Important information for visitors to Milford Sound.
Those planning to visit Milford Sound sould be aware that this region is susceptible to various natural hazards and risks, detailed below. While New Zealand’s stunning landscapes make it a premier travel destination they also come with inherent hazards – and Piopiotahi Milford Sound is no exception.
Earthquake
The Alpine Fault stretches approximately 800 kilometers along the spine of New Zealand’s South Island and stands as one of the world’s significant geological landmarks. This fault is responsible for the striking geological formations visible in Milford Sound. It remains active, with rupture events occurring approximately every 300 years, the most recent significant earthquake taking place in 1717 AD. For further details, please visit the AF8 website.
Analysis suggests that major ruptures could exceed a Magnitude of 8, indicating that the next event along the Alpine Fault may be extremely destructive. Such an occurrence could also trigger landslides and potentially lead to a localized tsunami. A rupture of Magnitude 8 is expected to severely impact critical infrastructure in Milford Sound, including essential road networks.
What to do in an earthquake.
- DROP, COVER and HOLD. Drop down to your hands and knees. Cover your head and neck.
- If the earthquake is LONG or STRONG, GET GONE. Move immediately to the nearest high ground or as far inland as possible. Do not wait for an official tsunami warning.
Tsunami
Milford Sound is vulnerable to both locally generated and distant tsunami events. Scientific studies suggest that a severe earthquake (Magnitude 8 or greater) could trigger a destructive tsunami caused by landslides, including undersea ones. Further analysis indicates that the considerable volume of water displaced by such a landslide might lead to a tsunami with significantly high waves and run-up.
Given that Milford Sound attracts numerous visitors daily, a landslide-induced tsunami of any noteworthy height would present a serious threat to those present. The only warning for these individuals would be the occurrence of an earthquake. MSTL is currently pursuing a risk assessment concerning landslide-induced tsunamis. This notice will be updated once the risk assessment has been completed and reviewed.
Severe Weather Events
Flooding
Milford Sound’s rugged landscape leads to substantial yearly rainfall, averaging over 7 meters annually. Due to low soil absorption, rain often flows directly into the sea, lakes, or high-capacity rivers in the region. It is not uncommon for rainfall to reach accumulations of 200 mm within 24 hours, with intensities soaring to 30 mm per hour.
While the road infrastructure is well-equipped to handle most heavy rain events, prolonged and intense rainfall can potentially close roads and isolate Milford Sound until repairs are completed.
Landslides
Landslides frequently occur in Milford Sound as a result of consistent severe weather and the area’s soil conditions. Near the coast, landslides are mainly driven by vegetation, where topsoil is scarce. However, as you move further inland, the composition consists of a greater amount of rock and soil.
Snow and Avalanches
Avalanches can present a hazard in the Milford Sound region, particularly impacting the road networks that serve the area. Although the Milford Road Alliance takes preventative measures—such as avalanche control—to greatly reduce this risk, avalanches still happen occasionally.
To ensure a safe experience, it’s essential to:
- Stay updated on weather conditions.
- Follow travel advisories.
- Be prepared for sudden changes.
Fiordland is New Zealand’s largest and most isolated national park, it can experience sunshine, snow, wind, and rain all within a single day, no matter the season.