Vulnerability of the natural coastal system to accelerated sea-level rise, Yap Islands, Federated States of Micronesia; case study preliminary results
Year: 1994
Type: report
Abstract: Yap State in the Federated States of Micronesia consists of 16 islands spread over a distance of nearly 1,000 km across the western Pacific Ocean.Four island types are present in Yap State: 1) The main Yap Islands consist of four large , and several smaller, high volcanic islands surrounded by a fringing reef.2) Ten atolls consisting of an annular reef rim enclosing a central lagoon which may be connected to the open ocean by deep passages.Low-lying coral islets are scattered on the upper surface of the reef rim. 3) There are four Reef Islands, which are low-lying coral islands developed on a small reef platform and devoid of a significant lagoon.4) A single high limestone island (Fais) partially surrounded by a narrow fringing reef and the remainder of the island consisting of a cliffed-coast.The present study concentrated on identifying and describing characteristic shoreline areas of the main Yap Islands.Coastal profile data were from eleven representative sites around the Yap islands shoreline.Three critical natural environments were identified: 1) Mangrove forests which comprise about 10% of the total land area and a distance of nearly 114 km along the shoreline.Mangrove area has been expanding throughout the Holocene and we suggest that under a rising sea level would expand in a landward direction as low-lying coastal land becomes intertidal.Shoreline erosion would probably be minimized due to mangrove protection.2) Sand beaches and associated sand-rich coastal plains are limited in extent, occurring in exposed localities and comprising only about 0.25% of the total land area.However, they form important settlement sites and are critical to modern and traditional Yapese culture.Sand beaches are extremely vulnerable to accelerated erosion and a landward shift of the shoreline profile during a rising sea level can be expected.3) Coral reefs surround the main Yap Islands and are a source of sediment for the beaches and adjacent fringing reefs.Reef response to accelerated sea-level rise is probably one of expanded vertical growth and increased carbonate production as shallow substrates are submerged.Colonia, located near Tamil Harbor on Yap Island in the main Yap Islands, is the center of government and commerce for Yap State.Results of profiling along the Colonia shoreline suggests most of the important roads and buildings lie above predicted accelerated sea-level rise (ASLR) still-water levels (i.e.> 1 m above present MSL).However, storms and tsunamis can be expected to play a greater role in modifying the shoreline under higher sea level.The low-lying atolls and reef islands of Yap State potentially can suffer severe consequences of accelerated sea-level rise.Maximum elevation of these islands is around 7 m and they probably average 3-4 m above MSL.Results from profiling on Falalop Islet in Ulithi Atoll indicates some shoreline erosion (18m maximum) would occur under higher sea level but the islet would probably still be inhabitable.However, there is no higher ground for relocation in the advent of severe land loss due to ASLR mediated erosion.
DOI: 10.3133/ofr94665
Authors: B.M. Richmond, T.E. Reiss
Language: English
Topic: Coastal and Marine Dynamics
Subfield: Earth-Surface Processes
Field: Earth and Planetary Sciences
Domain: Physical Sciences
SDG: Life on land
Open Access status: bronze
OpenAlex ID: W40798013