SAVE KIHEI

Groundwater Over-Extraction and Subsidence Hazards in Kihei

Groundwater Over-Extraction and Subsidence Hazards in Kihei, Maui, Hawaii

Abstract

Kihei, a coastal town on the island of Maui, faces significant challenges due to groundwater over-extraction. As water is drawn from the water table, the land gradually sinks—a phenomenon known as subsidence. This article examines the causes, consequences, and potential solutions for this pressing issue. We draw upon scientific studies and observations to highlight the risks posed by subsidence and its impact on infrastructure, coastal communities, and natural ecosystems.

1. Introduction

Kihei, situated along Maui’s southwestern coast, relies heavily on groundwater for agriculture, tourism, and residential use. However, unregulated extraction has led to adverse effects, including subsidence. Here, we explore the mechanisms behind subsidence and its implications.

2. Groundwater-Related Subsidence

Groundwater-related subsidence occurs when excessive pumping lowers the water table, causing the ground to sink. As sea levels rise, so does the water table, exacerbating the problem. In Kihei, this phenomenon threatens both natural and built environments.

3. Impact on Infrastructure

  • Roadways: Low-lying areas experience sinking, affecting roads and highways. Elevated or realigned roadways become necessary as subsidence progresses.
  • Wastewater Treatment Plants: Facilities like the Kahului wastewater treatment plant face increased vulnerability due to subsidence.
  • Developed Coastlines: Long swaths of developed coastline are at risk, impacting properties and infrastructure.

4. Coastal Vulnerability

Kihei’s coastal areas are particularly susceptible to subsidence:

  • Beach Erosion: About 85% of Maui’s shorelines battle persistent erosion. Subsidence exacerbates this problem, threatening beachfront properties.
  • King Tides and Wave Flooding: As sea levels rise, low-lying areas flood during king tides and storm events.

5. Long-Term Outlook

  • By 2030, sea levels are expected to rise 3 to 8 inches, with a 10% chance of 6 feet by 2100.
  • The current trajectory suggests 3 feet of sea level rise by the end of this century, potentially reaching 4 to 5 feet.

6. Mitigation Strategies

  • Regulation: Implement strict regulations on groundwater extraction to prevent further subsidence.
  • Infrastructure Adaptation: Elevate critical infrastructure and roads to withstand rising seas.
  • Community Awareness: Educate residents and policymakers about the risks and encourage sustainable water use.

Conclusion

Addressing groundwater over-extraction and subsidence in Kihei requires collaborative efforts. By understanding the science behind these processes and acting proactively, we can safeguard our coastal communities and preserve Maui’s natural beauty.

References

  1. Fletcher, C. H. (2020). Rising seas impacting shores – and it will only get worse. Maui News
  2. U.S. Geological Survey. (2023). Ground fractures and subsidence hazards, Island of Hawai‘i
ICYMI, more buildings in Kihei are sinking into the ground. Many areas in the Kihei floodplain are former or functional wetlands that previously had saturated soils for millennia, however, stress on the aquifer from over-extraction of groundwater, plus increased runoff from development which reduces aquifer recharge, are causing subsidence issues in many areas. One example is the Island Surf Building in Kihei which is currently undergoing emergency stabilization to reduce sinking.