COASTAL EROSION IN MEKONG DELTA & PROTECTION SOLUTIONS Thong NGUYEN et al. Tel. 098 99 66 719 Email: nthong56@yahoo.fr 7/1/2018 1

Assoc. Prof. Nguyễn Thống Dr. Hồ Tuấn Đức Dr. Lưu Xuân Lộc MSc. Lê Ngọc Anh 7/1/2018 2

Overview & Methodology Region zone Local & study zone CONTENT Overview & Methodology Region zone Local & study zone Results and discussions Perspectives & Conclusion 7/1/2018

1. OVERVIEW & METHODOLOGY 7/1/2018

Research group was involved in: Work package 4.1: Wave calculation in regional and local zone for U Minh, using TOMAWAC module; Work package 4.2: Calculation of coastal currents in regional and local zone for U Minh, using TELEMAC (driven by wind, wave, tide and flow from estuary) 7/1/2018 5

Work package 5.2: Hydrodynamic model for studied area in U Minh Work package 5.1: Simulation of suspension and sediment transport at Mekong Delta’s estuaries and coastal area near Cà Mau-U Minh (TELEMAC + SYSIPHE). Work package 5.2: Hydrodynamic model for studied area in U Minh 7/1/2018 6

Work package 5.3: Understand the erosion process at coastal area of U Minh-Cà Mau by numerical model. Work package 6.2: Evaluate the shore protection works by using TELEMAC + SYSIPHE 7/1/2018 7

METHODOLOGY Numerical model. Hydrodynamic model for southern area of East Sea: Telemac2D + Tomawac (region zone). Hydrodynamic model & morphology for local & study zone: Telemac2d + Tomawac + Sisyphe. 7/1/2018 8

Study zone COASTAL AREA IN THE DOWNSTREAM OF MEKONG RIVER (LMDCZ) 9 7/1/2018 9

(region zone) 2. COASTAL AREA IN THE DOWNSTREAM OF THE MEKONG RIVER 7/1/2018

Study zone: Region zone Vũng Tàu Vĩnh Long Cần Thơ Cà Mau 303000 elements Max = 9km Min = 8m Coastal = 250m 7/1/2018 11

BOUNDARY CONDITIONS East Sea 7/1/2018

Bathymetry & bound. cond. - Coastal: SIWRR - Offshore: ETOPO1 with x=900m. Liquid bound.: Astronomical tide from TPXO with 9 main tides: K1, O1, P1, Q1 , S2, N2, K2, M2 và M4. Wind, wave: Data from NOAA. 7/1/2018

Model calibration & validation 7/1/2018

Wind (1-2014) 7/1/2018

Wind (8-2014) 7/1/2018

Boundary Q1 & Q2 (1-2014) 7/1/2018

Tidal boundary (1-2014) 7/1/2018

Wave boundary HM0 (1-2014) T (ngày) 7/1/2018

Wave boundary HM0 (8-2014) T (ngày) 7/1/2018

TRẦN ĐỀ Tidal (1-1-2014  15-1-2014) 7/1/2018

GÀNH HÀO Tidal (1/1/2014  15/1/2014) 7/1/2018

RẠCH GIÁ Tidal (1/1/2014  15/1/2014) 7/1/2018

Preliminary results Hydrodynamics Wave Sediment transport 7/1/2018

Mean velocity field (1-2014) 7/1/2018

Mean velocity field (8-2014) Site U Minh 7/1/2018

Mean velocity field (8-2014) Local U Minh 7/1/2018 Animation: SIWRR_Hydro.avi

Comments Mean velocity field in January 2014 is quite large comparing to that in August 2014 Formation of coastal currents toward the south during January 2014 Mean currents in August 2014 is minor. 7/1/2018

Wave field HM0 at 12H, 13/1/2014 Vĩnh Long Cần Thơ Cà Mau 7/1/2018

Average wave field HM0 in January 2014 7/1/2018

Wave field HM0 at 24H, 15/8/2014 7/1/2018

Average wave field HM0 in August 2014 7/1/2018 Animation: SIWRR_Wave.avi

Waves in Jan. 2014 tends to be larger than in August 2014. COMMENTS Waves in Jan. 2014 tends to be larger than in August 2014. Waves in the West tends to be intensified by Southwest wind. 7/1/2018

WAVE HM0(t) (1-2014) HM0 (m) T (ngày) 7/1/2018

WAVE HM0(t) (8-2014) 7/1/2018

COMMENTS In Jan. 2014, NorthEast wind is dominant  waves in East Sea are intensified. In Aug. 2014, SouthWest wind is dominant  waves in East Sea are reduced. 7/1/2018

5. RESULTS & PERSPECTIVES 7/1/2018

Southwest winds intensify the waves in the West Sea. CONCLUSIONS Wind direction affects significantly the distribution of wave intensity in the East Sea and West Sea. Southwest winds intensify the waves in the West Sea. The sediment transport rates are important in estuary area and in the main rivers in Mekong. 7/1/2018

In addition to the sediment from the upstream of the Mekong river, the sediment transport due to morphology changes also plays an important role. The coastal erosion / acrreation rate at U Minh is less than in other areas. 7/1/2018

 Hydraulic regime in the West Sea is quite complex. Simulation results and observation are quite different. could be the complexity of bathymetry and tidal conditions. 7/1/2018

Develop the own grid system for U Minh area. WHAT TO DO NEXT ... Develop the own grid system for U Minh area. Simulation for the years with available flow and stage data (2015, 2016). Impact assessment of mangrove and maleleuca fences. 7/1/2018

Update and complete the coastal bathymetry. WHAT TO DO NEXT ... Update and complete the coastal bathymetry. Simulation of shore protection works: semi-submerged groyne. 7/1/2018

THANK YOU for your attention! 7/1/2018