1. Trang chủ
  2. » Khoa Học Tự Nhiên

Response of salinity intrusion to the hydrodynamic conditions and river mouth morphological changes induced by the 2011 tsunami

16 35 0

Đang tải... (xem toàn văn)

Tài liệu hạn chế xem trước, để xem đầy đủ mời bạn chọn Tải xuống

THÔNG TIN TÀI LIỆU

Thông tin cơ bản

Định dạng
Số trang 16
Dung lượng 5,06 MB

Nội dung

In this study, the response of salinity intrusion to the river mouth morphological changes induced by the 2011 Tsunami is investigated. The topographical changes caused by the tsunami are mainly divided into two stages. The first is the direct action of the tsunami, which caused the severe scouring of the coast and the widening of the river. The results have clearly indicated that after tsunami the salt water can intrude much further upstream compare to the condition before the tsunami event.

Journal of Science and Technology in Civil Engineering NUCE 2020 14 (2): 1–16 RESPONSE OF SALINITY INTRUSION TO THE HYDRODYNAMIC CONDITIONS AND RIVER MOUTH MORPHOLOGICAL CHANGES INDUCED BY THE 2011 TSUNAMI Nguyen Xuan Tinha,∗, Jin Wanga , Hitoshi Tanakaa , Kinuko Itob a b Department of Civil Engineering, Tohoku University, 6-6-06 Aoba, Sendai 980-8579, Japan Department of Applied Aquatic Bio-Science, Graduate School of Agriculture, Tohoku University, 468-1 Aramaki Aza Aoba, Aoba-ku, Sendai, Miyagi, 980-8572, Japan Article history: Received 07/03/2020, Revised 29/03/2020, Accepted 31/03/2020 Abstract The 2011 Tohoku Earthquake and tsunami were one of the most devastating natural disasters in history It caused significant ground subsidence and erosion along the Japan coastline The Natori river mouth which is a habitat for both fishes and bivalves, as an important fishing ground, has been damaged by the tsunami because of the change of the process of salt transport in an estuarine system In general, salinity intrusion into the river mouth can be affected by many factors such as river water discharge and tidal level, as well as estuarine morphology In this study, the response of salinity intrusion to the river mouth morphological changes induced by the 2011 Tsunami is investigated The topographical changes caused by the tsunami are mainly divided into two stages The first is the direct action of the tsunami, which caused the severe scouring of the coast and the widening of the river The results have clearly indicated that after tsunami the salt water can intrude much further upstream compare to the condition before the tsunami event Another changes occurred during the restoration process after the tsunami The sediment accumulation in the river channel prevented the saltwater from entering the river channel, which reduced the salt intrusion degree However, the effect of the morphology change caused directly by the tsunami is far greater than the sedimentation of the river Keywords: salinity intrusion; river morphology; tsunami impact; numerical simulation; EFDC model https://doi.org/10.31814/stce.nuce2020-14(2)-01 c 2020 National University of Civil Engineering Introduction Salt intrusion is one of the important problems in estuaries because it affects the quality of surface water and groundwater as well as the aquatic habitat Salinity has been used as an indicator of the water quality for organism distribution [1, 2] The Natori River is an important fishing ground both for bivalves and fishes in central Miyagi prefecture It is important to figure out the salinity distribution in this area, as it will prove invaluable in the maintenance of fishery resources in Miyagi The effects of the Great East Japan Tsunami on fish populations and ecosystem recovery has been studied, which indicates that the distribution and abundance of bivalve can be affected by variations of salinity and depth of the water The brackish area has extended upstream after the tsunami, presumably caused by ∗ Corresponding author E-mail address: nguyen.xuan.tinh.c5@tohoku.ac.jp (Tinh, N X.) Journal of Science and Technology in Civil Engineering NUCE 2018 ISSN 1859-2996 Tinh, N X., et al / Journal of Science and Technology in Civil Engineering 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 ground subsidence in this area [3] The extension of brackish water area may increase the operation estuaries Salt intrusion is generally caused by an imbalance between river and tidal cost for the desalination processes such as using the nanofiltration technique for the drinking water flows butinvariation in seawater treatment the lower Thu Bon River intrusion Basin [4] are also attributable to estuarine geometry Morphological changes during tidalabout variation drastically Based on this background, discussion the salinity distributionaffect in the the Natorilongitudinal River mouth will be conducted This research will reveal the spatial and temporal variations in salinity and the salinity distribution [9, 10] roles of river discharge, tidal period as well as morphology changes in regulating salt transport Because Great Tsunami on 11 March 2011, coastlines Many kinds the of complex processes which such as occurred tidal variation, hydrological flux,many wind stress reflect changes in salinity Numerous efforts have been made to understand the spatial and temporal disand river mouths has been greatly damaged The serious coastal and estuarine tributions of salinity under the external influences of these factors The distribution depends on the morphological changes due to the 2011 tsunami in Tohoku region have been reported estuarine response to river discharge, wind and tidal mixing over time scales from days to weeks and in the study In addition, a detail isstudy of the morphological characteristics of months Thereby is a[11] consensus that salt intrusion inversely correlated to river discharge A high river flow results in amouths decreased salinity The relationship between salt intrusion length and Natori River after the intrusion 2011 tsunami and recovery process have carried outriver by discharge follows a power law with an exponent of n, which varies in different estuaries [5, 6] And [12] Figure shows the aerial photos of the river mouth taken between March 6, the response of salt intrusion to tidal mixing has also been studied extensively, while the relationship 2011 and 2013.differs Comparing (a) and (b), it can be found that more the between saltMarch and tidal4, mixing largely ForFigs a well-mixed or salt wedge estuary, salt intrudes tsunami severely washed away the neap estuary's lagoon area and theobservations, river channel was landward during spring tides than during tides [7] On the other hand, analytical and numerical model results have this indicated thatthe larger upstream flux ora salinity intrusion happens also greatly expanded After event, estuary has salt entered slow recovery phase, during neap tides in partially mixed estuaries The difference has been attributed to the different salt and the washed and broken coastline has gradually become complete again, after transport mechanisms for different estuaries [5, 6, 8] 2013, the shape of the riverprocess mouthcan maintaining a relatively However, In addition, the salt transport be also affected by changesstable in somestate geometric characteristics SuchFigs changes canwith alter 1both hydrodynamics and the rate of mixing in the the coastal ocean, comparing (f) (a),thethere is still a large difference between form of thereby having a profound effect salt transport in estuaries Salt intrusion is generally caused by the estuary and that before theontsunami: a clear sediment accumulation inside the river an imbalance between river and tidal flows but variation in seawater intrusion is also attributable to can be observed 2013 estuarine geometry.inMorphological changes during tidal variation drastically affect the longitudinal salinity distribution [9, 10] (a) 2011-03-06 (b) 2011-03-12 (c) 2011-06-08 (d) 2012-01-18 (e) 2012-09-07 (f) 2013-03-04 91 92 93 94 95 96 97 98 99 100 Figure 1.Aerial photographs of Natori the Natori morphological after the Figure Aerial photographs of the estuaryestuary morphological changes afterchanges the 2011 tsunami 2011 tsunami Because of the Great Tsunami which occurred on 11 March 2011, many coastlines and river (Các has tiêubeen đề nhỏ (a),damaged (b),… để xuống tranh, chèn hình/changes Font chữ mouths greatly The serious coastal andkhông estuarine morphological due to the 2011 tsunami in Tohoku region has been reported in the study by [11] In addition, a detail study Times New Roman thường, khơng đậm—Phần chèn hình phần đen rectify of the morphological characteristics of Natori River mouths after the 2011 tsunami and recovery ảnh đề nghị không thay đổi.) process have carried out by [12] Fig shows the aerial photos of the river mouth taken between March 6, and March 4, 2013 Figs 1(a) and 1(b), it can be found that the tsunami As2011 indicated above, the Comparing general understanding of estuarine dynamics and salt intrusion has advanced greatly in recent decades However, for a specific estuary, such as Natori Estuary in particular, which was under the severe impact of the tsunami, the morphology changed in a short period of time and continued to change in the Tinh, N X., et al / Journal of Science and Technology in Civil Engineering severely washed away the estuary’s lagoon area and the river channel was also greatly expanded After this event, the estuary has entered a slow recovery phase, and the washed and broken coastline has gradually become complete again, after 2013, the shape of the river mouth maintaining a relatively stable state However, comparing Figs 1(f) with 1(a), there is still a large difference between the form of the estuary and that before the tsunami: a clear sediment accumulation inside the river can be observed in 2013 As indicated above, the general understanding of estuarine dynamics and salt intrusion has advanced greatly in recent decades However, for a specific estuary, such as Natori Estuary in particular, which was under the severe impact of the tsunami, the morphology changed in a short period of time and continued to change in the subsequent recovery process, the changes in salt transport have not been quantitatively evaluated so far Therefore, several observation datasets (topographic survey data before and after tsunami, river discharge, water elevation, tidal level) are collected in this study The verified model is used to investigate the impacts of morphology change, river discharge, and tidal level on salt transport in the Natori River Estuary The purpose of this study is to quantitatively evaluate the changes in salinity distribution induced by factors with different time scales, from weeks (springneap tide) to months (seasonal river discharge change) and years (morphology change), then identify the extent to which each factor affects changes in salinity The results obtained provide significant implications for the sustainable development of the estuarine system and the local fishery revival Materials and methods 2.1 Study area The Natori River is located in central Miyagi prefecture, in the Tohoku region of northern Japan, which is listed as a first-class river according to the River Act of Japan (Ministry of Land, Infrastructure, Transport and Tourism (2013)) The Natori River is approximately 55 km in length, and has 13 branches The basin area is about 939 km2 , yearly averaged discharge is 16.32 m3 /s The Natori River Estuary is located on Japan’s east coast, and faces the Pacific Ocean (Fig 2) The river divided into two branches about 5.5of km upstream fromin the mouth, one the Hirose River, which Journal Science and Technology Civil river Engineering NUCE 2018of which ISSNis1859-2996 Hirosebashi discharge St SENDAI Fukurobara water level St JAPAN Natoribashi discharge St Yuriage water level St (km) 133 Figure2.2.Location Location of Figure of the thestudy studyarea area 134 135 2.2 Data collection 136 137 138 139 140 In this study, to achieve the above objectives, the required data sets are the bathymetry data in different years before and after the tsunami, river discharge and tidal elevation were specified as boundaries, water level and salinity were used for model calibration and verification Table is the list of all data available from 20092016 Tinh, N X., et al / Journal of Science and Technology in Civil Engineering passes through the city of Sendai In the downstream close to the coast, there is the Idoura Lagoon on the north coast and Hiroura Lagoon on the south coast The Great East Japan Earthquake and Tsunami in March 2011 were one of the most devastating natural disasters in history, affecting the society, economy, coastlines, infrastructure, and housing In addition to affecting human life, the subsequent tsunami also struck organisms living in the water Miyagi Prefecture is the second largest fishery landing region in Japan and as a result of the tsunami this fishery was heavily affected: many ships were lost; ports and jetties were destroyed [13] The Natori River is an important fishing ground both for bivalves and fishes, various fish species live in brackish water areas, which are very important for the maintenance of fishery resources [3] The tsunami resulted in significant ground subsidence and deposition of rubble and mud in the Natori River 2.2 Data collection In this study, to achieve the above objectives, the required data sets are the bathymetry data in different years before and after the tsunami, river discharge and tidal elevation were specified as boundaries, water level and salinity were used for model calibration and verification Table is the list of all data available from 2009-2016 Table Summary of the data collection from 2009-2016 (Black dots indicate the data availability) [14] Morphology Water level Tidal River discharge • • • • • • • • • • • • • • • • • • • • • • 2009 2010 2011 2012 2013 2014 2015 2016 • • • • Salinity • • • a Bathymetry data The topographic map of 2009 was used as the bottom elevation before the tsunami From 2011 to 2015, the bottom elevation of shallow coastal terrain was measured every one kilometer along the coast of the Sendai Bay with the survey line which is perpendicular to the coastline, which was carried out by the Geospatial Information Authority of Japan On the other hand, the Tohoku Regional Bureau, Ministry of Land, Infrastructure and Transport (MLIT) provided the bottom topography data of sections, with the survey line which is perpendicular to the channel, within a distance of 0.6 km from the ocean side to the Natori River mouth as shown in Fig By combining these two data sets, the detailed topograpthic maps of the Natori estuary can be determined for each year by an interpolation process b Hydrodynamic data There are two river discharge measurement stations located in the upstream of the study area which are Hirosebashi station located on the Hirose river branch and Natoribashi station on the Natori river These river discharge stations are located far enough to avoid the impacts by the tidal motion In topography data of sections, with the survey line which is perpendicular to the channel, within a distance of 0.6km from the ocean side to the Natori River mouth as shown in Fig By combining these two data sets, the detailed topograpthic maps of the Natori estuary beal.determined for each year by anininterpolation process Tinh, N.can X., et / Journal of Science and Technology Civil Engineering Elevation (m) 152 153 154 155 Before tsunami 2011 (After tsunami) 2012 2013 2014 Mean sea level -2 -4 -6 100 200 300 Section D 400 500 600 Elevation(m) Distance (m) -2 -4 -6 Section B Elevation(m) -2 -4 -6 156 100 200 300 400 Distance (m) 500 600 Section A 100 200 300 400 Distance (m) 500 600 Natori river mouth transection measurement data before and the 2011 tsunami 157 Figure Figure Natori river mouth transection measurement dataafter before and after the[MLIT] 2011 158 tsunami [MLIT] addition, there are two water level stations where Fukurobara station is located upstream and Yuriage station is located downstream near the estuary respectively Annual, monthly and hourly river dis6 charge and water level data for hydrodymanic stations are provided by the Japan Meteorological Agency (JMA) website [14] The tidal levels used in this study are obtained from hourly measured data at Sendai Port station, provided by the JMA [14] The distribution of tidal phases in the Natori River estuary is mixed tide and the tidal range is from about 0.8 m to 1.6 m The tidal amplitudes decrease gradually when the tide propagates upstream c Salinity data In this study, measured salinity data for the three years from 2013 to 2015 were used This salinity data was provided by the College of Agriculture, Tohoku University As shown in Fig 4, there are three salinity measurement points, St.A, St.B., and St.C respectively St.A as the basic setting point, located under the Yuriage Ohashi Bridge, with coordinates of 38◦ 10.949N, 140◦ 8.850E St.B is located downstream which is very close to the estuary, St.C is located upstream of the Yuriage Ohashi Bridge, in the deep waters near the right bank All of the measurement point is set 10-20 cm from the bottom of the river bed elevation 177 178 179 180 181 St.B., and St.C respectively St.A as the basic setting point, located under the Yuriage Ohashi Bridge, with coordinates of 38°10.949N, 140°8.850E St.B is located downstream which is very close to the estuary, St.C is located upstream of the Yuriage Ohashi Bridge, in the deep waters near the right bank All of the measurement point is X.,bottom et al / Journal Science Technology in Civil Engineering set 10-20 cmTinh, fromN.the of the of river bed and elevation Logger St.C Yuriage Ohashi Br Logger St.B Logger St.A Sendai Bay 500m 182 183 Journal of Science and Technology in Civil Engineering NUCE 2018 ISSN 1859-2996 Figure The location of salinity measurement stations Figure The location of salinity measurement stations 184 181 The salinity measurement is divided into two periods From 2014 to 2015, a periods.water 182 salinity sensor named the YSI 6920V2 was used The sensor named The salinity measurement is divided into twomulti-item Fromquality 2014meter to 2015, a salinity 183 measurable items include salinity, water temperature, turbidity, water depth, pH, the YSI 6920V2 multi-item water quality meter was used The measurable itemsetc.include salinity, 184 The salt measurement range is 0-70ppt, with the resolution 0.01ppt On these two water temperature, turbidity, water depth, pH, etc The salt measurement range is 0-70 ppt, with the 185 years, the measuring interval is 10 minutes, and the salinity changes at measurement resolution 0.01 ppt On these two years, the measuring interval is 10 minutes, and the salinity changes 186 points St.A and St.B were mainly measured, besides, in a few months, the salinity data at measurement points St.A and St.B were mainly measured, besides, in a few months, the salinity 187 at St.C was also measured From 2016, the salinity measuring instrument was changed data at St.C was also measured From 2016, the instrument was changed to the 188 to the small memory water temperature andsalinity salt metermeasuring INFINITY-CT, the measurable small memory waterinclude temperature INFINITY-CT, the sensor measurable items 189 items salinity and and salt watermeter temperature This salinity employs a 7-include salinity and water temperature This salinity sensor employs a 7-electrode in-tube method for the electrical 190 electrode in-tube method for the electrical conductivity sensor with a high-precision conductivity sensor with a high-precision The observation interval is minute, and 191 The observation interval is minute, and the salinity is converted by measuring the the salinity is converted192by measuring themeasurement water body,range the measurement is 0.5-70 mS/cm, conductivitythe of conductivity the water body,ofthe is 0.5-70mS/cm,range and the and the resolution is 0.001 mS/cm, the precision is ±0.05 mS/cm In 2016, only the salinity data of 193 resolution is 0.001mS/cm, the precision is ±0.05mS/cm In 2016, only the salinity data measurement St.A was measured An example of theoftime variation salinity data at three 194 point of measurement point St.A was measured An example the time variationof of salinity station is195 shown in Fig data at three station is shown in Fig Salinity (ppt) St.A Salinity (ppt) St.B Salinity (ppt) St.C Date 196 197 198 Figure variationofofthethe measured salinity the St.A, St.B and St.C Figure 5 Time Time variation measured salinity data data at theatSt.A, St.B and St.C from from January to March in 2015 January to March in 2015 199 2.3 Numerical model and model setup 200 a) Numerical model 201 In this study, a three-dimensional numerical EFDC+ (Environmental Fluid Dynamics Code Plus) model is used [15] This is an open-source code model that can be downloaded from the website at https://github.com/dsi-llc/EFDCPlus In recent years, this model has been widely used in the study of estuarine hydrological environment and salt distribution Through the model results after verification, it can 202 203 204 205 Tinh, N X., et al / Journal of Science and Technology in Civil Engineering 2.3 Numerical model and model setup a Numerical model In this study, a three-dimensional numerical EFDC+ (Environmental Fluid Dynamics Code Plus) model is used [15] This is an open-source code model that can be downloaded from the website at https://github.com/dsi-llc/EFDCPlus In recent years, this model has been widely used in the study of estuarine hydrological environment and salt distribution Through the model results after verification, it can provide more accurate and clear temporal and spatial changes of salinity in different estuaries The study by [16] predicted the hydro-environmental impacts of a renewable energy structure, including sluice gates and turbines, across the Severn Estuary by refinements to the EFDC model In particular, a comparison between salinity concentration distributions predicted by the 2D and 3D models indicated that near the barrage site, the salinity levels predicted slightly different both on the upstream and downstream Hence, it is preferable to use a 3D model for more detailed and accurate hydrodynamic and solute concentration distributions Gong and Shen [17] studied salt intrusion in the Modaomen Estuary, one of the estuaries in the PRD area, China The EFDC model was calibrated and verified for water elevation, water current, and salinity Their result indicated that the estuary gains salt during neap tides and loss salt during spring tides and a river discharge pulse suppresses the salt intrusion greatly Yoon and Woo [18] applied EFDC model in tidally-dominated Han River Estuary, South Korea to understand the along-channel salinity distribution and its response to river discharge Although in a tidally-dominated estuary, freshwater discharge is still the primary environmental factor controlling the salinity The model solves the three dimensional continuity and free surface equations of motion [19] The Mellor and Yamada level 2.5 turbulence closure scheme is implemented in the model [20] The model also solves the three dimensional continuity and free surface equations of motion The model uses stretched vertical coordinates and curvilinear, orthogonal horizontal coordinates It simulates density and topographically induced circulation as well as tidal and wind-driven flows, and spatial and temporal distributions of salinity, temperature, and conservative/non-conservative tracers The model has a flexible grid network structure, which is capable of linking multiple tributaries to the main channel through grid linkage between upstream and downstream grid cells, including dam structures The model has been successfully applied to a wide range of environmental studies [16–18, 21] b Numerical setup Fig shows the model grid, bottom elevation of the Natori River Estuary, and the location of each measurement stations The EFDC model domain covers the Natori River Estuary and upstream to the Hirose River and the Natori River, where two hydrological stations, Hirosebashi and Natoribashi, are located To ensure that the study area was fully covered by the model, the boundary with the open sea was extended approximately km to the offshore A curvilinear and orthogonal grid was used over the entire domain, and this refined grid was utilized for the Natori River Estuary The horizontal spatial resolution ranges from about 300 m at offshore to 10 m in the area near the river channels Several sensitivity tests were conducted for the vertical resolution using 5, 10, 15, and 20 sigma layers in the vertical It was found that using 15 layers improved model results considerably compared to and 10 layers, whereas 20 layers did not improve results further Thus, the use of 15 sigma layers was adopted in the vertical direction Sufficient grid resolution was provided to adequately schematize the bottom elevation of the Natori River Estuary At the two upstream boundaries of the two hydrological stations, Hirosebashi and Natoribashi, Hourly river discharges were specified as the inflowing boundaries with an inflowing salinity of 244 245 246 247 248 vertical resolution using 5, 10, 15, and 20 sigma layers in the vertical It was found that using 15 layers improved model results considerably compared to and 10 layers, whereas 20 layers did not improve results further Thus, the use of 15 sigma layers was adopted in the vertical direction Sufficient grid resolution was provided to Tinh, schematize N X., et al the / Journal of elevation Science and in Civil Engineering adequately bottom of Technology the Natori River Estuary Hirosebashi Natoribashi Fukurobara St.A Yuriagedaini Bottom elevation (m) -24 12 249 Figure Figure Model6.grid showing bottom bottom elevation and theand locations of the of upstream boundaries 250 Model grid showing elevation the locations the upstream boundaries 251 252 on statistical At theresult two upstream boundaries of The the two hydrological stations,were Hirosebashi zero based of observation data upstream boundaries set with sufficient 253 and Natoribashi, Hourly river discharges were specified as the inflowing boundaries distance from the Natori River Estuary to ensure that any effects from morphology changes were 254 The with an inflowing salinity of zerofor based on statistical result of observation data The negligible water levels were specified offshore open boundary conditions, allowing the tidal 255 upstream boundaries were set with sufficient distance from the Natori River Estuary to flow to freely propagate across the model domain In this study, one coastal open boundary was set 256boundary, ensure that any was effects from by morphology changes obtained were negligible Thehourly water levels at the east which forced water elevation from the observation data 257 were specified for offshore open boundary conditions, allowing the tidal flow to freely in Sendai Bay station References to the average salinity of the world’s oceans and the measured 258 propagate across the model domain In this study, one coastal open boundary was set data of salinity in this study, the incoming salinities at the offshore open boundary were specified as 259 at the east boundary, which was forced by water elevation obtained from the hourly 35 ppt With regard to the initial hydrodynamic conditions, the water elevation was set as zero over the 260 observation data in Sendai Bay station References to the average salinity of the domain To obtain the initial conditions for salinity, the model was run iteratively for approximately 261 world's oceans and the measured data of salinity in this study, the incoming salinities 30 days using the forced boundary conditions The resulting salinity distribution at the end of the 262 at the offshore open boundary were specified as 35ppt With regard to the initial simulation was used as the initial salinity condition in all cases 263 hydrodynamic conditions, the water elevation was set as zero over the domain To Model calibration and validation 10 In this study, the bathymetry data input to the model adjusted the topography for each year after the tsunami, considering the possible impact on the accuracy of the estuary salt distribution results simulated by the model, and the feasibility of verifying this method, the model calibration and verification were done in 2014-2016, all of the three years that have available salinity data The simulation period for the model calibration was from December to 31 in 2014, January to 31 in 2015, and April to 30 in 2016 respectively; and the model verification was from August to 31 in 2014 The available boundary conditions during the period were implemented into the model 3.1 Calibration of water level The modeled water elevations were compared with the observations data The root–mean–square error (RMSE) and Nash–Sutcliffe Efficiency coefficient (NSE) were used to assess the model accu8 ISSN ISSN 1859-2996 1859-2996 Journal Journal of Science of Science and and Technology Technology in Civil in Civil Engineering Engineering NUCE NUCE 20182018 2015 2015 Yuriagedaini Yuriagedaini 0.081 0.081 0.945 0.945 Tinh, N X., et al / Journal of Science and Technology in Civil Engineering Fukurobara Fukurobara 0.165 0.165 0.527 0.527 Yuriagedaini Yuriagedaini 0.114 0.114 0.907 0.907 racy of the model These criteria are defined as following: 2016 2016 Σ(M − D)2 RMSE = (1) n Average Average 0.117 0.117 0.792 0.792 Σ(M − D)2 NSE = − (2) ¯ agreed Σ(Dlevels − D) As As shown shown in Fig in Fig 7, the 7, the modeled modeled water water levels agreed wellwell withwith the the observations observations 291291 292292where at the atDthe two two hydrological hydrological stations stations inthe the inmean the Natori Natori River River Estuary, Estuary, and and the model evaluation evaluation is the observational data, D¯ is of the observational data, andthe M model is the corresponding 293293modeled index index values values of water of water elevations elevations are are shown shown in Table in Table In each In each year, year, the the results results of of data As shown in Fig 7, the modeled water levels agreed well with the observations at the two hydro294294 downstream downstream station station (Yuriagedaini) (Yuriagedaini) are are generally generally better better thanthan the the upstream upstream station station stations inThe theThe Natori River Estuary, and thethe model evaluation index values ofdata water elevations 295295logical (Fukurobara) (Fukurobara) averaged averaged RMSE RMSE between between the modeled modeled andand observed observed data was was 0.117 0.117 are shown in Table In each year, the results of downstream station (Yuriagedaini) are generally bet296296 m m TheThe NSE NSE values values for for the the results results at different at different stations stations varied varied from from 0.527 0.527 to 0.945, to 0.945, ter than the upstream station (Fukurobara) The averaged RMSE between the modeled and observed 297297data indicating indicating thatm that theThe the modeled modeled water water levels levels achieved achieved veryvery good good performance performance was 0.117 NSE values for the results at different stations varied from 0.527 to 0.945, indicating that the modeled water levels achieved very good performance 298298 Measured Measured datadata  (m)  (m)  (m)  (m)  (m)  (m)  (m)  (m)  (m)  (m)  (m)  (m) Model Model result result DateDate DateDate (a) –variation (a) Time – Time variation variation comparison of atof (a) Time comparison ofcomparison water level Fukurobara station in Fukurobara 2014, 2015, 2016 water water level level at Fukurobara at station station in in 299299 300300 (b)(b)Time variation comparison of wateroflevel –(b) Time – Time variation variation comparison comparison ofat Yuriage station in 2014, 2015, 2016 water water levellevel at Yuriage at Yuriage station station in in 2014, 2014, 2015, 2015, 20162016 2014, 2014, 2015, 2015, 20162016 Figure Water level calibration results Figure Figure Water Water level level calibration calibration results results 12 12 Tinh, N X., et al / Journal of Science and Technology in Civil Engineering Table The model evaluation index values for calibration of water level in 2014, 2015 and 2016 Year Station RMSE (m) NSE 2014 Fukurobara Yuriagedaini 0.133 0.122 0.726 0.849 2015 Fukurobara Yuriagedaini 0.086 0.081 0.798 0.945 2016 Fukurobara Yuriagedaini 0.165 0.114 0.527 0.907 0.117 0.792 Average 3.2 Calibration of salinity Fig shows comparisons between the modeled and observed salinities in the estuary, and the model evaluation index values for calibration of salinity shows in Table The model results were particularly accurate when reproducing the salinity of St.A and St.B in 2014 and 2015, with the RMSE less than 3.9, and NSE over 0.64 Although the trough of salinity variation did not capture well in the St.C, but the evaluation index values in most stations are showing a good performance, of Science and Technology Civil Engineering 1859-2996 Although of Science and CivilinEngineering NUCENUCE 2018 ISSN 1859-2996 suggesting Journal that Journal the model is Technology capable ofinaccurately simulating the 2018 process ofISSN salt transport Salinity (ppt) St.A St.A Salinity (ppt) Salinity (ppt) Salinity (ppt) Measured ModelModel result result Measured data data St.B St.B 317 Date Date (a) – Time variation comparison of (a) – Time variation comparison of in (a) Time variation comparison of salinity salinity in 2014, 2015, 2016 salinity in 2014, 2015, 2016 2014, 2015, 2016 317 Salinity (ppt) Salinity (ppt) St.C St.C Salinity (ppt) Salinity (ppt) Salinity (ppt) Salinity (ppt) Salinity (ppt) Salinity (ppt) St.A St.A St.B St.B St.A St.A Date Date (b) – Time comparison of (b) – Time variation comparison of salinity (b) Time variation variation comparison of the thein salinity in 2014, 2015, 2016 the salinity in 2014, 2015, 2016 2014, 2015, 2016 Figure Salinity calibration result Figure calibration result Figure Salinity Water level calibration results Results and discussion 319 319 Results and discussion 318 318 4.1 Numerical simulation scenarios 320 320 4.1 Numerical simulation scenarios 10 In order to evaluate the different the three factors discharge, 321 321 In order to evaluate the different extentextent of theofthree factors (river(river discharge, tide, tide, and morphology changes) impact the salinity transport mechanism the Natori 322 322 and morphology changes) impact on theonsalinity transport mechanism of theofNatori Tinh, N X., et al / Journal of Science and Technology in Civil Engineering the discrepancies between the modeled and observed salinities were significantly greater than those for simulations of the water level, the salinities modeled in this study are generally considered to be acceptable Table The model evaluation index values for calibration of salinity in 2014, 2015 and 2016 Station RMSE (ppt) NSE 2014 A B 3.628 3.900 0.836 0.748 2015 A B C 3.585 3.701 2.453 0.815 0.641 0.805 2016 A 5.129 0.729 3.733 0.762 Average Results and discussion 4.1 Numerical simulation scenarios In order to evaluate the different extent of the three factors (river discharge, tide, and morphology changes) impact on the salinity transport mechanism of the Natori River Estuary, after obtaining the ideal calibration result, at the stage of analysis, different scenarios were designed and simulated to quantify the salinity distribution in estuary under different conditions In order to assess the salinity intrusion into the estuary under different flow conditions throughout the year, three different inflowing boundary conditions such as high discharge, normal discharge and low discharge were set at the two upstream boundaries at the Hirosebashi Station, and the Natoribashi Station respectively High river discharge is defined as 95 days of river discharge in a year not less than this value; normal river discharge is 185 days of river discharge in a year not less than this value; low discharge is 275 days of river discharge in a year not less than this value The specific values are calculated based on the information provided by the Japan Meteorological Agency website [13] from year of 1969 to 2016 and Journal of Science andhigh Technology in Civil Engineering ISSN 1859-2996 shown in Table Specifically, in Hirosebashi station, the discharge is: 11.73 NUCE m3 /s;2018 the normal Table The determine the high-, normal-, and low-mean river discharges based on the data collected between 1969 and 2016 Hirosebashi (m3 /s) High discharge Normal discharge Low discharge 11.73 6.26 3.62 Natoribashi (m3 /s) 15.17 7.81 355 4.67 356 357 Figure Description of the tides on the example of one day Figure Description of the tides on the example of one day 358 4.2 Effect of river discharge and tidal level on salinity instrusion length 359 360 361 In order to quantify salt transport and to analyze the controlling mechanisms, 11 the distributions in salinity along the longitudinal section from the river mouth at the Section A (Fig 3) to the river upstream Figure 10 is the numerical simulation results of the longitudinal distribution of salinity corresponding the actual bathymetric conditions in the years of 2009 and 2014 These two simulation cases represent to the 362 363 Tinh, N X., et al / Journal of Science and Technology in Civil Engineering discharge is: 6.26 m3 /s; the low discharge is: 3.62 m3 /s In Natoribashi station, the high discharge is: 15.17 m3 /s; the normal discharge is: 7.81 m3 /s; the low discharge is: 4.67 m3 /s In total, there simulation scenarios were set up which consisted of three typical river discharges over three different bathymetries in 2009, 2013, and 2014 The models were simulated over one month tidal cycle to cover the spring tide and neap tide effects The analysis of simulation results will focus on the salinity distribution during the high, normal, and low river discharge, as well as during the different tidal asand shown in Fig Journal of stages Science Technology inin Civil ISSN Journal of Science and Technology CivilEngineering EngineeringNUCE NUCE2018 2018 ISSN1859-2996 1859-2996 4.2 Effect of river discharge and tidal level on salinity instrusion length 356 and after the event The were under In order before tobefore quantify transport andtsunami to analyze the controlling mechanisms, the distributions 356 situation situation andsalt after the2011 2011 tsunami event Theresults results werecompared compared under in salinity along the longitudinal section from the river mouth at the Section A (Fig 3) to thetoto river 357 the high, normal and low river discharge during a whole spring-neap tidal cycle 357 the high, normal and low river discharge during a whole spring-neap tidal cycle Fig 10 is the numerical simulation results of the in longitudinal distribution of salinity 358 detect inin the vertical ofofsalinity River As 358upstream detectchanges changes the verticalstratification stratification salinity inthe theNatori Natori RiverEstuary Estuary Asa acorresponding to the actual bathymetric conditions in the years of 2009 and 2014 These two simulation 359 359 result, result,thethelongitudinal longitudinaland andvertical verticaldistributions distributionsofofsalinity salinitybefore beforeand andafter afterthe the2011 2011 cases represent to the situation before and after the 2011 tsunami event The results were compared un360 arearedistinctly intrusion after during 33stages 360derevent event distinctly different Moresalinity salinity intrusion afterthe thetsunami tsunami during stages the high, normal anddifferent low river More discharge during a whole spring-neap tidal cycle to detect changes 361 it itis ismainly due river mouth morphological 361in of ofriver riverflow, flow, mainly duetotothe river mouth morphological changes Underhigh highand the vertical stratification of salinity inthe the Natori River Estuary As a changes result, the Under longitudinal of salinity before and after salt the 2011 event was are distinctly different More salinity 362 river discharge nonosignificant intrusion observed inin2009 While 362vertical riverdistributions dischargeconditions, conditions, significant salt intrusion was observed 2009 While intrusion after the tsunami during stages of river flow, it is mainly due to the river mouth morpho363 thetheriver 363 asas riverdischarge dischargedecreases, decreases,the thesalt saltintrusion intrusionininthe theestuary estuarybecome becomevery veryobvious obvious logical changes Under high river discharge conditions, no significant salt intrusion was observed in 364 364 Under Underthetheconditions conditionsofofnormal normaland andlow lowdischarge, discharge,near nearthe theriver rivermouth, mouth,salinity salinityininthe the 2009 While as the river discharge decreases, the salt intrusion in the estuary become very obvious 365 bottom the range ofofmore than ininthe 365Under bottom waterlayer layer almostalways always changeswithin within the range more than 20 ppt the the water conditions ofalmost normal and lowchanges discharge, near the river mouth, salinity in20 theppt bottom water 366 366 year yearofof2014 2014and andthe thesalinity salinityintrusion intrusionlength lengthhas hasalso alsogreatly greatlyincreased increased High flow High flow Salinity (ppt) Salinity (ppt) Elevation (m) Elevation (m) Elevation (m) Elevation (m) High flow High flow Normal flow Normal flow Salinity Salinity(ppt) (ppt) Low flow Low flow Low flow Low flow Salinity (ppt) Salinity (ppt) Distance from river mouth (m) Distance from river mouth (m) 368 368 369 369 Elevation (m) Elevation (m) Salinity (ppt) Salinity (ppt) – Longitudinal distribution salinitythe (a)(a) – Longitudinal distribution of of salinity (a) Longitudinal distribution of salinity during during high-, nomallow-flow 2009 during thethe high-, nomalandand low-flow in in 2009 high-, nomaland low-flow in 2009 Elevation (m) Elevation (m) Elevation (m) Elevation (m) Elevation (m) Elevation (m) Normal flow Normal flow 367 367 Salinity Salinity(ppt) (ppt) Salinity(ppt) (ppt) Salinity Distance from river mouth(m) (m) Distance from river mouth (b) – Longitudinal distribution salinity – Longitudinal distribution ofofsalinity (b) (b) Longitudinal distribution of salinity during the during high-, nomaland low-flow in2014 2014 during thethe high-, nomallow-flow high-, nomalandand low-flow inin2014 Figure 10 Longitudinal distribution salinity during thehigh, high, normal andlow low river Figure 10 Longitudinal distribution ofofsalinity during river Figure 10 Longitudinal distribution of salinity during the high, the normal andnormal low riverand flow (a) in 2009 (before the tsunami event) and (b) in 2014 (after the tsunami event) flow (a) in 2009 (before the tsunami event) and (b) in 2014 (after the tsunami event) flow (a) in 2009 (before the tsunami event) and (b) in 2014 (after the tsunami event) 370 addition,short-term short-termchanges changesininsalinity salinityare arealso alsovery verysensitive sensitivetotothe thetide tide 12 370 InInaddition, 371 periods periods.AsAsshown shownininFig Fig.11, 11,salt saltisisintruded intrudedinto intothe theestuary estuaryduring duringthe theflood-tide flood-tide 371 372 periods; periods;thethesalinity salinitythus thusincreases, increases,and andthe themaximum maximumsalt saltintrusion intrusionoccurs occursatatflood flood 372 373 slack slack.However, However,salt saltis isexpelled expelledfrom fromthe theestuary estuaryduring duringebb-tide ebb-tideperiods; periods;the thesalinity salinity 373 Tinh, N X., et al / Journal of Science and Technology in Civil Engineering (m) Elevation (m) Elevation Salinity Salinity(ppt) (ppt) Salinity Salinity(ppt) (ppt) Ebb Ebbslack slack Salinity Salinity(ppt) (ppt) Ebb Ebbpeak peak Distance Distancefrom fromriver rivermouth mouth(m) (m) 379 379 (m) Elevation (m) Elevation Flood Floodpeak peak Salinity Salinity(ppt) (ppt) Flood Floodslack slack Flood Floodpeak peak (m) Elevation (m) Elevation Salinity Salinity(ppt) (ppt) Flood Floodslack slack Ebb Ebbslack slack (m) Elevation (m) Elevation Elevation (m) Elevation (m) Elevation (m) Elevation (m) Elevation (m) Elevation (m) Elevation (m) Elevation (m) layer almost always changes within the range of more than 20 ppt in the year of 2014 and the salinity intrusion length has also greatly increased In addition, short-term changes in salinity are also very sensitive to the tide periods As shown in Fig 11, salt is intruded into the estuary during the flood-tide periods; the salinity thus increases, and the maximum salt intrusion occurs at flood slack However, salt is expelled from the estuary during Journal Science and Civil Engineering NUCE ISSN Journalofof Science andTechnology Technologyinin Civil Engineering NUCE 2018 ISSN1859-2996 1859-2996 ebb-tide periods; the salinity decreases, and the minimum salt2018 intrusion occurs at ebb slack During the same tidal period, due to the effects of high tide and low tide, the difference between the maximum salt intrusion length in the estuary varies from 300 to 2000 meters, with the increased tidal range in 377 377 increased increasedtidal tidalrange rangeininthe thespring springtide, tide,the thesalt saltintrusion intrusionlength lengthatatits itshigh hightide tidelevel levelisis the spring tide, the salt intrusion length at its high tide level is always longer than that of neap tide 378 always longer than that of neap tide 378 always longer than that of neap tide Ebb Ebbpeak peak Salinity Salinity(ppt) (ppt) Salinity Salinity(ppt) (ppt) Salinity Salinity(ppt) (ppt) Distance Distancefrom fromriver rivermouth mouth(m) (m) (a)(a) Longitudinal distribution of salinity due to (a) Longitudinal distribution salinity ––Longitudinal distribution ofofsalinity effects of tidal level in 2009 duethe theeffects effects tidal level 2009 due totothe ofoftidal level inin2009 (b)(b) Longitudinal distribution of salinity due to (b) Longitudinal distribution salinity ––Longitudinal distribution ofofsalinity the effects of of tidal level in 2014 dueto tothe the effects oftidal tidal level 2014 due effects level inin2014 11.11 Longitudinal distribution ofof salinity during different stages ofofof tidal cycle (a) ininin 2009 380 Figure Figure 11 Longitudinal distribution ofsalinity salinity during different stages tidal cycle (a) 380 Figure Longitudinal distribution during different stages tidal cycle (a) (before the tsunami event) and (b) in 2014 (after the tsunami event) 381 2009(before (beforethe thetsunami tsunamievent) event)and and(b) (b)inin2014 2014(after (afterthe thetsunami tsunamievent) event) 381 2009 382 4.3 4.3.Effect Effectofofriver rivermouth mouthmorphological morphologicalchange changeon onsalinity salinity 382 4.3 Effect of river mouth morphological change on salinity 383 Figure12 12shows showsaacomparison comparisonofofthe themaximum maximumsalinity salinityintrusion intrusionlength lengthduring during 383 Figure Fig 12 shows a comparison of the maximum salinity intrusion length during the 384 the thehigh hightide tideand andlow lowtide tideperiod periodfor forthree threedifferent differentyears yearsofof2009, 2009,2013 2013and and2014 2014.high The tide and 384 The low period for three suggests different years oftopographic 2009, 2013subsidence and 2014 caused The previous suggests that 385tideprevious previous analysis suggeststhat thatthe the topographic subsidence caused bythe theanalysis tsunamiand and 385 analysis by tsunami the topographic subsidence caused by the tsunami and the severe erosion of the beach near the estuary 386 the thesevere severeerosion erosionofofthe thebeach beachnear nearthe theestuary estuaryresulted resultedininmore moreseawater seawaterpouring pouringinto into 386 resulted in more seawater pouring into the river and the salinity concentration increased significantly 387 the the river river and and the the salinity salinity concentration concentration increased increased significantly significantly Due Due toto the the limited limited 387 Due to the limited range of traceability of seawater under high river discharge conditions, this change 388 range rangeofoftraceability traceabilityofofseawater seawaterunder underhigh highriver riverdischarge dischargeconditions, conditions,this thischange changeinin 388 in salinity distribution caused by topographic differences is more pronounced at low and normal river 389 salinity salinity distribution caused by topographic differences is more pronounced at lowdifference and 389 distribution caused by topographic differences is more pronounced at low and discharge Comparing the situation before and after the tsunami, there is a significant in 390 normal normalriver riverdischarge discharge.Comparing Comparingthe thesituation situationbefore beforeand andafter afterthe thetsunami, tsunami,there thereisis 390 391 aa significant significant difference difference inin the the maximum maximum13 salt intrusion intrusion length length before before and and after after the the 391 salt 392 tsunami tsunamievent event.Here, Here,the themaximum maximumintrusion intrusionlength lengthisisdefined definedasasaadistance distancefrom fromthe the 392 17 17 404 in a highly stratified state, the salinity isohaline is nearly horizontal However, because the topographic changes increase the mixing of freshwater and saltwater 405 405 the topographic changes increase the mixing effect effect of freshwater and saltwater at the at the estuary the stronger tidal mixing generally weakened the stratification of 406 406 estuary area, area, the stronger tidal mixing effect effect generally weakened the stratification of 407 the water column and destroyed the salt wedge in the corresponding cases after the 407 the water column and destroyed the salt wedge in the corresponding cases after the 408 tsunami 408 tsunami Tinh, N X., et al / Journal of Science and Technology in Civil Engineering 18 12 24 18 12 18 12 30 Salinity (ppt) Salinity (ppt) 24 30 24 24 12 (c) Low(c) discharge Low discharge 24 18 12 30 1000 2000 18 12 2000 3000 3000 4000 4000 5000 5000 (b) Normal discharge (b) Normal discharge 18 12 1000 1000 2000 2000 3000 3000 4000 4000 5000 5000 (c) Low(c) discharge Low discharge 30 24 24 18 12 2000 2000 3000 3000 4000 4000 5000 5000 01000 1000 Distance from river mouth Distance from river (m) mouth (m) 1000 2000 1000 3000 2000 4000 3000 5000 4000 5000 DistanceDistance from river mouth from river(m) mouth (m) (a) During high tide 409 409 1000 30 18 2009 2013 2014 12 01000 1000 2000 2000 3000 3000 4000 4000 5000 5000 0 30 (b) Normal discharge (b) Normal discharge 2009 2013 2014 18 Salinity (ppt) 30 Salinity (ppt) Salinity (ppt) 24 24 01000 1000 2000 2000 3000 3000 4000 4000 5000 5000 0 30 Salinity (ppt) Salinity (ppt) 12 Salinity (ppt) 12 18 Salinity (ppt) 18 High discharge (a) High(a) discharge 30 30 2009 2009 24 2013 2013 2014 2014 18 12 24 Salinity (ppt) 24 High discharge (a) High(a)discharge 30 Salinity (ppt) Salinity (ppt) 30 (b) During low tide (a) During high tide (a) During high tide (b) During low tide (b) During low tide Figure 12 Maximum salinity intrusion length before and after the 2011 tsunami 18 18 the maximum salt intrusion length before and after the tsunami event Here, the maximum intrusion length is defined as a distance from the 0.0 km of the river to the ppt contour in the upstream Table summarizes all maximum salinity intrusion length during the different conditions of river flow and tidal periods The salinity intrusion length and concentration before the tsunami event in 2009 are much shorter and smaller compare to the situation after tsunami in 2013 and 2014 By comparing the results of 2013 and 2014, it can be found that, due to the obvious sediment deposition inside the river channel in 2013, which prevented seawater invasion to a certain extent, the salt intrusion in the estuary in that year was weaker than in 2014, but the increase in salt transport caused by tsunami is significantly stronger than the weakening effect from sand deposition In addition, by comparing the longitudinal distribution of salinity before and after the tsunami, the vertical stratification has Table The Maximum salinity intrusion length – Unit is meter High discharge Year 2009 2013 2014 Normal discharge Low discharge High tide Low tide High tide Low tide High tide Low tide 120 2410 2490 1480 1680 630 3360 3480 510 2360 2480 1700 3850 4060 1680 3010 3060 14 Tinh, N X., et al / Journal of Science and Technology in Civil Engineering also changed significantly In 2009, the estuary was mainly in a highly stratified state, the salinity isohaline is nearly horizontal However, because the topographic changes increase the mixing effect of freshwater and saltwater at the estuary area, the stronger tidal mixing effect generally weakened the stratification of the water column and destroyed the salt wedge in the corresponding cases after the tsunami Conclusions In this study, the EFDC model was used to quantitatively evaluate the impacts from river discharge, tidal and the morphology change caused by tsunami on salt transport in the Natori River Estuary The model calibration and validation using observed data collected from 2014 to 2016 indicate that the model successfully simulated the dynamic processes and salinity distribution in the estuary The simulation results of salinity distribution in the river mouth were compared under different conditions The modeled results indicate that the river discharge greatly affects the change of salinity, and it directly determines whether the salt intrusion occurs in the estuary At the same time, the salt distribution also responds to the cyclical changes in the tide level during a short term period Due to the impact of the 2011 tsunami, the increase of river month width and water depth caused more salt water to enter the river mouth, exacerbating the salt intrusion, and the sediment accumulation during the estuary restoration after the tsunami reduced the salinity in the estuary, but with the effect far less dramatic than the effects of the tsunami The expansion of the Natori estuary is not only caused by the tsunami but also caused by a river flood Therefore, a similar salinity intrusion mechanism might also be happened Thus, the findings from this study will be very useful for the river authority to find the best countermeasure plans for the sustainability development of the fishery activities and agricultural purposes in the future Acknowledgements This study supported by the “Tohoku Ecosystem-Associated Marine Sciences (TEAMS)” project funded by MEXT References [1] Jassby, A D., Kimmerer, W J., Monismith, S G., Armor, C., Cloern, J E., Powell, T M., Schubel, J R., Vendlinski, T J (1995) Isohaline position as a habitat indicator for estuarine populations Ecological Applications, 5(1):272–289 [2] Lewis, R E., Uncles, R J (2003) Factors affecting longitudinal dispersion in estuaries of different scale Ocean Dynamics, 53(3):197–207 [3] Ito, K., Katayama, A., Shizuka, K., Monna, N (2016) Effects of the Great East Japan Tsunami on fish populations and ecosystem recovery The Natori River; northeastern Japan In The Natori River; Northeastern Japan Tsunamis and Earthquakes in Coastal Environments, Springer, 201–216 [4] Ha, T D., Hien, D T T., Hoa, N Q., Tinh, N T H (2017) Brackish water treatment research in pilot scale using dual-stage nano filtration for domestic/drinking water supply in Thu Bon river basin Journal of Science and Technology in Civil Engineering (STCE)-NUCE, 11(6):149–155 [5] Bowen, M M., Geyer, W R (2003) Salt transport and the time-dependent salt balance of a partially stratified estuary Journal of Geophysical Research: Oceans, 108(C5) [6] Banas, N S., Hickey, B M., MacCready, P., Newton, J A (2004) Dynamics of Willapa Bay, Washington: A highly unsteady, partially mixed estuary Journal of Physical Oceanography, 34(11):2413–2427 15 Tinh, N X., et al / Journal of Science and Technology in Civil Engineering [7] Uncles, R J., Stephens, J A (1990) Computed and observed currents, elevations, and salinity in a branching estuary Estuaries, 13(2):133–144 [8] Prandle, D (2004) Saline intrusion in partially mixed estuaries Estuarine, Coastal and Shelf Science, 59(3):385–397 [9] Gay, P S., O’Donnell, J (2007) A simple advection-dispersion model for the salt distribution in linearly tapered estuaries Journal of Geophysical Research: Oceans, 112(C7) [10] Ralston, D K., Geyer, W R., Lerczak, J A (2008) Subtidal salinity and velocity in the Hudson River estuary: Observations and modeling Journal of Physical Oceanography, 38(4):753–770 [11] Tanaka, H., Tinh, N X., Umeda, M., Hirao, R., Pradjoko, E., Mano, A., Udo, K (2012) Coastal and estuarine morphology changes induced by the 2011 Great East Japan Earthquake Tsunami Coastal Engineering Journal, 54(01):1250010 [12] Roh, M., Mitobe, Y., Tanaka, H (2016) Morphological Characteristics of River Mouths After the 2011 Tohoku Tsunami in Miyagi Prefecture In Tsunamis and Earthquakes in Coastal Environments, Springer, 137–152 [13] Watanabe, K., Shoji, M., Sasaki, K (2013) Impact on the bivalve Fisheries in the middle-south area of Sendai Bay brought by the Great East Japan Earthquake Miyagi Pref Res Fish Sci., 13:23–29 [14] Japan Meteorological Agency (JMA) http://www.jma.go.jp/jma/indexe.html Website for downloading the river discharge, water level, and tidal level data [15] DSI (2017) The Environmental Fluid Dynamics Code: Theoretical & Computational Aspects of EFDC+ Dynamic Solutions – International, LLC, Edmonds, WA, USA [16] Zhou, J., Falconer, R A., Lin, B (2014) Refinements to the EFDC model for predicting the hydroenvironmental impacts of a barrage across the Severn Estuary Renewable Energy, 62:490–505 [17] Gong, W., Shen, J (2011) The response of salt intrusion to changes in river discharge and tidal mixing during the dry season in the Modaomen Estuary, China Continental Shelf Research, 31(7-8):769–788 [18] Yoon, B I., Woo, S.-B (2015) The along-channel salinity distribution and its response to river discharge in tidally-dominated Han River Estuary, South Korea Procedia Engineering, 116:763–770 [19] Hamrick, J M (1992) A three-dimensional environmental fluid dynamics computer code: Theoretical and computational aspects Special Report in Applied Marine Science and Ocean Engineering No 317 College of William and Mary, VIMS 63 pp [20] Mellor, G L., Yamada, T (1982) Development of a turbulence closure model for geophysical fluid problems Reviews of Geophysics, 20(4):851–875 [21] Liu, C., Yu, M., Jia, L., Cai, H., Chen, X (2019) Impacts of physical alterations on salt transport during the dry season in the Modaomen Estuary, Pearl River Delta, China Estuarine, Coastal and Shelf Science, 227:106345 16 ... due river mouth morphological 361in of ofriver riverflow, flow, mainly duetotothe river mouth morphological changes Underhigh highand the vertical stratification of salinity inthe the Natori River. .. photographs of Natori the Natori morphological after the Figure Aerial photographs of the estuaryestuary morphological changes afterchanges the 2011 tsunami 2011 tsunami Because of the Great Tsunami. .. tsunamiand and 385 analysis by tsunami the topographic subsidence caused by the tsunami and the severe erosion of the beach near the estuary 386 the thesevere severeerosion erosionofofthe thebeach

Ngày đăng: 20/09/2020, 20:44

TỪ KHÓA LIÊN QUAN

TÀI LIỆU CÙNG NGƯỜI DÙNG

TÀI LIỆU LIÊN QUAN