70 percent of beaches eroding on Hawaiian islands Kauai, Oahu, and Maui

70 percent of beaches eroding on Hawaiian islands Kauai, Oahu, and Maui

An assessment of coastal change over the past century has found 70 percent of beaches on the islands of Kaua'i, O'ahu, and Maui are undergoing long-term erosion, according to a U.S. Geological Survey (USGS) and University of Hawai'i (UH) report. Scientists from the USGS and the School of Ocean and Earth Science and Technology (SOEST) at UH studied more than 150 miles of island coastline (essentially every beach) and found the average rate of coastal change - taking into account beaches that are both eroding and accreting - was 0.4 feet of erosion per year from the early 1900s to 2000s. Of those beaches eroding, the most extreme case was nearly 6 feet per year near Kualoa Point, East O'ahu.

"The inevitable fate of the Hawaiian Islands millions of years into the future is seen to the northwest in the spires of French Frigate Shoals and the remnants of other once mighty islands, ancestors of today's Hawaii, but now sunken beneath the sea through the forces of waves, rivers, and the slow subsidence of the seafloor," explained USGS Director Marcia McNutt.

Of the three islands, Maui beaches experienced the highest rates and greatest extent of beach erosion with 85% of beaches eroding. Erosion is the dominant trend of coastal change on all three islands with 71% of beaches eroding on Kaua'i and 60% of beaches eroding on O'ahu. More than 13 miles of beaches in the study were completely lost to erosion - nearly all previously in front of seawalls. Sediment availability and transport are important factors in shoreline change, and human interference in natural processes appears to have impacted the measured rates of change.



The researchers found that, although Hawai'i beaches are dominated by erosion as a whole, coastal change is highly variable along the shore - with 'cells' of erosion and accretion typically separated by 100s of feet on continuous beaches or by rocky headlands that divide the coast into many small embayments. Most Hawaii beaches are composed of a mix of sediment derived from adjacent reefs and from the volcanic rock of the islands. The researchers used historical data sources such as maps and aerial photographs to measure shoreline change at more than 12,000 locations. Shoreline changes are measured in specialized Geographic Information System (GIS) software. This analysis of past and present trends of shoreline movement is designed to allow for future repeatable analyses of shoreline movement, coastal erosion, and land loss.

The report, titled "National Assessment of Shoreline Change: Historical Shoreline Change in the Hawaiian Islands," is the sixth report produced as part of the USGS's National Assessment of Shoreline Change project, which already includes the U.S. Gulf of Mexico and Atlantic coasts, as well as California. An accompanying report that provides the GIS data used to conduct the Hawaii coastal change analysis is being released simultaneously. (TerraDaily)

Hawaii Coastal Erosion Website


 

Featured image: The shoreline along Makapuu Point, Oahu, Hawaii (Credit: Brad Romine, University of Hawaii Sea Grant/ Hawaii Department of Land and Natural Resources)

Register/become a supporter

Support us AD-FREE

Your support is crucial for our survival. It makes this project fully self-sustainable and keeps us independent and focused on the content we love to create and share. 

Monthly subscription

Subscription options

Yearly subscription

Subscription options

You'll receive your ad-free account for 20x faster browsing experience, clean interface without any distractions, ability to post comments without prior editorial check, all our desktop and mobile applications (current and upcoming) ad-free and with the full set of features available, a direct line of communication and much more. See all options.

Tags: hawaii

Comments

No comments yet. Why don't you post the first comment?

Post a comment

Your name: *

Your email address: *

Comment text: *

The image that appears on your comment is your Gravatar