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# Sediment transport-Environmental Health

## on Oct 29, 2013

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• The distance from shoreline is 200 m. The water depth in the basin range from 5 to 7 m.
• The computations were performed on an area of 0.6 km alongshore and 0.8 km cross-shore. The length of the detached breakwater was 300 m, 3.0 m crown depth, and the distance from shoreline is 150 m.
• The computations were performed on an area of 0.6 km alongshore and 0.8 km cross-shore. The length of the submerged breakwater was 300 m, 2.0 m crown depth, and the distance from shoreline is 200 m.
• The computations were performed on an area of 0.6 km alongshore and 0.8 km cross-shore. The length of the groin was 150 m and 300 m spacing.

## Sediment transport-Environmental HealthPresentation Transcript

• Sediment transport and Coastal LOGO erosion Al-Azhar University-Gaza Master Program of Water and Environmental Science
• Contents 1 Introduction 2 Study Area 3 Materials & Methods 4 Results & Discussion 5 Conclusions 2
• Mediterranean Sea 1900 1964 00 19 64 19 1971 71 19 88 19 90 19 91 19 1988 96 19 00 20 1990 1991 Rosetta Promontory 1996 2000 Nile River 3 3
• 1. Introduction 1 2 3 Most sediments coming to Gaza are originally from Nile River and it is about 350,000 cubic meter annually (Perlin and Kit, 1999) Construction of the low Aswan dam in 1902 and the high Aswan dam in 1964 has almost completely interrupted the Nile River sediment discharge to the sea (Inman et al, 1976) Bardawil lagoon sandbar and Delta continue to act as a significant source and supplier of sand to Gaza coast (Inman et al, 1976) 4
• 1. Introduction 5
• 1. Introduction  Alongshore sediment transport can calculate using the following expressions:  CERC expression (1)  Kamphuis expression (2) where Hb = breaking wave height, mb = seabed slop, D50 = characteristic rock diameter, αb = breaking wave angle. 6
• 1. Introduction Annual bulk sediment transport rates for Gaza beach (idku) Wave Scenarios Hs (m) Ts (Sec) a0 (Deg) Hb (m) H ≤ 1.0m 1.0 < H ≤ 2.0 2.0 < H ≤ 3.0 3.0 < H ≤ 4.0 H > 4.0m 0.5 1.3 2.4 3.4 4.2 6.3 7.1 8.0 8.8 9.4 26 15 17 18 5 0.62 1.46 2.53 3.49 4.32 ab (Deg) 8 6 8 9 3 Total Duration Sediment, m3/year (d) 289 63 10 2.7 0.3 365 60,746 73,404 48,851 31,050 3,078 220,000 7
• 1. Introduction Annual bulk sediment transport rates for Gaza beach (Ashdoud) Wave Scenarios Hs (m) Ts sec) a0 deg) H ≤ 1.0m 1.0 < H ≤ 2.0 2.0 < H ≤ 3.0 3.0 < H ≤ 4.0 H > 4.0m 0.67 1 2.25 3.5 3.55 5.9 6.5 7.9 8.8 8.8 -32 35 -13 20 41.2 Hb m) ab Duration Sediment m3/year deg) days Total 197.10 159.86 1.80 3.32 2.92 365 - 65,374 137,138 - 4,807 43,033 47,139 160,000 8
• 1. Introduction Sediment transport The amount of sediment transported along shore 170,000 to 540,000 .(Shoshana G., 2000) Types of sediment transport 1- Cross shore 9
• 1. Introduction Sediment transport 2- Alongshore 10
• 1. Introduction In recent decades, the coast of Gaza has been plagued by a serious shortage of sand and by erosion 11
• 1. Introduction The coast of Gaza was affected by man-made structures prior to the fishing harbour (Zviely and Klein, 2003) 4 In 1972 two groins, 120m long each 500m apart 12
• 1. Introduction 5 The erosion was controlled by a series of nine detached breakwaters built in 1978 The detached breakwaters, 50-120 m long, were built 50 m from the coast line at a depth of 1 m 13
• 1. Introduction 6 In 1994, the construction of Gaza fishing harbor started and completed in 1998. The construction negatively increase the erosion rates The fishing harbor extends some 500m into the sea, enabling access to vessels up to 6m deep. 14
• 2. Study Area The study covers an area extended from Wadi Gaza up to 3km north the Gaza fishing harbour 15
• Gaza harbor 16
• 17
• 18
• 3. Materials and Methods  Data were collected from analyses of Landsat images from 1972 to 2010 and combined with sample collection for grain size analyses in order to study the shoreline change  Numerical model runs to predict the morphodynamics around the mitigation structures were carried out 19
• 3. Materials and Methods 3.1 Satellite images The infrared band was selected for the subsequent image processing. The image processing procedures were carried out using ERDAS Imagine and ArcGIS Image source Date Landsat 1 MSS Landsat 5 MSS Landsat 5 TM Landsat 5 TM Landsat 7 ETM+ 29-06-1972 14-05-1984 29-05-1998 29-03-2003 04-06-2010 Resolution [m m] 60.0 60.0 60.0 60.0 30.0 30.0 30.0 30.0 30.0 30.0 20
• 3. Materials and Methods 3.2 Numerical model The relocation of fishing harbor to offshore, groins field system, detached breakwaters and wide-crested submerged breakwaters were suggested and examined using the morphodynamic numerical model of nearshore waves, currents, and sediment transport in order to mitigate the coastal erosion (Seif et al., 2011) 21
• 4. Results and Discussion 4.1 Remote sensing findings The impact has extended to about 2.5km to north and to south the harbor The waterline advanced at the south of harbor by 0.75 m year-1 and treated at the north of harbor by 1.15 m year-1 Accretion and erosion rates for the study area Erosion Image period area ×103 Accretion rate ×103 area ×103 rate ×103 [m2] 1972-1984 1984-1998 1998-2003 2003-2010 Total [m2 year-1] [m2] [m2 year-1] 180 200 8 143 531 15 14 2 20 14 122 224 190 70 606 10 16 38 10 16 22
• 4. Results and Discussion 4.2 Sediment transport rates  The net annual rate of wave-induced alongshore sediment transport range from minimum 160×103 to maximum 220×103 m3, and the average annual rate of 190×103 m3, northward  The sand volume of accretion was estimated 80×103 m3 per year 23
• 4. Results and Discussion 4.3 Numerical model results Offshore fishing harbor model test 4.2 4 3.8 3.6 3.4 3.2 3 0 00 0 0 0 00 0 00 0 200 2.8 400 X(m ) 2.6 600 800 1.4 1.2 0.21.4 0 0.6 0.4 0.8 1.2 1 2.2 1.8 2 1.6 1.8 2.4 2.2 2 00 0.2 0.4 1 0.8 200 2.8 0 1.6 2.4 N 400 2.6 X(m) 0 0.2 0.4 0.6 0.6 0 1 0.8 800 1.4 1.2 1m/s Unit: m 1000 0 1000 0 200 400 600 800 0 1000 200 400 200 7 6 6 5 5 5 5 5 400 X(m ) X(m ) 5 600 5 600 4 3 1 800 5 4 3 3 2 2 N 1000 8 7 400 800 0 8 200 600 Y(m) Y(m ) 0 600 1 800 0 0 Unit: m Unit: m -1 1000 0 200 400 600 Y(m ) -1 1000 800 1000 0 200 400 600 Y(m ) 24 800 1000
• 25
• 4. Results and Discussion 4.3 Numerical model results N 0 200 4.2 4 3.8 3.6 3.4 3.2 3 2.8 2.6 2.4 2.2 2 1.8 1.6 1.4 1.2 1 0.8 0.6 400 400 X(m) X(m ) 200 0 600 600 0.4 0.2 800 1m/s 800 100 200 14 300 400 Y(m ) 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 -1 200 400 600 800 0 100 200 300 400 Y(m ) 500 0 600 0 200 400 600 Y(m) 14 14 13 12 11 10 9 8 7 6 200 X(m ) 0 0.2 0.4 Unit: m 0 0 0 X(m ) Detached breakwater model test 400 5 4 3 2 1 0 -1 600 Unit: m 500 600 800 0 100 200 300 400 Y(m ) 5 Unit: 26 m600 500
• 4. Results and Discussion 4.3 Numerical model results N 0 200 400 400 X(m) m X( ) 200 1.4 1.4 600 600 1.4 1.2 1 0.8 0.6 0.4 0.2 1m/s 0 800 100 200 14 300 400 Y(m ) 14 13 12 11 10 9 8 7 6 5 4 200 400 3 2 1 0 -1 600 800 0 100 200 300 400 Y(m ) 500 800 0 600 200 400 600 Y(m) 0 14 14 13 12 11 10 9 8 7 6 5 200 m X( ) 0 Unit: m 0 0 m X( ) Submerged breakwaters model test 400 4 2 3 3 2 3 600 1 0 Unit: m 500 600 2 -1 800 0 100 200 300 400 Y(m ) Unit: m 500 27 600
• 4. Results and Discussion 4.3 Numerical model results N 0 200 4.2 600 0 800 0 0 0 100 200 14 300 400 Y(m ) 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 -1 200 400 600 800 0 100 200 300 400 Y(m ) 400 X(m) 400 4 3.8 3.6 3.4 3.2 3 2.8 2.6 2.4 2.2 2 1.8 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 600 1m/s Unit: m 500 800 0 600 200 400 600 Y(m) 0 14 14 13 12 11 10 9 8 7 6 200 X(m ) X(m ) 200 X(m ) Groins field system model test 400 5 4 3 600 Unit: m 500 600 2 1 0 -1 800 0 100 200 300 400 Y(m ) Unit: m 28 500 600
• 4. Results and Discussion 4.3 Numerical model results Environmental impact of various mitigation alternatives Mitigation alternative Annual rate [m3 km-1] Relocation of harbor Detached BW Submersed BW Groins field system + 4×103 ‒23×103 +28×103 ‒22×103 Remarks Accretion Erosion Accretion Erosion 29
• 5. Conclusions  The erosion problem along Gaza beach is due to the man-made structures as confirmed by analyzing the historical satellite images from 1972 to 2010  The numerical model results show that the offshore harbor is the best alternative for Gaza beach restoration  Alternatively, the wide-crested submerged breakwater, “artificial reef”, is an effective structure for preventing sandy beach erosion 30
• References  Mazen Abualtayef, Ahmed Abu Foul, Ahmed Khaled Seif, Abdel Fattah Abd Rabou, Omar Matar, Rashad Alhourani, Samir Matar, and Ibrahim Alshiekh. Mitigation measures for Gaza caostal erosion. 4th International Engineering Conference, Islamic University of Gaza, Gaza, Palestine, pp 1-13, October 15-16, 2012  Ahmed Seif. Numerical simulation of 3D morphodynamic around coastal structures using quasi-3D nearshore current model. Doctorate thesis, Tottori university, 2011.  Ahmed Seif, Masamitsu Kuroiwa, Mazen Abualtayef, Hajime Mase, Yuhei Matsubara. A hydrodynamic model of nearshore waves and wave-induced currents. Inter. J. Nav. Archit. Oc. Engng, 3(3), 216-224, 2011.  Burcharth H, Hawkins S, Zanuttigh B, Lamberti A. Environmental design guidelines for low crested coastal structures, 2007.  Lee E. Harris, Ph.D., P.E. Investigations and recommendations for solutions to the beach erosion problems in the city of Herzliya, Israel, 2007. 31
• References  Dov Zviely and Micha Klein. The environmental impact of the Gaza Strip coastal constructions. Journal of coastal research, 19(4), 1122-1127, 2003.  M. A. Azab and A. M. Noor. Change detection of the North Sinai coast by using remote sensing and geographic information system, 2003.  Palestinian National Authority, Ministry of Environmental affairs. Gaza Coastal and Marine Environmental Protection and Management Action Plan, 2000. 32
• LOGO Mrbakr1991@gmail.com 33