Why coastal defense structures are used?

1. Why coastal defense structures are used? • To prevent shoreline erosion and flooding of the hinterland. • To shelter harbor basins and harbor entrances against waves. • To stabilize of nevigation channels at inlets. • To protect of water intakes and outfalls • To retain or rebuild natural sytems(cliffs, dunes) or protect mans artifacts(buildings) landward of the shoreline.

2. What kinds of conditions should be taken into? • Stability • Safety • Serviceability • Economy

3. PLANNING DESIGN: Nature vs Man on coastal defense

4. PLANNING DESIGN: Hard Shoreline Protection Structures

5. PLANNING DESIGN: • Groinsare structures built out from the shoreline to trap sand in the longshore drift. • Breakwatersare built offshore, parallel to the coast. The purpose of a breakwater is to lessen the impact of waves on the shore, much like a natural reef, and it need not protrude from the water to do so. • A tombolo is a sand spit that forms between the beach and a breakwater. A groin and a breakwater are sometimes combined into a T shaped structure. • A jetty is much larger than a groin, and is built to stabilize an inlet or other coastal feature rather than to capture sand.

6. PLANNING DESIGN: Hard and Soft Shoreline Protection Structures

7. PLANNING DESIGN: • A sand hoft is an offshore island created by the accumulation of sand around an old jetty that is no longer attached to the land due to shoreline retreat. These can have a stabilizing effect on the beach in much the same way abreakwaters and natural barrier islands. • Aseawall is an onshore construction used when erosion is so great that there is no beach left. Seawalls are large heavy structures that face the sea, while bulkheads are lighter structures built in protected areas.

8. Breakwaters: The breakwaters are generally classified in two types. • Shore-connected Breakwaters: Acts as an total littoral drift barrier in the surf zone. The accretion extends along the seaward face of breakwater building a berm. Erosion starts from the other side of the shore • Off-shore Breakwaters: Off-shore Breakwaters provides protection from wave action to a area or shoreline located on the leeward side of the structure. Offshore breakwaters are usually orients approximately parallel to shore and also serve as a littoral barrier sediment trap.

9. Breakwaters: The types of breakwaters according to their construction methodology and dimensional and material characteristrics are listed below. A) Reef Breakwaters B) Floating Breakwaters C) Vertical-front breakwaters D) Piled breakwaters E) Rubble Mound Breakwater

11. CHAPTER 6: MITIGATION STRATEGIES

12. Tsunami can not be felt aboard ships nor can they be seen from the air in the open ocean.

13. Learn about : • International Tsunami Information Centre (ITIC) • International Tsunami Warning System (ITWS)

14. http://www.prh.noaa.gov/itic/ • Mandate • Functions • Research and Data CollectionResponsibilities • Visiting Scientists Program • Education, Preparedness & • Disaster Reduction

15. What is the International Tsunami Warning System (ITWS)? • Seismic station • Tide station

16. International Tsunami Warning System (ITWS) • ITWS includes 31 seismic stations & • more than 60 tide stations • The stations have ability to transmit • their data immediately & in real time • to the headquarters at PTWC in • Hawaii.

17. DART SYSTEM • http://www.pmel.noaa.gov/tsunami/Dart/

18. How does the International Tsunami Warning System Work? • Tsunami WARNING & • Tsunami WATCH

19. Mooring System • A DART system consists of a seafloor bottom pressure recording (BPR) system capable of detecting tsunamis as small as 1 cm, and a moored surface buoy for real-time communications. • An acoustic link is used to transmit data from the BPR on the seafloor to the surface buoy. • The data are then relayed via a GOES satellite link to ground stations, which demodulate the signals for immediate dissemination to NOAA's Tsunami Warning Centers and PMEL.

20. USGS-NOAA

21. Surface Buoy • The surface mooring uses a 2.5 m diameter fiberglass over foam disk buoy with a gross displacement of 4000 kg. • The mooring line is 19 mm 8-strand plaited nylon line with a rated breaking strength of 7100 kg and is deployed with a scope of 0.985. • This maintains a tight watch circle to keep the buoy positioned within the narrow cone of the acoustic transmission. • Two downward looking transducers are mounted on the buoy bridle at a depth of 1.5 m below the sea surface. • A multi layered baffle system of steel, lead, and syntactic foam shields the transducers and cushions them with rubber pads for a soft mount.

22. Bottom Package • Consists of a Bottom Pressure Recorder, an acoustic modem, acoustic release unit and battery pack bolted to a platform, to which adisposable anchor, flotation, and recovery aids are attached. • Moorings are designed to free-fall to the bottom and are deployable for 24 months at depths of 6000 m; recovery is initiated by triggering the acoustic release to separate from the anchor, at which point the flotation brings the unit to the surface.

23. Bottom Package These systems have measured tsunamis characterized by amplitudes less than 1 cm in the deep ocean, using a quartz crystal pressure transducer that is sensitive to changes corresponding to less than a millimeter of equivalent sea level change in the tsunami frequency band.

25. Dissemination of Watches & Warnings by ITIC When Earthquake is Strong Enough to Cause a Tsunami !! • Monitoring the tide gauges near the epicenter • Watch bulletins for all earthquake ≥ 7 in the • Aleutian Islands & ≥ 7.5 elsewhere in the Pacific • Watching cancellation: Negligible tsunami • or no tsunami Watching Warning if a tsunami threat

26. No Tsunami Warning Issued at 26 Dec 2004 Disaster !! No Tsunami Warning System exists for the Indian Ocean !!

27. The flooding of an area can extend inland by 1000 feet(305 m) or more, covering large expanses of land with water & debris.

28. Complicated behavior of tsunami waves near the coast ! • The first run-up of a tsunami is • often not the largest. • Do not return to a beach several • hours after a tsunami hits.

29. Are tsunamis so destructive?

30. Be Prepared for Tsunamis & Protect Yourself

31. Be Prepared for Tsunamis & Protect Yourself

32. Tsunami Preparedness • Know the risk. • Plan and practice evacuation routes. • Discuss tsunamis with your family. • Talk to your insurance agent. • Use a NOAA Weather Radio.

33. Similar Tsunamis, Similar Strategies for Survival

34. If a Strong Coastal Earthquake Occurs . . . Drop, cover, and hold until the shaking stops!!

35. Tsunami is coming! What you must do!

36. Tsunami is coming! You are at the shore What you must do!

37. Tsunami is coming! You are at the shore What you must do!

38. If a Tsunami Warning Is Issued • If in a tsunami risk area, evacuate immediately. • Follow instructions issued by local authorities. • Get to higher ground as far inland as possible.

39. After Tsunami Is Gone • Listen to a NOAA Weather Radio or Coast Guard emergency frequency station. • Return home only after local officials tell you that it is safe.

40. Tsunami is coming! What you must do, If you are on a boat!

41. If a Tsunami Warning Is Issued • Do not return to port if you are at sea • Rapid changes in water level causing unpredictable dangerous currents in harbors and ports.

42. If a Tsunami Warning Is Issued • Contact the harbor authority before returning to port making sure to verify that conditions in the harbor are safe for navigation and berthing.