Measuring Historical Coastal Change using GIS and the Change Polygon Approach

Transactions in GISTransactions in GIS, Volume 16, Issue 1, February 2012

Martyn J. Smith and Robert G. Cromley

“This study compares two automated approaches, the transect-from-baseline technique and a new change polygon method, for quantifying historical coastal change over time. The study shows that the transect-from-baseline technique is complicated by choice of a proper baseline as well as generating transects that intersect with each other rather than with the nearest shoreline. The change polygon method captures the full spatial difference between the positions of the two shorelines and average coastal change is the defined as the ratio of the net area divided by the shoreline length.

A change polygon denoting positive and negative areas of change

A change polygon denoting positive and negative areas of change (a red area represents coastline loss due to erosion and a green area represents land gain due to deposition)

“Although then change polygon method is sensitive to the definition and measurement of shoreline length, the results are more invariant to parameter changes than the transect-from-baseline method, suggesting that the change polygon technique may be a more robust coastal change method.”