National assessment of shoreline change: Historical shoreline change in the Hawaiian Islands

Abstract

For more information on the USGS-the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment, visit http://www.usgs.gov or call 1-888-ASK-USGS.For an overview of USGS information products, including maps, imagery, and publications, visit http://www.usgs.gov/pubprodTo order this and other USGS information products, visit http://store.usgs.gov Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.Although this report is in the public domain, permission must be secured from the individual copyright owners to reproduce any copyrighted materials contained within this report. Executive SummaryBeach erosion is a chronic problem along most open-ocean shores of the United States. As coastal populations expand and community infrastructure comes under increasing threat from erosion, there is a demand for accurate information about trends and rates of shoreline movement, as well as a need for a comprehensive analysis of shoreline movement that is consistent from one coastal region to another. To meet these national needs, the U.S. Geological Survey began an analysis to document historical shoreline change along open-ocean sandy shores of the conterminous United States and parts of Hawaii and Alaska. An additional purpose of this work is to develop systematic methodology for mapping and analyzing shoreline movement so that consistent periodic updates regarding coastal erosion can be made nationally.This report on shoreline change on three of the eight main Hawaii islands (Kauai, Oahu, and Maui) is one in a series of reports on shoreline change in coastal regions of the United States that currently include California, the Gulf of Mexico region, the Southeast Atlantic Coast, and the Northeast Atlantic Coast. The report summarizes the methods of analysis, documents and interprets the results, explains historical trends and rates of change, and describes the response of various communities to coastal erosion. Shoreline change in Hawaii was evaluated by comparing historical shorelines derived from topographic surveys and processed vertical aerial photography over time. The historical shorelines generally represent the past century (early 1900s-2000s). Linear regression was used to calculate rates of change with the single-transect method: long-term rates were calculated from all shorelines (from the early 1900s to the most recent), whereas short-term rates were calculated from post-World War II shorelines only.Beach erosion is the dominant trend of shoreline change in Hawaii. However, shoreline change is highly variable along Hawaii beaches with cells of erosion and accretion typically separated by only a few hundred meters on continuous beaches or by short headlands that divide the coast into many small embayments. The beaches of Kauai, Oahu, and Maui are eroding at an average long-term rate for all transects (shoreline measurement locations) of -0.11 ± 0.01 m/yr (meters per year) and an average s...

Coastline evolution of Portuguese low-lying sandy coast in the last 50 years: an integrated approach

“…Measurement uncertainties include errors related to coastline digitization (E d ) (Fletcher et al, 2003), image resolution (E ir ) (Coyne et al, 1999;Catalão et al, 2002) and image rectification (E r ) (Shoshany et al, 1996;Fletcher et al, 2003).…”

“…Flowchart procedures for using aerial photographs to extract coastline indicators. Fletcher et al (2003) state another physical component of error, representing short-term variability in coastline position. In this study, these sources of error were eliminated by adopting the foredune shoreward edge approach, in accordance with other works (e.g.…”

“…According to Fletcher et al (2003) these errors are random and uncorrelated and can be represented by a single measure (U p ) calculated as the square root of the sum of the squares (Coyne et al, 1999;Fletcher et al, 2003):…”

“…This encouraged the development of numerous long-term (> 30 years according to Fletcher et al, 2012) studies worldwide which, in most cases, lack the broader scale perspective, instead evaluating change at micro/meso spatial scales and generally focusing only on known problematic areas.…”

“…The United States launched the National Assessment of Coastline Change Project, which delivered a number of reports organized by coastal regions (e.g. Fletcher et al, 2012). The European counterpart is the EUROSION project framework (European Commission, 2004), which conducted a country-by-country evaluation of coastal erosion at the European scale and delivered three main final products: (1) online reports, including major findings and recommendations; (2) a GIS database, which includes Europe's coastline vectors at 1 : 100 000 scale; and (3) a coastline management guide.…”