DSpace at VNU: Analysis of sediment distribution and transport for mitigation of sand deposition hazard in Tam Quan estuary, Vietnam

DSpace at VNU: Analysis of sediment distribution and transport for mitigation of sand deposition hazard in Tam Quan estu...

Environ Earth Sci (2016) 75:741 DOI 10.1007/s12665-016-5560-2 ORIGINAL ARTICLE Analysis of sediment distribution and transport for mitigation of sand deposition hazard in Tam Quan estuary, Vietnam Do Minh Duc1 • Dinh Xuan Thanh1 • Dinh Thi Quynh1 • Patrick McLaren2 Received: November 2015 / Accepted: 11 March 2016 Ó Springer-Verlag Berlin Heidelberg 2016 Abstract Tam Quan estuary in the Binh Dinh Province of Vietnam provides shelter for about 2000 boats Recently, erosion and accretion associated with the mouth of the estuary have badly affected marine transportation and economic development An 850-m-long jetty was constructed to mitigate the hazard However, sand deposition still continues to be an ongoing problem This paper aimed to assess the reasons for sand deposition in the estuary based on sediment distributions and transport pathways Following an investigation of topography, geological and hydrodynamic conditions, and sediment characteristics, an analysis of sediment transport trends was undertaken Results show that medium sand is distributed along the coast from the shoreline to 2.5 m water depth Fine sands are found in deeper areas of 10–13 m where there are also medium sand deposits thought to be of ancient origin Sand deposition has intensively occurred in the estuary due to a dominant north-to-south longshore sediment transport regime Sediment from this regime is presently trapped by the jetty and deposited in the navigation channel As a solution, it is suggested that a properly designed jetty stemming from the headland on the north side of the estuary could effectively control the patterns of sediment transport enabling the sand to bypass the entrance, thereby avoiding entrapment inside its mouth & Do Minh Duc ducdm@vnu.edu.vn Faculty of Geology, VNU University of Science, Vietnam National University, Hanoi, 334 Nguyen Trai, Thanh Xuan, Hanoi, Vietnam SedTrend Analysis Limited, 7236 Peden Lane, Brentwood Bay, BC V8M1C5, Canada Keywords Estuary Á Sediment Á Sand deposition Á Navigation channel Á Sediment trend analysis Introduction There has been extensive research worldwide on sediment distribution and transport in estuaries However, much of this work has focused on coastal plain estuaries Information on confined estuaries with steep slopes and floored by sand- and gravel-sized sediments is rather limited (Portela 2008) Moreover, morphologic changes in estuaries are occurring more seriously due to human and climate change impacts (Duc et al 2012; Zhang et al 2014; Chalov et al 2015; He et al 2015) which may lead to deposition and/or erosion hazards An early recognition of grain-size trends and sediment transport (McCave 1978) showed how grain size along a beach can coarsen in the direction of net wave-driven transport The cause was ascribed to progressive winnowing out of the finer fraction and its dispersal offshore by tidal currents Other situations without strong tidal currents may allow the winnowed fines to be reintroduced to the beach further down drift and yield a fining trend The concepts to predict the relative changes that will occur in particle size distributions of sediments through erosion, transport, and deposition were first presented in McLaren (1981) followed by a more complete mathematical theory (McLaren and Bowles 1985) On the basis of their theory, several methods to carry out sediment trend analysis (STA) have been developed The McLaren and Bowles approach is one dimensional, whereby the changes in grain-size distributions along individual sample sequences are tested for validity with the Z score statistic to determine the preferred transport direction However, following 123 741 Page of 13 numerous testing of individual sample lines, a two dimensional transport pattern is achieved A practical assessment of this approach is discussed in Hughes (2005) Gao and Collins (1991, 1992) and Gao (1996) proposed a two-dimensional vector approach to determine trends, some elements of which were revised by Chang et al (2001) A different vector approach altogether was produced by Le Roux (1994) and Le Roux et al (2002) A summary of the various techniques is provided in Rios et al (2003) and Poizot et al (2008) The STA technique has still several uncertainties associated with the methodology including transport model assumptions, sample spacing, bias of the mean, variance and skewness of grain sizes in the log-normal distribution, random environmental and measurement uncertainties A number of authors found their results to agree, either in whole or in part, with a variety of other evidence including direct measurements of processes, observations of bedform orientations and application of numerical modelling (Livingstone 1989; Lanckneus et al 1992; Van de Kreeke and Robaczewska 1993; Gao and Collins 1994; Gao et al 1994; Aldridge 1997; Bergemann et al 1998; Van Der Wal 2000; Mallet et al 2000; Duck et al 2001) However, some authors found no agreement between the STA and outside evidence (Flemming 1988; Masselink 1992; Guillen and Jimenez 1995) STA was accepted as a tool for investigation of coastal projects of US Army Corp of Engineers (Hughes 2005) STA was used to indicate the sediment pathways inside a lagoon which can be related to the sediments sources, wind-related water circulation and wind directions (Avramidis et al 2008) STA in the integration of acoustic data leads to a better understanding of the sedimentary, morphological and biological processes in a shallow lagoon in different spatial and temporal scales (Papatheodorou et al 2012) STA was also successfully applied for a study of sediment pollution (McLaren and Singer 2008), coastal change and sedimentation in estuaries (Van de Kreeke and Robaczewska 1993; Bergemann et al 1998; McLaren and Beveridge 2006; McLaren et al 2007; McLaren and Braid 2009; McLaren and Teear 2014) The estuaries on the central coast of Vietnam, situated in the south-west sector of the Gulf of Tonkin and the East Vietnam Sea (Fig 1), are typical examples of such systems In recent years, navigation channels in the estuaries of the central part of Vietnam have been facing severe sand deposition Fishing boats are frequently unable to go in or out of their harbours, resulting in a serious reduction in the transport of aquacultural products Some of the most typical estuaries are My A (Quang Ngai Province), Da Rang, Da Dien (Phu Yen Province), and Tam Quan and Lai Giang (Binh Dinh Province) (Fig 2) As a contribution to understand and solve this problem, this paper aimed to 123 Environ Earth Sci (2016) 75:741 clarify the reasons for sand deposition in Tam Quan estuary based on the analysis of surface sediment distributions and transport and then propose suitable countermeasures Study area In the central part of Vietnam, high rainfall in the steep hinterland results in an abundance of rivers and their associated estuarine lagoons at the coast Rivers with large basin areas, usually larger than 500 km2, maintain open inlets during the whole year Because river discharge in the central coast is strongly seasonal, river mouths and tidal inlets tend to adjust to an equilibrium morphology associated with low flow conditions during the relatively long dry period The morphology of estuaries formed under normal conditions may be altered dramatically by increased river discharges (Tung 2011) The sediment concentrations in the main rivers are usually around 50–150 mg/l, but during floods the concentrations are greatly increased (Eriksson and Persson 2014) This type of estuary with significant influence of river flood flows is dominant However, due to construction of dams for agriculture, water discharge of some small rivers is strongly interrupted and marine and coastal dynamics are more important than river dynamics at the river mouths The coast is predominantly sandy as a result of alluvial accumulation, which nourishes the beaches and sandy barriers that form across estuary mouths and tidal inlets (Tung 2011) The 100-m contour line is just about 10 km from the shoreline Tam Quan estuary is located in Hoai Nhon District, Binh Dinh Province This is the centre of coastal economic development of the Binh Dinh Province where there is a harbour frequently containing more than 2000 fishing boats The navigation channel into Tam Quan estuary is about 150 m wide and 850 m long Faced with the adverse impacts of sand deposition, the local government, between 1998 and 2001, constructed a 400-m-long jetty extending seaward from the northern tip of a barrier beach on the south side of the harbour entrance However, the navigation channel continued to infill with sand until 2004 after which, between 2006 and 2008, the jetty was elongated a further 450 m A technical explanation for its expansion does not, apparently, exist, and sand deposition has continued to be a problem since 2010 (Fig 3) with the navigation channel requiring periodic dredging between September 2012 and March 2014 The dredged sand amounting to 61,600 m3 was used as filling materials for local construction Today, the sand deposition continues to be a problem and dredging is frequently required to maintain the navigation channel of Tam Quan estuary The area surrounding the Tam Quan estuary is underlain by a variety of igneous and metamorphic rocks that include Environ Earth Sci (2016) 75:741 Page of 13 741 Fig River system and tidal inlets in the central coast of Vietnam the Kim Son Formation and the Phu My, Ben Giang and Hai Van complexes (Fig 4) Quaternary marine sediments are found mainly in the north as well as in small areas to the south of the estuary which appear as low relief within the confines of the valley Also on the south side, there are riverine–marine–swampy sediments River sediments are characterized by sand and gravel as well as cobbles containing a large variety of lithologies Coastal dunes, 10–20 m high, 0.2–1.5 km wide and 2–5 km long, are found along large portions of the coastline Waves are subject to seasonal changes with north-east waves dominant from October to April During June to September, south and east waves dominate whereas May is a transitional season during which time waves are low and their directions irregular Average wave heights are from 1.2 to 1.7 m with maximum heights reaching 12 m during typhoon conditions Annually, south-east, south and east waves occur 47, 24 and 13 %, of the time, respectively (Table 1) For about 60 % of the time, dominant wave heights range from 0.51 to 1.50 m; larger waves (1.51–2.50 m) occur 20 % of the time 123 741 Page of 13 Environ Earth Sci (2016) 75:741 Fig Tidal inlets characterized by severe sand deposition in the central coast of Vietnam Tides are irregular and diurnal Tides more than 155 cm occur only % of the time Long-term maximum spring and neap tide ranges are 107 and -93 cm, respectively Storm surges have been recorded at a maximum of 1.7 m Tam Quan estuary receives water from only three small streams, and turbidity measurements show that sediment input from these rivers is negligible Data of bottom currents (about m above the sea floor) was retrieved during a week in two periods of October 2012 and June 2013, respectively (Fig 5) The currents were monitored at two stations (Fig 6) which were set up at m water depth The results show a dominant direction of currents from north to south in October Maximum velocity was recorded at about 27 cm/s with an average of 13 cm/s In June, current directions are mixed between north–south, south–north and east–west Velocities are cm/s on average However, east–west current velocities reached 30–37 cm/s for some short times due to strong south-west wind-induced waves Methods A total of 130 sediment grab samples were collected along the Tam Quan coastline to a depth of 20 m (Fig 6) Based on rectangular grid, samples were from 150 to 250 m apart and were positioned by GPS to an accuracy of ±5 m Grain-size distributions were obtained by sieving the sandy fraction (sieve sizes: 2, 1, 0.5, 0.35, 0.25, 0.18, 0.15, 0.125, 0.1, 0.074 and 0.063 mm, i.e -1.0, 0, 1.0, 1.51, 2, 2.47, 2.74, 3.0, 3.32, 3.76 and 4.0 u) and the grain-size 123 parameters of mean, sorting and skewness were calculated in u units (Folk 1966, 1980) The mineral composition was analysed by thin section using an optical microscope Representative portions of about 15 g from each sample were thoroughly washed several times with water followed by a bath of dilute hydrochloric and sulphuric acids to clean the grains of any limonite coating or stains After drying, the material was sieved through a half-millimetre sieve The portion of grains smaller than mm in size was separated by means of bromoform having a specific gravity of 2.83 After each process, the sands were weighed Permanent slides of the light and heavy portions of these sands were made for later microscopic determination using Canada balsam as the imbedding medium The mineral composition was estimated by using point counting McLaren and Bowles (1985) demonstrated that when two sediment samples (d1 and d2) are taken sequentially in a known transport direction (e.g from a river bed, where d1 is the up current sample and d2 is the down current sample), the sediment distribution of d2 may become finer (case B) or coarser (case C) than that of d1; if it becomes finer, the skewness of the distribution must become more negative Conversely, if d2 is coarser than d1, the skewness must become more positive The sorting becomes better (i.e the value for variance decreases) for both cases If either of these two trends is observed, sediment transport from d1 to d2 can be inferred If the trend is different from the two acceptable trends, the trend is unacceptable, and it cannot be supposed that transport between the two samples has Environ Earth Sci (2016) 75:741 Page of 13 741 Fig Sand deposition in navigation channel of Tam Quan estuary The area of severe sand deposition was about 150 m long and 100 m wide, which started from a point of 120 m from seaside head of the jetty in May 2010 The navigation channel was 50 m wide at the south side near the jetty; boats could go in and out during spring tide Sand deposition was then significantly enlarged and the navigation channel shifted to the north side near the rock mountain in February 2014; boats can also go in and out during spring tide taken place In the preceding example, where the transport direction is unequivocally known, d2(s) can be related to d1(s) by a function X(s), where s is the grain size The distribution of X(s) may be determined by: X(s) provides the statistical relationship between the two deposits, and its distribution defines the relative probability of each particular grain size being eroded, transported and deposited from d1 to d2 The shape of the X(s) distribution relative to the shapes of the d1(s) and d2(s) distributions d2 s ị ẳ d1 s Þ X ð s Þ 123 741 Page of 13 Environ Earth Sci (2016) 75:741 Fig Geological settings at Tam Quan estuary Table Frequency (%) of wave heights at the nearshore of Tam Quan estuary Wave height (m) N NE \0.25 0.00 0.13 0.38 0.16 0.26–0.5 0.07 1.28 2.65 1.95 0.51–1.5 1.26 18.86 9.24 5.6 1.51–2.5 0.93 16.41 0.33 0.11 1.29 0.52 2.51–3.5 0.43 7.56 0.03 0.01 0.03 0.02 [3.5 0.34 3.37 0.02 0.00 0.00 0.00 0.00 0.01 Total 3.03 47.61 12.65 7.83 24.19 4.10 0.39 0.18 determines the behaviour (stability) of the sediments There are five defined categories for behaviour: (1) net erosion, (2) net accretion, (3) equilibrium, (4) total deposition type and (5) total deposition type (McLaren and Singer 2008; McLaren and Braid 2009) There is now a large body of literature that uses or discusses sediment trend analysis (STA) (e.g Gao and Collins 1991, 1992; Gao 1996; Chang et al 2001; Le Roux 1994; Le Roux et al 2002; Hughes 2005; He´quette et al 2008; Poizot et al 2008; Duc et al 2012; McLaren 2014; McLaren and Teear 2014) As a result, a number of methods have been developed to apply the theory to derive transport pathways For this paper, the STA was carried out following the descriptions provided in McLaren and Beveridge (2006) and McLaren et al (2007) 123 E SE S SW W NW Sub-total 0.04 0.00 0.00 0.01 0.71 1.60 0.10 0.39 0.03 8.08 21.23 3.46 0.00 0.04 59.69 0.00 0.06 19.65 0.00 0.03 8.11 3.76 100 Results Sediment characteristics Based on their characteristics (Table 2) and spatial distribution, sediments were classified into four types which include nearshore coarse-medium sand, nearshore fine sand, offshore medium sand and offshore fine sand (Figs 7, 8, 9) These are described as follows Nearshore coarse-medium sand This sediment type extends from the coast line to water depths of 2.5–3.0 m which is at a distance of about 200 m from the shoreline Sediments have mean grain diameters Environ Earth Sci (2016) 75:741 Page of 13 741 Fig Characteristics of currents at north shore of Tam Quan estuary (a from 30 September to October 2012; b from June to June 2013) Fig Sediment sampling locations 123 741 Page of 13 Environ Earth Sci (2016) 75:741 Table Characteristics of surface sediments in at the nearshore of Tam Quan estuary Sediment Nearshore coarsemedium sand Grain-size parameters (u) Mineral composition (%) Mean So Sk Quartz Felspar Kali Biotite Muscovite Plagioclaz Heavy mineral 0.5–1.8 (1.2)a 0.4–1.1 (0.8) -0.1 to 0.5 (0.1) 70 15 Nearshore fine sand 2.4–3.3 (2.8) 0.5–0.9 (0.6) -0.4 to 0.1 (-0.3) 75 10 4 Offshore medium sand 1.1–1.9 (1.7) 0.7–0.9 (0.8) -0.1 to 0.3 (0.1) 80 12 Offshore fine sand 2.1–3.1 (2.5) 0.6–1.3 (0.7) -0.5 to 0.1 (-0.1) 80 12 a 0.5–1.8 (1.2): Min–Max (average) Fig Sediment distribution at Tam Quan estuary of 0.5–2.6 u, average value of 1.2 u Sorting coefficients are from 0.4 u (well sorted) to 1.1 u (poorly sorted), average value of 0.8 u (moderately sorted) Similarly, skewness varies from coarse skewed (-0.1 u) to strongly fine skewed (0.5 u) The average value is near symmetrical (0.1 u) These characteristics suggest an environment of highly variable hydrodynamic conditions, which is mainly controlled by the formation and migration of rip currents, especially during time period of north-east waves (from October to April next year) (Trinh et al 2011; Tung 2011) 123 Nearshore fine sand Offshore from the nearshore coarse-medium sand, this sediment type ranges from 2.5–3.0 to 10–12 m water depths to a distance of 200–800 m from the shoreline Mean grain diameters vary from 2.4 to 3.3 u, with an average value of 2.8 u Sorting coefficients are in a narrow range from 0.5 u (moderately well sorted) to 0.9 u (moderately sorted), average value of 0.6 u (moderately well sorted) Skewness varies from strongly coarse skewed (-0.4 u) to near symmetrical (0.1 u), average value of -0.3 u (strongly coarse skewed) Environ Earth Sci (2016) 75:741 Page of 13 741 Fig Distribution of modern sediment grain-size mean value at the nearshore zone Fig Distribution of modern sediment sorting value at the nearshore zone Offshore medium sands Offshore fine sands Found in depths ranging from 10–12 to 20 m, these sediments have mean grain diameters of 1.1–1.9 u, with an average value of 1.7 u Sorting coefficients are slightly varied from 0.7 to 0.9 u (moderately sorted) Skewness changes from coarse skewed (-0.1 u) to fine skewed (0.3 u) The average value is near symmetrical (0.1 u) These sediments have mean grain diameters varying from 2.1 to 3.1 u, average value of 2.5 u Sorting coefficients are in a large range from 0.6 u (moderately well sorted) to 1.3 u (poorly sorted), average value of 0.7 u (moderately well sorted) Skewness varies from strongly coarse skewed (-0.5 u) to near symmetrical (0.1 u), average value of 123 741 Page 10 of 13 -0.1 u (coarse skewed) Like the offshore medium sands, the offshore fine sands are also found from 10 to 12 m to m of water and both sediment types have a similar colour to the nearshore sands, but their grain-size characteristics fall into much narrower ranges In terms of mineral composition, sediments are quite homogenous (Table 2) Quartz dominates with contents of 75–80 % followed by kali feldspar which ranges from 10 to 15 % Other minerals include small amounts (2–6 %) of biotite, muscovite, plagioclase and heavy minerals These findings suggest that the hydrodynamic conditions not lead to any significant differentiation in mineral compositions and that all the sediment types are likely derived from a similar source Sediment transport at the nearshore zone of Tam Quan estuary Environ Earth Sci (2016) 75:741 • • The results of the STA, as shown Fig 10, are listed as follows: • Sediments are not transported from the coastline to shallow water (up to about 2.5 m water depth) on either side of the Tam Quan estuary This supports the concept that both northern and southern parts of the beach are relatively stable and that the predominant wave direction is almost perpendicular to the shoreline An exception occurs in a short segment of the Tam Quan north shore (Fig 8), where the coast is known to have eroded in recent years Fig 10 Transport of modern sediments at the nearshore zone 123 • • The dominant transport behaviour of sediment in the north part of Tam Quan estuary is net accretion at water depths of 2.5–10 m It shows relative significant strength of southward sediment transport which matches well with the dominance of north–south bottom currents in the area Moreover, the net accretion indicates a likely increase of available sediments for transporting southwards Around the Truong Xuan headland, this mode was also found at the water depths of 5–10 m but changes to net erosion at shallower water depths of 2–5 m Change in shoreline orientation at the headlands leads to the formation of a high wave energy surf zone in the shallow water Sediment samples were unable to be collected in the shallow water surrounding the rocky headland precluding the determination of the transport regime at 0–2 m water depths in this area Around the Tam Quan estuary, sediments are transported past the Truong Xuan headland generally as net accretion but with occasional sample sequences showing net erosion or equilibrium Sediment trends were undefined in much of the navigation channel, most likely the result of recent dredging in the area Sediments are transported along the south side of the jetty in equilibrium and net accretion Near jetty’s head, sediments not show any transport In the south part of the estuary, sediment trends were not defined at the water depths of 0–5 m near the jetty (300–1000 m southwards) In the other parts (from to Environ Earth Sci (2016) 75:741 10 m water depths), sediment trends are net erosion and then change to equilibrium further South Discussion Spatial distribution of sediments Pale yellow medium sands are found along the coast from the shoreline to 2.5 m water depth Fine sands with a light grey colour occur in the deeper areas which are up to 11 m in the north, 13 m opposite the mouth of the estuary and 10 m to its south This spatial distribution was formed as a result of current hydrodynamic conditions Medium sands exist in the high wave energy characterized by the surf zone, and fine sands are more associated with the wave propagating zone Due to the impact of the jetty, fine sand has accumulated on shoreline at the south side covering a linear distance of 300 m (Fig 5) In addition, a small emerged bar of medium sand with better sorting coefficients was formed at the depth of 1.8–2.0 m (Fig 7) In the deeper area, dark yellow medium sands exposed The existence of these coarse sediments suggests that they are not formed by current hydrodynamic conditions The shoreline of Vietnam in general and its central part in particular has altered significantly during the Holocene period as a result of sea level change (Korotky et al 1995; Nguyen et al 2000; Funabiki et al 2007; Tan et al 2014) causing the boundary between modern shoreline sediments and the ancient deposits found in the deeper water (Fig 5) Such a boundary has been observed before in depths of about 30 m in the vicinity of the Red River delta (Duc et al 2007, 2012) and 15–20 m adjacent to the central part of the coast (Korotky et al 1995) These studies, based on sediment distribution, colour and grain size, suggest that the boundary separates modern (late Holocene) sediments and ancient (early Holocene) sediments However, further work to include radioactive dating and geochemical analyses will be required to verify the ages of the two sediment types Reasons of sand deposition As mentioned above, both northern and southern parts of the beach are relatively stable and the predominant wave direction is almost perpendicular to the shoreline The orientations of both shorelines are almost the same at about 333°; however, the direction of shoreline just north of the estuary is significantly greater (about 351°) (Fig 10) This shoreline configuration results in southward transport and sediment, as shown in Fig 10, reaches the Tam Quan estuary as it passes around the small headland Sediments are deposited in two different areas One is after the north Page 11 of 13 741 headland and another is close to the south jetty The much shallower bottom behind the headland causes a significant dissipation of wave energy leading to net accretion in this area Sand then bypasses the navigation channel to accumulate on its other side Trends of the bypassing cannot be observed in the analysis due to frequent dredging of the channel However, net erosion in the nearby zone of the jetty shows evidence of sediment transport southward to the jetty The head of the jetty, installed in m of water, serves as a sediment trap resulting in severe sand deposition in the navigation channel of the Tam Quan estuary In the long term, additional sand deposition in the channel can be transported from the south towards the head of the jetty Impacts of south jetty Prior to the jetty, sediment bypassed the estuary’s entrance via the sand bar in front of the river mouth (Trinh et al 2011) Even after its construction, the initial length of the jetty was insufficient to result in the deposition that is occurring today At Tam Quan estuary, before the jetty extension, it was likely that sand naturally bypassed the estuary entrance However, after its extension, all sediment transported from the north became trapped by the jetty and deposited in the channel as shown in Fig The southern shoreline close to the base of the jetty also advanced a little due to incoming waves that could now become diffracted by its presence Proposal of engineering measures to prevent sand deposition in channel To prevent sedimentation in the channel, sediment transport from north to south past the small headland requires controlling A properly designed jetty at the north headland can effectively control this sediment movement There are two ways to prevent sedimentation in the channel which are illustrated in Fig 11 The first is to trap sediment transported to the south before entering the channel (Fig 11a) The other is to encourage the transport of sediment to bypass the estuary’s mouth as it did in the past (Fig 11b) The precise design and locations of the two proposed jetty structures will require a more complete investigation of the characteristics of sediment movement To maintain the fishery harbour in the Tam Quan estuary, it will be necessary to consider the location and shape of the north breakwater (ln), the length of the existing jetty (le) as well as the location and shape of the south breakwater (Fig 11) At this time, the length of the existing south jetty could possibly be shortened provided that it can be shown to prevent northward sediment transport caused by diffracted 123 741 Page 12 of 13 Environ Earth Sci (2016) 75:741 Fig 11 Control of sediment transport at Tam Quan estuary by jetty (a sand trap by straight upright jetty; b sand bypass by inclined jetty) waves around the newly constructed north jetty and the extreme waves caused by typhoons, although the probability of their occurrences will not be so high Conclusions Two types of sand deposits (modern and ancient) were defined in the offshore area of the Tam Quan estuary The boundary between the two is in 11 m water depth in the north, 13 m opposite the mouth and 10 m to the south of the estuary In addition, modern medium sand is distributed along the coast from the shoreline to 2.5 m water depth and finer sand is found in water depths of 2.5 to 10–13 m In the deeper area, ancient medium and fine sands are exposed Dominant longshore sediment transport is from north to south at the Tam Quan estuary Sediments are trapped by the present jetty and resulting in severe sand deposition in the navigation channel As a solution, a properly designed jetty at the north headland will effectively control this sediment movement by either trapping the sand or helping to ensure that the sand bypasses the estuary’s mouth as it did prior to the construction of present entrance jetty Acknowledgments This research is funded by the Vietnam National Foundation for Science and Technology Development (NAFOSTED) under Grant number 105.99-2012.14 References Aldridge JN (1997) Hydrodynamic model predictions of tidal asymmetry and observed sediment transport paths in Morecambe Bay Estuar Coast Shelf Sci 44:39–56 123 Avramidis P, Bouzos D, Antoniou V, Kontopoulos N (2008) Application of grain size trend analysis and spatio-temporal changes of sedimentation, as a tool for lagoon management Case study: the Kotychi lagoon (western Greece) Geol Carpath 59:261–268 Bergemann F, Lang G, Flugge G (1998) A particle method for sediment transport modeling in the Jade Estuary In: Spaulding ML, Blumberg AF (eds) Proceedings of the 5th international conference of estuarine and coastal modeling, Alexandria, VA Chalov SR, Jarsjoă J, Kasimov NS, Romanchenko AO, Pietron J, Thorslund J, Promakhova EV (2015) Spatio-temporal variation of sediment transport in the Selenga River Basin, Mongolia and Russia Environ Earth Sci 73(2):663–680 Chang YH, Scrimshaw MD, Lester JN (2001) A revised grain-size trend analysis program to define net sediment transport pathways Comput Geosci 27(1):109–114 Duc DM, Nhuan MT, Ngoi CV, Nghi T, Tien DM, van Weering TjCE, van den Bergh GD (2007) Sediment distribution and transport at the nearshore zone of the Red River delta, Northern Vietnam J Asian Earth Sci 29(4):565–588 Duc DM, Nhuan MT, Ngoi CV (2012) An analysis of coastal erosion in the tropical rapid accretion delta of the Red River, Vietnam J Asian Earth Sci 43:98–109 Duck RW, Rowan JS, Jenkins PA, Youngs I (2001) A multi-method study of bedload provenance and transport pathways in an estuarine channel Phys Chem Earth B 26(9):747–752 Eriksson EL, Persson MH (2014) Sediment transport and coastal evolution at Thuan An Inlet, Vietnam MSc Thesis, Lund University http://lup.lub.lu.se/luur/download?func=downloadFi le&recordOId=4393060&fileOId=4393063 Accessed 24 Feb 2016 Flemming BW (1988) Process and pattern of sediment mixing in a microtidal coastal lagoon along the westcoast of South Africa In: De Boer PL, Van Gelder A, Nio SD (eds) Tide-influenced sedimentary environments and facies D Reidel Publishing Company, Dordrecht, 275–288 Folk RL (1966) A review of grain-size parameters Sedimentology 6:73–93 Folk RL (1980) Petrology of sedimentary rocks Hemphill Publication Co., Austin, p 185 Environ Earth Sci (2016) 75:741 Funabiki A, Haruyama S, Quy NV, Hai PV, Thai DH (2007) Holocene delta plain development in the Song Hong (Red River) delta, Vietnam J Asian Earth Sci 30(3–4):518–529 Gao S (1996) A Fortran program for grain-size trend analysis to define net sediment transport pathways Comput Geosci 22(4):449–452 Gao S, Collins M (1991) A critique of the ‘‘McLaren method’’ for defining sediment transport paths J Sediment Petrol 61(1):143–146 Gao S, Collins M (1992) Net sediment transport patterns inferred from grain-size trends, based upon definition of ‘‘transport vectors’’ Sed Geol 80(1–2):47–60 Gao S, Collins M (1994) Analysis of grain size trends, for defining sediment transport pathways in marine environments J Coast Res 10(1):70–78 Gao S, Collins MB, Lanckneus J, De Moor G, Van Lancker V (1994) Grain size trends associated with net sediment transport patterns: an example from the Belgian continental shelf Mar Geol 121:171–185 Guillen J, Jimenez JA (1995) Processes behind the longshore variation of the sediment grain size in the Ebro Delta coast J Coast Res 11(1):205–218 He X, Wang YP, Zhu Q, Zhang Y, Zhang D, Zhang J, Yang Y, Gao J (2015) Simulation of sedimentary dynamics in a small-scale estuary: the role of human activities Environ Earth Sci 74(1):869–878 He´quette A, Hemdane Y, Anthony EJ (2008) Determination of sediment transport paths in macrotidal shoreface environments: a comparison of grain-size trend analysis with near-bed current measurements J Coast Res 24(3):695–707 Hughes SA (2005) Use of sediment trend analysis (STA) for coastal projects ERDC/CHL CHETN-VI-40 Vicksburg, MS: US Army Corps of Engineers, p 17 Korotky AM, Razjigaeva NG, Ganzey LA, Volkov VG, Grebennikova TA, Bazarova VB, Kovalukh NN (1995) Late Pleistocene–Holocene coastal development of islands off Vietnam J SE Asian Earth Sci 11(4):301–308 Lanckneus J, De Moor G, De Schaepmeester G (1992) Residual sediment transport directions on a tidal sand bank: Comparison of the ‘McLaren model’ with bedform analysis Bulletin de la Societe belge d’Etudes Geographique—SOBEG 2:425–446 Le Roux JP (1994) An alternative approach to the identification of net sediment transport paths based on grain-size trends Sed Geol 94(1–2):97–107 Le Roux JP, O’Brian RD, Rios F, Cisternas M (2002) Analysis of sediment transport paths using grain-size parameters Comput Geosci 28(5):717–721 Livingstone I (1989) Temporal trends in grain-size measures on a linear sand dune Sedimentology 26:1017–1022 Mallet C, Howa HL, Garlan T, Sottolichio A, Le Hir P, Michel D (2000) Utilisation of numerical and statistical techniques to describe sedimentary circulation patterns in the mouth of the Gironde estuary Earth Planet Sci 331:1–7 Masselink G (1992) Longshore variation of grain size distribution along the coast of the Rhone Delta, Southern France: A test of the ‘McLaren model’ J Coast Res 8(2):286–291 Page 13 of 13 741 McCave IN (1978) Grain size trends and transport along beaches: an example from eastern England Mar Geol 28:43–51 McLaren P (1981) An interpretation of trends in grain-size measurements J Sediment Petrol 51:611–624 McLaren P (2014) Sediment trend analysis (STA): kinematic vs dynamic modeling J Coasta l Res 30(3):429–438 McLaren P, Beveridge P (2006) Sediment trend analysis of the Hylebos Waterway: implications for liability allocations Integr Environ Assess Manag 2(3):262–272 McLaren P, Bowles D (1985) The effects of sediment transport on grain-size implications of the ‘Red Clay’ (North China) as evidenced by grain-size distribution J Quatern Sci 16(1):89–97 McLaren P, Braid M (2009) Sediment trend analysis in support of unexploded explosive ordnance (UXO) risk assessment J Am Soc Test Mater Int 6(7):1–20 McLaren P, Singer J (2008) Sediment transport and contaminant behavior in the Buffalo River, New York: implications for river management J Coast Res 24(4):954–968 McLaren P, Teear G (2014) A sediment trend analysis (STA) in support of dredged material management in Lyttelton Harbour, Christchurch, New Zealand J Coast Res 30(3):438–447 McLaren P, Hill SH, Bowles D (2007) Deriving transport pathways in a sediment trend analysis (STA) Sed Geol 202(3):489–498 Nguyen VL, Ta TKO, Tateishi M (2000) Late Holocene depositional environments and coastal evolution of the Mekong River Delta, Southern Vietnam J Asian Earth Sci 18(4):427–439 Papatheodorou G, Avramidis P, Fakiris E, Christodoulou D, Kontopoulos N (2012) Bed diversity in the shallow water environment of Pappas Lagoon in Greece Int J Sedim Res 27:1–17 Poizot P, Mear Y, Biscara L (2008) Sediment trend analysis through the variation of granulometric parameters: a review of theories and applications Earth Sci Rev 86(1–4):15–41 Portela LI (2008) Sediment transport and morphodynamics of the Douro River estuary Geo-Mar Lett 28:77–86 Rios F, Ulloa R, Cerrea ICS (2003) Determination of net sediment transport patterns in Lirquen Harbor, Chile through grain-size analysis: a test of methods Pesquisas em Geociencias 30(1):65–81 Tan MT, Dung LV, Bach LD, Bieu N, Nghi T, Long HV, Huong PV (2014) Pliocene-Quaternary evolution of the continental shelf of central Vietnam based on high resolution seismic data J Asian Earth Sci 79:529–539 Trinh LP, Long BH, Mau LD, Trung PB (2011) Typical hydrodynamic conditions causing erosion-accretion in the coast of Vietnam Southern Central part J Mar Sci Technol 11(3):15–30 (in Vietnamese) Tung TT (2011) Morphodynamics of seasonally closed coastal inlets at the Central coast of Vietnam PhD Disertation, Technische Universiteit Delft Van de Kreeke J, Robaczewska K (1993) Tide-induced residual transport of coarse sediment: application to the Ems Estuary Neth J Sea Res 31(3):209–220 Van Der Wal D (2000) Grain-size-selective aeolian sand transport on a nourished beach J Coast Res 16(3):896–908 Zhang X, Dai Z, Chu A, Du J (2014) Impacts of relative sea level rise on the shoreface deposition, Shuidong Bay, South China Environ Earth Sci 71(8):3503–3515 123 ... head of the jetty, installed in m of water, serves as a sediment trap resulting in severe sand deposition in the navigation channel of the Tam Quan estuary In the long term, additional sand deposition. .. zone, and fine sands are more associated with the wave propagating zone Due to the impact of the jetty, fine sand has accumulated on shoreline at the south side covering a linear distance of 300... reasons for sand deposition in Tam Quan estuary based on the analysis of surface sediment distributions and transport and then propose suitable countermeasures Study area In the central part of Vietnam,