Seasonal variation in longshore sediment transport rate and its impact on sediment budget along the wave-dominated Karna
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Seasonal variation in longshore sediment transport rate and its impact on sediment budget along the wave-dominated Karnataka coast, India ATEETH SHETTY and K S JAYAPPA* Department of Marine Geology, Mangalore University, Mangalagangothri, Mangaluru, Karnataka 574 199, India. *Corresponding author. e-mail: [email protected] MS received 1 May 2020; revised 29 August 2020; accepted 19 September 2020
The Karnataka coast is subjected to high wave activity during the southwest monsoon when most of the sandy beaches undergo erosion. Based on the littoral cell concept, the Karnataka coast is broadly divided into 14 major littoral cells and 26 stations are selected in the present study. WaveWatch III global wave model data at 0.5° interval were used to derive the nearshore wave characteristics from XBeach numerical model. The model results were validated with the measured wave rider buoy data of the Indian National Centre for Ocean Information Services. The beach orientation, nearshore slope, median sediment size, significant wave height, mean wave direction, and the peak wave period were used in the estimation of longshore sediment transport rate. The mean significant wave height along the Karnataka coast was about 0.86 m, wave direction was about 210° and peak wave period was about 13 sec. The wave height during southwest monsoon (June–September) was higher, post-monsoon (October–December) was moderate and pre-monsoon (January–May) was the calmest period. Direction of longshore sediment transport was southwards during pre- and post-monsoons when waves were from the south–southwest. Whereas, northwards during monsoon when the wave approach from west–southwest to west. The annual net longshore sediment transport rate estimated was about 0.659106 m3 towards the south and the sediment budget investigation depicts the loss of 0.0679106 m3 during the study period. Keywords. Littoral cell; wave characteristics; XBeach; sediment transport; sediment budget.
1. Introduction Knowledge of longshore sediment transport along a coast is vital for understanding the region’s coastal dynamics. Waves approach the shore obliquely and produce longshore currents that transport sediment alongshore. Numerous studies on longshore sediment transport have been published over the past decades (Komar 1998; Bayram et al. 2007;
Rao et al. 2009). Using various approaches, longshore studies have provided the foundation in understanding the longshore transport directions (Ashley et al. 1986; Esteves et al. 2009; Ari et al. 2013; Chowdhury and Behera 2017; Duc et al. 2019). However, most of the previous studies have been local in nature, conducted at site-speciBc beaches. Only a few of these studies extend beyond the local scale and fewer still compile previous
Supplementary materials pertaining to this article are available on the Journal of Earth Science Website (http://www.ias.ac.in/ Journals/Journal˙of˙Earth˙System˙Science).
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