Atoll Rim Expansion or Erosion in Diego Garcia Atoll, Indian Ocean? Comment on Hamylton, S.; East, H. A Geospatial Appraisal of Ecological and Geomorphic Change on Diego Garcia Atoll, Chagos Islands (British Indian Ocean Territory). Remote Sens. 2012, 4, 3444–3461

Charles Sheppard

doi:10.3390/rs6032463

Abstract

Hamylton and East [1] reported a remarkably substantial expansion and accretion of land since the 1960s at numerous sites along the island of Diego Garcia atoll. This atoll has a near continuous rim encircling its lagoon, and they reported that the width of the island rim has expanded by several tens of metres in many places. Those results contrast markedly with my own near-annual observations on the ground where erosion and increased seawater inundation, rather than land accretion, is evident in many places. Hamylton and East have never visited the atoll but their results have been picked up for various reasons. Therefore I note possible reasons for the substantial discrepancy between their measurements and my own observations, and propose a resolution.

Highlights

1960s at numerous sites along the island of Diego Garcia atoll. This atoll has a near continuous rim encircling its lagoon, and they reported that the width of the island rim has expanded by several tens of metres in many places
The thickness of the pencil line drawing the coastline in the journal figure represents more than 30 metres, which is more than some of their claimed coastal changes of many metres
The satellite map used in the later image is at a more appropriate, finer scale

Summary

Introduction

1960s at numerous sites along the island of Diego Garcia atoll. This atoll has a near continuous rim encircling its lagoon, and they reported that the width of the island rim has expanded by several tens of metres in many places. Hamylton and East [1] reported a remarkably substantial expansion and accretion of land since the 1960s at numerous sites along the island of Diego Garcia atoll.

Results

Conclusion