Overview
Aloha and welcome to the Hawaiʻi Shoreline Study web map! While sandy beaches are a recreational destination for both residents and visitors, they also serve many important cultural and ecological functions. As a buffer between the land and sea, they are highly variable environments, and thus vulnerable to sea-level rise, erosion, and other hazards. Because much of the shoreline is developed, communities around the state are faced with the challenge of how to deal with these hazards, both now and in the future. To assist in decision-making, the Coastal Geology Group, through government-partnerships, provides shoreline change data to the public. We currently have data for Kauaʻi, Oʻahu, and Maui; however, we hope to include the other main Hawaiian islands soon. The products on this web map are frequently updated.
Directions: This viewer was created to visualize and share data from the Hawaiʻi Shoreline Study. For general navigation tips of this web map, please visit this ArcGIS Online tutorial. In the web map, more information is available in each layer’s pop-up window. To view this information, zoom to an area and click on the layer of interest. A pop-up window with more specific information for that layer will appear. General descriptions of the layers are below, along with links to download them at the state or island extent.
Mosaics: Individual mosaics can be downloaded from a pop-up window. Click on the Footprint of interest and the available mosaics for that area will be displayed in the pop-up window. Scroll through the pop-up window to see the different mosaics by clicking the right-pointing arrow in the top right corner of the pop-up window. NOTE: Files cannot be downloaded through Chrome. Please use an alternative browser. Mahalo.
For further inquiries and assistance, please contact Aloha Kapono at tkapono@hawaii.edu.
Credits: Mahalo to the multiple organizations and agencies that have supported and continue to support this project.
Suggested Citation: Coastal Geology Group in the School of Ocean and Earth Science and Technology (SOEST) at the University of Hawaiʻi. 2021. Hawaiʻi Shoreline Study. Retrieved from https://www.soest.hawaii.edu/crc/index.php/hawaii-shoreline-study-web-map
⚠ Disclaimer: The data and maps in this tool illustrate the scale of potential land loss and shoreline movement, not the exact location of future shorelines. Future projections do not account for artificial shoreline hardening, future construction, and/or other change(s) in circumstance including, but not limited to, government regulations and/or acts of God. These projections are based on specific assumptions about the magnitude and timing of future sea level rise from the IPCC (2013) which may not reflect actual future conditions. The data, maps, and information provided in this viewer are intended to improve sea level rise awareness and preparedness, and do not guarantee the safety of an individual, property, and/or structure. The contributors and sponsors of this product do not assume liability for any injury, death, property damage, and/or other effect(s) of sea level rise. This map should not be used for navigation or precise spatial analysis. The user of these products assumes any and all risk associated with said use and/or with the results, performance, implementation, and or analysis of the data there from.
The data used for this tool will be periodically updated and the Coastal Geology Group is currently working to publish a separate user guide that will document all methodologies, data, and/or assumptions that were used in creating this tool. For additional information please see Anderson et al. (2018).
Description of Files
Low Water Mark
The instantaneous Low Water Mark (LWM), or toe of the beach, is visually interpreted and digitized from the corresponding historical orthophoto mosaic. It is used as a proxy of the seaward, or makai, extent of beach area in beach width calculations in the historical shoreline change analysis of the island.
Download shapefile:
NOTE: Files cannot be downloaded through Chrome. Please use an alternative browser. Mahalo.
Vegetation Line
The Vegetation Line or ‘veg line’ of the beach is visually interpreted and digitized from the corresponding historical orthophoto mosaic. The veg line characterizes the annually stable seaward extent of vegetation. It is used as the landward or mauka extent of beach area in beach width calculations in the historical shoreline change analysis of the island.
Download shapefile:
NOTE: Files cannot be downloaded through Chrome. Please use an alternative browser. Mahalo.
Historical Shoreline Transects
Shoreline transects represent measurement locations for historical shoreline change analysis. Transects are cast shore-normal from an offshore baseline drawn to represent the approximate shape of the shoreline through time. The nominal distance between transects is 20 meters as measured along the baseline. In the attribute table, each transect contains: the smoothed shoreline change rate, the smoothed uncertainty calculated for that rate, the smoothed standard deviation of the rate, the number of shorelines used to calculate the rate, and the degrees of freedom.
Download shapefile (feet):
Download shapefile (meters):
NOTE: Files cannot be downloaded through Chrome. Please use an alternative browser. Mahalo.
Future Shoreline Transects
The projected shoreline change rate for the specified year is the projected long-term trend in beach variability under future sea-level rise conditions for that time. Sea-level rise is expected to accelerate in the future, leading increased rates of shoreline recession along already retreating shorelines and decreased rates and/or reversal of currently advancing shorelines. Model projections are calculated following the shoreline change model described in Anderson et al. (2015). Mid-range projections represent outcomes that are more likely to occur. However, more conservative projections may be better to consider for effective planning. Thus, three different projections are provided.
Download shapefile (feet):
Download shapefile (meters):
NOTE: Files cannot be downloaded through Chrome. Please use an alternative browser. Mahalo.
Future Erosion Hazard Zones
The erosion hazard zone is a spatial depiction of lands that are projected to be vulnerable to erosion by the specified year. The hazard zone is not meant to be a prediction of the exact lands that will be eroded in the future, nor a prediction of where the shoreline will be in the future. Rather, the erosion hazard zone represents lands that fall within a zone with a certain likelihood of exposure to erosion, according to probabilistic modeling.
Future coastal change is projected following Anderson et al. (2015), in which historical shoreline trends are combined with projected rates of sea level rise (IPCC RCP 8.5). At each transect location (spaced 20 m apart), the 80th percentile of the projected vegetation line (higher percentiles are more landward) is used as the inland extent of the projected erosion hazard zone for the specified year. This inland extent is connected with the coastline (zero-elevation contour, mean sea level) to create polygons depicting erosion hazard zones.
The projected shoreline change rate is the estimated long-term trend for the shoreline that is likely located somewhere within the hazard zone (unless the shoreline has high rates of historical advance). The exact location of a future shoreline, however, is not shown within an erosion hazard zone.
Download shapefile (0.5 ft, 2030):
Download shapefile (1.1 ft, 2050):
Download shapefile (2.0 ft, 2075):
Download shapefile (3.2 ft, 2100):
NOTE: Files cannot be downloaded through Chrome. Please use an alternative browser. Mahalo.
Last updated: March 2021