ESTIMATION OF SHORELINE CHANGES OF THE CAI RIVER ESTUARY IN VIET NAM

THANH LUAN NGUYEN1*), THANH TUNG TRAN2), HOANG SON NGUYEN3),
VAN VAN THAN4) and YVES LACROIX5)

1*) Vietnam Key Laboratory of River and Coastal Engineering (KLORCE)
within Vietnam Academy for Water Resources (VAWR)
No 1, 165 Lane, Chua Boc - Dong Da, Ha Noi, Viet Nam
corresponding author to provide phone: +84(43)8521624; e-mail: thanhluance@gmail.com
2) Faculty of Marine and Coastal Engineering, TLU, Hanoi, Vietnam
175 Tay Son, Dong Da, Ha Noi, Viet Nam
e-mail: tunghwru@gmail.com
3) Faculty of Hydrology and Water Resources, TLU, Hanoi, Vietnam
175 Tay Son, Dong Da, Ha Noi, Viet Nam
e-mail: hoangson38v@gmail.com
4) Laboratory LATP, AMU and Faculty of Civil Engineering, TLU, Hanoi, Vietnam
39, rue F. Joliot Curie, 13453 Marseille Cedex 13, France
e-mail: thanvanvan@tlu.edu.vn
5) SEATECH, UTLN and MEMOCS, Università Degli Studi dell’Aquila, Italy
avenue G. Pompidou, 83162 La Valette du Var, France
e-mail: yves.lacroix@univ-tln.fr

Abstract

The Nha Trang Bay is one of the 29th most beautiful bays in the world, has been the centre of tourism and service of the Khanh Hoa province with quick growth in particular and the South Central region of Vietnam in general. Beside the development of infrastructure, urban, activities of people, impact of climate change, etc.,… they have made estuaries and coastal evolution more complicated. This paper presents accretion, erosion patterns at estuaries and coastal of Nha Trang bay by space and time scale with remote sensing technology and GIS. With a series of Landsat from 1999 to 2013, we give analysis results to calculate specifically shoreline changes. The sand dunes of the Northern and Southern coasts fluctuate, causing the expansion or the contraction of the width of the estuary. The study results showed that the Northern sand dune is tending to erode; the Southern one presents alternating periods of erosion and deposition that are seasonal, reported in recent years. The study results are the basis for scientist, administrator to find out surmounted methods, orienting coastal protection strategy, master plan Nha Trang coastal structure as Khanh Hoa province.

Keywords: DSAS, remote sensing, Nha Trang bay, estuary, erosion, accretion.

1.    INTRODUCTION

Nha Trang beach stretches from Bai Tien to the Lo river with a coastline (including the islands) at least 103 km from the Hon Dung island. Hon Lon island (Hon Tre) is the largest island, located on the eastern bay (Fig. 1). Southeastern bay is some small scattered islands forming the eastern and southeastern belt breakwater (a total of 19 islands). This bay has a length of about16 km (parallel along the shore) and width approximately 13 km (perpendicular to the shore). It has two estuaries: a main northeastern estuary and a smaller southeast estuary. The main source of freshwater flowing into the bay comes from the Cai river in Nha Trang. Dinh river (Ninh Hoa) impacts only in the Nha Phu lagoon; Tac river effects just south of the bay (Bui, 2002).

Determining the cause of coastal evolution (erosion and deposition) are very important for both scientific research as well as in practice. However, this is a very complex problem concerning many fields of study, even different concepts. For fully assessing the dynamics in the estuary coast of Nha Trang Bay, it is necessary to have an in-depth study with the appropriate research methodology and long enough period of time. Within the scope of this paper, the authors use the method of remote sensing image analysis over the multiple years, with parameters set as seasonal error, tidal fluctuation error, digitizing error, pixel error, and rectification error (Fletcher et al., 2011; Romine & Fletcher, 2012). The shoreline changes were assessed by using DSAS tools (Thieler et al., 2009).

Details see full paper at here

Vietnam-Japan Workshop on Estuaries, Coasts and Rivers 2015

September 7^nd -8^rd, Hoi An, Vietnam