Assessing Vulnerabilities to Sea Level Rise in Hawaiʻi County

By: Devon Aguiar & Rufus Lakjit

What is Sea Level Rise (SLR)?• SLR has been attributed to the melting of ice sheets and the thermal

expansion of warm seawater (Alley et al., 2005; Williams 2013).

Williams (2013), adapted from Rekacewicz (2005)

http://www.wired.co.uk/news/

www.wired.co.uk

• Predicted 1 ft. rise in global sea levels by mid century (2050) and 2.5-6.2 ft. rise by end of the century (2100).

• The rate of sea-level rise in Hawaii is approximately 1.5 mm/ year (Fletcher et al., 2012).

IPCC (2007) in Williams (2013)

• Assist County Planning Department in identifying priority planning areas.– Shoreline setback areas.

Objectives

Source: John P. Lockwood

• Identify Special Management Areas (SMA): “Therefore, special controls on development within the area alongthe shoreline are necessary to avoid permanent loss of valuable resources and the foreclosure of management options, and to insure that adequate public access is provided to public-owned or used beaches, recreation areas, and natural reserves, by dedication or other means” (COH Planning Commission, Rule 9-2).

Objectives

• Identify cultural/natural resources at risk.• Recreation areas.• Culturally significant areas.

Objectives

http://www.ksbe.edu/

Shoreline Hazards on Hawaiʻi Island

Subsidence: Sinking of the Earth’s surface in response to geologic or man-induced causes.

hvo.wr.usgs.gov

Erosion: Rates can range from 0.5-1 ft/yr (Fletcher et al., 2002)

Waves: Damage to property and endanger human life

Storms: Over wash from high waves and damage from strong winds

KITV News

Sea Level Rise: 1.5 in/decade for Hawaiʻi Island (Fletcher et al., 2002)

Methods• Gather and analyze:

– Elevation data– Shoreline Hazard data– Cultural/Natural resource data

• Create inundation polygons and identify impacted land parcels & cultural/natural resources.

• Hazard ratings: Moderately high & High risk

Honoliʻi

Hilo Bayfront

Kapoho

Keaukaha

SLR Results

This is a “Bathtub” model

Honoliʻi Kapoho

Bayfront & Keaukaha

1 ft. of SLR

3 ft. of SLR

6 ft. of SLR

Storm Hazard

High

Moderately High

Honoliʻi Kapoho

Bayfront & Keaukaha

Honoliʻi Kapoho

Bayfront & Keaukaha

Erosion Hazard Results

Moderately High

Moderately Low

Shoreline land parcels with < 20% slope (red) and >20% to <45% slope (yellow).

Use slope data we made or Compare to ours

Honoliʻi Kapoho

Bayfront & Keaukaha

Explain that county collected this data

Yes/no rated

Honoliʻi Kapoho

Bayfront & Keaukaha

Undergoing Subsidence

No Subsidence

Honoliʻi Kapoho

Bayfront & Keaukaha

Moderately high

Wave Hazard

Wave Hazard

High

North Kohala

Honoliʻi

Bayfront & Keaukaha

Kapoho

7 (Very High)

6 (High)

5 (Moderately High)

Overall Hazard

Wave Hazard Erosion Hazard Storm Hazard

High 140 land parcels 27 land parcels 2,071 land parcels

Moderately High 4,771 land parcels 672 land parcels 5,376 land parcels

Moderately Low 2,629 land parcels 6,816 land parcels 93 land parcels

Low 0 land parcels 25 land parcels 0 land parcels

Total amount of shoreline land parcels: 7,540

Results

Further Implications of Study

• Addition of tidal data in our study.• Use up to date elevation data (when it gets released…).• Connectivity between groundwater and SLR.

Mahalo!• Lisa Marrack, PhD. Candidate UC Berkeley• Ryan Perroy, UH Hilo Geography & Environmental Science Dept.• Chris, Nick, & Mark, UH Hilo SDAV• Chip Fletcher, UHBethany Morrison and Drew Marshall, County of Hawaiʻi

Planning Department Manoa SOEST• John P. Lockwood, Geohazards Consultants International Inc.