ABSTRACT

Romine, B.M. and Fletcher, C.H., 2013. A summary of historical shoreline changes on beaches of Kauai, Oahu, and Maui, Hawaii.

Shoreline change was measured along the beaches of Kauai, Oahu, and Maui (Hawaii) using historical shorelines digitized from aerial photographs and survey charts for the U.S. Geological Survey's National Assessment of Shoreline Change. To our knowledge, this is the most comprehensive report on shoreline change throughout Hawaii and supplements the limited data on beach changes in carbonate reef–dominated systems. Trends in long-term (early 1900s–present) and short-term (mid-1940s–present) shoreline change were calculated at regular intervals (20 m) along the shore using weighted linear regression. Erosion dominated the shoreline change in Hawaii, with 70% of beaches being erosional (long-term), including 9% (21 km) that was completely lost to erosion (e.g., seawalls), and an average shoreline change rate of −0.11 ± 0.01 m/y. Short-term results were somewhat less erosional (63% erosional, average change rate of −0.06 ± 0.01 m/y). Maui, Hawaii, beaches were the most erosional of the three islands with 85% of the beaches erosional, including 11% lost, and an average change rate of −0.17 ± 0.01 m/y. Seventy-one percent of Kauai, Hawaii, beaches were erosional, including 8% lost, with an average change rate of −0.11 ± 0.01 m/y. Most (60%) of the Oahu, Hawaii, beaches were erosional, including 8% lost, with an average change rate of −0.06 ± 0.01 m/y. Short-term results for Maui, Hawaii, and Oahu, Hawaii, were roughly the same as those found in the long term. Short-term analysis for Kauai, Hawaii, was less conclusive with an accretional average rate, but most of the beaches were erosional. Spatially, shoreline change is highly variable along the Hawaii beaches (length scales of hundreds of meters). Areas of chronic erosion were identified on all sides of the islands.

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