on long-term observation of mesotidal beach profile in Kuta Beach, Bali for coastal retreat assessment

IOP Conference Series Earth and Environmental Science ◽

10.1088/1755-1315/925/1/012040 ◽

2021 ◽

Vol 925 (1) ◽

pp. 012040

Author(s):

R. R. Rahmawati ◽

A. H.S. Putro ◽

J.L. Lee

Keyword(s):

Temporal Variability ◽

Shoreline Change ◽

Transport Processes ◽

Beach Erosion ◽

Observation Data ◽

Beach Profile ◽

Littoral Drift ◽

Shoreline Changes ◽

Coastal Retreat

Abstract The beach profile survey in the intertidal zone is crucial for a temporal variability study of shoreline and beach profile change for coastal management. The combination of numerical modelling and field data has proven to be successful in identifying the primary hydrodynamic and sediment transport processes such as littoral and cross-shore drift. Those parameters are relevant to the sandbar migration process and shoreline changes. The purpose of the present study is to analyse the littoral drift that caused temporal variability shoreline change in mesotidal beach for coastal retreat mitigation. Beach profile data of Kuta Beach was analyzed by 7 years of long-term field observation data both east monsoon and west monsoon situation. The shoreline definition used mean sea level (MSL)1.3 m and high water level (HWL) 2.6 m as reference. By using the MeEPASoL program as a graphical user interface program, shoreline changes converging to an equilibrium state can be simulated by taking into account the existing breakwater. Temporal shoreline position resulting from littoral drift and beach width change from its initial position is estimated for coastal erosion analysis. The result showed that dominantly, the littoral drift pattern moved from south to north. Furthermore, this study can be used in the process of identifying the primary hydrodynamic analysis in erosion disaster management as assessment of the beach erosion.

Download Full-text