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[B-10.4 Deformation of Barrier Islands due to Sea Level Rise and Barrier Preservation(Final Report)]

[Contact Person]

Shigenobu Tanaka^* and Koji Yamamoto^**
*Head, ^**Research Engineer
Coastal Engineering Division
River Department
Public Works Research Institute
Ministry of Construction
Asahi 1, Tsukuba, Ibaraki, 305 Japan
Tel: +81-298-64-2327 Fax: +81-298-64-1168

[Total Budget for FY1993-FY1995]

10,077,000Yen(FY1995; 2,909,000Yen)

[Abstract]

(1) CSIRO(1992) estimated that the sea level rise would be 15-90cm in 2070. Since sea level seems to rise faster than expected, sea level rise rate was estimated to become 0.15-0.75 cm/year in 2010 and 0.18-1.01 cm/year in 2070.
(2) It was found that the distribution of barriers are global. Because the barrier has a lagoon, which is precious environment and is utilized for navigation etc., it can be said that the barrier is one of the characteristic landforms that should be conserved.
(3) A hydraulic experiment on 1/100 seabed slope showed following; Under the condition of fluctuating water level and wave height, several large-scale bars may be formed due to sectional coastal process. The large- scale bar closest to shore may become a barrier with a lagoon if the water level settle abruptly.
(4) A hydraulic experiment focusing on the deformation of barrier showed that the barrier moves toward the land as the water level rises.
(5) It was suggested for the countermeasure against extinction of barrier due to the sea level rise that widening barrier by beach nourishment is effective.
In case that a coastal structure cuts the littoral drift, sand bypassing is also effective. Furthermore, these countermeasures should be appreciated because they use built-in beach stabilizing mechanism of nature.

[Key Words]

sea level rise, barrier, Lagoon, barrier formation process, countermeasure.