Why coastal defense structures are used?

1. To prevent shoreline erosion and flooding of the hinterland.

2. To shelter harbor basins and harbor entrances against waves.

3. To stabilize of nevigation channels at inlets.4. To protect of water intakes and outfalls5. To retain or rebuild natural sytems(cliffs,

dunes) or protect mans artifacts(buildings) landward of the shoreline.

What kinds of conditions should be taken into?

1. Stability

2. Safety

3. Serviceability

4. Economy

COASTAL PROTECTION BY

NATURE

COASTAL PROTECTION BYMAN

SHORE ROCK SEA WALL

ROCK REEF SUBMERGED BREAKWATER

ROCK ISLAND OFFSHORE BREAKWATER

HEADLAND HEADLAND BREAKWATER

ROCK PERPENDICULAR TO SHORELINE GROINS

SEA FLOOR VEGETATION BOTTOM MATTRESS

DUNE DYKE

MATERIALS TRANSFER TO SHORE BY:WIND DRIFT RIVERS LONGSHORE LITTORAL DRIFT

ARTIFICIAL NOURISHMENT FROM LAND SOURCES

SEA BOTTOM TRANSFER ARTIFICIAL NOURISHMENT FROM OFFSHORE SOURCES

PLANNING DESIGN:PLANNING DESIGN:

Nature vs Man on coastal defenseNature vs Man on coastal defense

PLANNING DESIGN:

Hard Shoreline Protection StructuresHard Shoreline Protection Structures

PLANNING DESIGN:• Groins are structures built out from the shoreline to

trap sand in the longshore drift.• Breakwaters are 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.

PLANNING DESIGN:

Hard and Soft Shoreline Protection StructuresHard and Soft Shoreline Protection Structures

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 a breakwaters and natural barrier islands.

• A seawall 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.

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.

Breakwaters:

The types of breakwaters according to their constructionmethodology and dimensional and material characteristricsare listed below.

A) Reef Breakwaters

B) Floating Breakwaters

C) Vertical-front breakwaters

D) Piled breakwaters

E) Rubble Mound Breakwater

CLASSIFICATION OF COASTAL PROTECTION CONCERNS &SOLUTIONS TO THEM

SHORELINE

STABILIZATION

BACKSHORE

PROTECTION

HARBOR

PROTECTION

INLET

STABILIZATION

SEAWALL

BULKHEAD

REVETMENT

GROIN

DETACHED BREAKWATER

BEACH NOURISHME

NTSAND

BYPASSINGAT INLET

SEAWALL

PROTECTIVE BEACH

JETTIES

SHORE-CONNECTED

BREAKWATERS

OFFSHORE BREAKWATER

S

JETTIES

DREDGING

CONSIDERATIONSHydraulicsSedimentation Control StructureMaintenanceLegal RequirementsEnvironmentEconomicsNavigation( for

harbor pro. and inlet stabil.)

SAND DUNE

REVETMENT

BULKHEAD

CHAPTER 6: MITIGATION STRATEGIES

Tsunami can not be felt

aboard ships nor can they be

seen from the air in the open

ocean.

Learn about :

• International Tsunami Information Centre (ITIC)

• International Tsunami Warning System (ITWS)

• Mandate

• Functions

• Research and Data Collection Responsibilities

• Visiting Scientists Program

• Education, Preparedness &Disaster Reduction

http://www.prh.noaa.gov/itic/

What is the International Tsunami

Warning System (ITWS)?

• Seismic station

• Tide station

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.

DART SYSTEM

• http://www.pmel.noaa.gov/tsunami/Dart/

How does the International Tsunami Warning System

Work?

• Tsunami WARNING

&

• Tsunami WATCH

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.

USGS-NOAA

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.

Bottom Package• Consists of a Bottom Pressure Recorder, an acoustic modem,

acoustic release unit and battery pack bolted to a platform, to which a disposable 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.

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.

Bottom Package

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

No Tsunami Warning

Issued at 26 Dec 2004

Disaster !!

No Tsunami Warning System exists for the Indian

Ocean !!

The flooding of an area can extend

inland by 1000 feet (305 m) or

more, covering large expanses

of land with water

& debris.

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.

Are tsunamis so destructive?

Be Prepared for Tsunamis

& Protect Yourself

Be Prepared for Tsunamis

& Protect Yourself

Be Prepared for Tsunamis

& Protect Yourself

Be Prepared for Tsunamis

& Protect Yourself

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.

Similar Tsunamis, Similar Strategies for

Survival

If a Strong Coastal Earthquake Occurs . . .

Drop, cover, and hold until the shaking stops!!

What you must do!

Tsunami is coming!

What you must do!

Tsunami is coming!

You are at the shore

What you must do!

Tsunami is coming!

You are at the shore

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.

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.

What you must do,

If you are on a boat!

Tsunami is coming!

• Do not return to port if you are at sea

• Rapid changes in water level causing unpredictable dangerous currents in harbors and ports.

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.

If a Tsunami Warning Is Issued