1. 1. GUIDED BY :- PROF. S. G. ADHAU PRESENTED BY :- NISHAD A. WANKHADE DEPARTMENT OF CIVIL ENGINEERING,
2. 2. Introduction Beach nourishment also referred to as beach restoration or beach replenishment describes a process by which sediment (usually sand) lost through erosion is replaced from sources outside of the eroding beach. A wider beach can reduce storm damage to coastal structures by dissipating energy across the surf zone, protecting upland structures and infrastructure from storm surges, tsunamis and unusually high tides. Nourishment is typically a repetitive process, since it does not remove the physical forces that cause erosion, but simply mitigates their effects
3. 3. The first nourishment project in the U.S. was at Coney Island, New York in 1922-23 and is now a common shore protection measure utilized . Nourishment gained popularity because it preserved beach resources , widens the beach , and protects the shore from floods . Nourishment creates a soft (i.e., non-permanent) structure by creating a larger sand reservoir, pushing the shoreline seaward . Hence , people get to use beach as a recreational purposes .
4. 4. Why it is necessary ? More than 70% of Earth's shorelines are retreating due to rising sea levels. As shorelines move landward, structures located on or near the beach may be in danger because floods or tsunamis will have more severe effect and they will be destroyed. In addition , beaches may not seem attractive to people and hence , communities may lose significant amounts of income if they lose the use of their beaches
5. 5. For a good nourishment , the purpose of the nourishment has to be clearly defined. In general, there are three reasons for beach nourishment: 1. combatting coastal erosion (chronic erosion) 2. preventing flooding (safety) 3. maintaining a wide recreational beach.
6. 6. Causes of erosion Beaches can erode both naturally and due to human intervention . Erosion is a natural response to storm activity. Some beaches do not have enough sand available to coastal processes to respond naturally to storms. When there is not enough sand left available on a beach, then there is no recovery of the beach following storms. Many areas of high erosion are due to human activities. Reasons can include , coastal structures like ports and harbors that prevent longshore transport, dams and other river management structures.
7. 7. Requirements for effective nourishment Sediment texture (grain size and sorting) is critical for success. Sand fill must be compatible with native beach sand. In some cases, beaches have been nourished using a finer sand than the original . Monitoring reveals that storms can erode such beaches far more quickly than the natural beach . Projects that did not match grain sizes performed relatively poorly. Nourishment sand that is only slightly smaller than native sand can result in significantly narrower equilibrated dry beach widths compared to sand the same size as native sand.
8. 8. Evaluating material fit requires a sand survey that usually includes geophysical profiles and surface and core sample . This was observed at the Waikiki nourishment project in Hawii . The selection of suitable material for a particular project depends upon the design needs, environmental factors, transport costs considering both short and long-term implications.
9. 9. How Beach Nourishment works - During a beach nourishment project , a large volume of beach-quality sand , called beach fill, are added from outside sources to restore an eroding beach . or a beach where only a small beach , or beach existed . Ultimately, beach nourishment widens a beach and advances the shoreline seaward . Beach nourishment projects are designed and engineered to work like natural beaches , allowing sand to shift continuously in response to changing waves and water levels .
10. 10. This sand once placed gets redistributed gradually by natural processes . Ultimately , the wider , nourished beach , which slopes gently downward below the shore by acting as naturally protective buffers . Engineers may decide to place the beach fill as 1] directly on the beach ,also called as profile nourishment , 2] or as dunes also known as dune nourishment .
11. 11. Profile Nourishment Beach Profile Nourishment describes programs that nourish the full beach profile. In this instance, "profile" means the slope of the uneroded beach from above the water to well out to sea, not just the visible portion. The Gold Coast profile nourishment program placed 75% of its total sand volume below low water level.
12. 12. Profile Nourishment
13. 13. Dune Nourishment Dune nourishment is particularly effective in protecting upland development against storm waves. The placement of material high above the waterline does not expand the width of the dry beach, However, and therefore is not appropriate when the enhancement of recreational opportunities is an important project objective
14. 14. Dune Nourishment
15. 15. Before Nourishment After Nourishment
16. 16. Advantages : 1. It widens the bed 2. Structures behind beach are protected as long as the added sand remains. 3. Most importantly, beach nourishment reduces the detrimental impacts of coastal erosion by providing additional sediment which satisfies erosional forces.
17. 17. DISADVANTAGES : 1.Beach nourishment sand may erode . 2.Beach nourishment is expensive, and must be repeated periodically. 3.The beach turns into a construction zone during nourishment.
18. 18. Alternatives to nourishment Nourishment is not the only technique used to address eroding beaches. Others can be used singly or in combination with nourishment, considering economic, environmental conditions Structural approach is one alternative to nourishment . It is divided into two types :- 1) Hard structures , which includes , wood and rock groins, seawalls, revetments and breakwaters . 2) Soft structures , which includes sand bags ,geotubes ,planting vegetation .
19. 19. Seawalls :- Seawalls are normally constructed of rock and concrete . Seawalls protect property and infrastructure from wave assault . Results in no sandy beach and requires long- term maintenance .
20. 20. Groines :- It runs perpendicular to the shore . It lowers or breaks the energy of wave . Thus it prevent the shore from erosion .
21. 21. Soft Structures Sand Bags Sand bags are kept one on another as shown in figure . They are more of a temporary emergency feature
22. 22. Geo-tubes :- Geotubes consists of sacks made by geotextile that are filled with sand or gravel . Geotubes are more durable emergency protection features which serve as dune cores . . This anchors the sand and sediment,It is not recommended for continuous exposure to high wave energy environments . Planting Vegetation :- This is also called as soft stabilization , because it does not use a structure . This anchors the sand and sediment, which slows erosion caused by wind and waves. Because these methods use only organic materials, the aesthetics and natural habitats of the beach are maintained .
23. 23. Beachface Dewatering Beachface dewatering basically consists of continuously pumping water away from the beachface. Wet beaches tend to lose sand. Waves infiltrate dry beaches easily and deposit sandy sediment. Beach drainage (beach dewatering) uses Pressure Equalizing Modules (PEMs) allow the beach to drain more effectively during tide. Fewer hours of wet beach translate to less erosion. Permeable PEM tubes inserted vertically into the foreshore connect the different layers of groundwater. The groundwater enters the PEM tube allowing gravity to conduct it to a coarser sand layer, where it can drain more quickly .
24. 24. New techniques Rainbowing technique - Rainbowing technique is getting famous nowadays . In rainbowing technique , sand from the nearby seabed , and discharges the sand to needed shore . The process of rainbowing begins with the excavation of sediment, typically sand, from the seabed by a dredger. Dredgers excavate the sediment using mechanical or hydraulic methods or a combination of both. The methodology for beach nourishment by Rainbowing technique was prepared jointly by DCI and Vizag Port. It consists of filling up the hopper with sand by stationary dredging in the new sand trap area. The dredger would hold her positionat this point and discharge the mixture to a distance of approx 100 m so that the material falls within the shore zone .
25. 25. On completion of the discharge within about 1.5 hrs the dredger returns to the new sand trap area and positions for the next load. At least 5 loads were pumped every day with cumulative quantities ranging from 20000 22000 cu.m. per day. Direct Rainbowing onto the beach resulted in savings in time due to reduced discharge time and time loss on account of positioning with anchors. There is also an advantage of pumping in locations with greater erosion selectively. Further, there has been no disruption to container shipping or idle time of the dredger.
26. 26. Costs Nourishment is typically a repetitive process, since nourishment does not remove the physical forces that cause erosion; it simply mitigates their effects. A benign environment increases the interval between nourishment projects, reducing costs. Conversely, high erosion rates may render nourishment financially impractical In many coastal areas, the economic impacts of a wide beach can be substantial. The 10 miles (16 km)long shoreline fronting Miami Beach, Florida was replenished over the period 19761981. The project cost approximately $64,000,000 and revitalized the area's economy.
27. 27. Conclusion After considering all the aspects of beach nourishment , we came to know some important things .Beach nourishment is not permanent solution for eroding beaches . It is very costly and have some demerits and some environmental issues . Whereas, The soft stabilizing methods like sand bags , geotubes , planting vegetation dont have any adverse effect on environment . But they dont restore the eroded beach , they just prevent the beach from further erosion . On the other hand ,beach nourishment has been very successful , even on highly eroded beaches . Nourishment provides us with widened beach that used for various recreational purposes . Even if it is somewhat costly , it proved to be very useful . After studying various aspects , I would conclude that BEACH NOURISHMENT is very beneficial and to protect and restore our beautiful beaches it is the best option .
28. 28. References :- www.wikipedia.com Beach stabilization :-structure & beach nourishment alternatives .(Paper presented by Steven Hafner ) Beach and Dune Restoration by Karl Nordstrom (Book) www.beachapedia.com
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