Causes and Mitigation Strategies of Landslides in New Zealand
The cause of Landslides can be due to many different reasons. Firstly the pull of gravity on a slope is significant but several reasons can increase the risk of a landslide. Many countries experience landslides because of these reasons but amongst them New Zealand has a high number. The mountain ranges in New Zealand are still being uplifted. Rocks are often weakened by folding and faulting, and there is also continual earthquake activity. The most common landslides in New Zealand are shallow and fast. They flow down like ‘wet cement’. Landslides are a crucial problem in the life of the people of New Zealand but mitigation strategies are being enforced to help cut down the damage they cause.
All types of landslides occur in New Zealand. They are classified by there material and there movement. They can displace whole mountain sides, taking millions of cubic metres of material, at up to 200 kilometres per hour. The opposite of these are slow moving; only shifting a few centimetres a year. Landslides can produce a lot of river sediment. Most of the entering the rivers in New Zealand are caused by landslides. In March 1988, Cyclone Bola hit the East Coast. The landslides that started because of this produced over 20 million tonnes (64%) of the sediment of the Waipāoa River. However in the long term only 10-20% of the sediment in rivers in New Zealand is caused by landslides.
Green lake
The largest landslide ever recorded in New Zealand 13,000 years ago in Fiordland. Around 27 cubic kilometres of material collapsed in a hard rock landslide that covered an area of over 45 square kilometres. A whole chunk of the mountain range collapsed into the valley. Some depressions in the surface filled with water, forming sizable holes such as Green Lake, rather than the usual ponds.
New Zealand is a multiple hazard hotspot. Many of these make it a hotspot for landslides. Firstly the unstable slopes around the country already have bad pre-conditions that contribute.
All types of landslides occur in New Zealand. They are classified by there material and there movement. They can displace whole mountain sides, taking millions of cubic metres of material, at up to 200 kilometres per hour. The opposite of these are slow moving; only shifting a few centimetres a year. Landslides can produce a lot of river sediment. Most of the entering the rivers in New Zealand are caused by landslides. In March 1988, Cyclone Bola hit the East Coast. The landslides that started because of this produced over 20 million tonnes (64%) of the sediment of the Waipāoa River. However in the long term only 10-20% of the sediment in rivers in New Zealand is caused by landslides.
Green lake
The largest landslide ever recorded in New Zealand 13,000 years ago in Fiordland. Around 27 cubic kilometres of material collapsed in a hard rock landslide that covered an area of over 45 square kilometres. A whole chunk of the mountain range collapsed into the valley. Some depressions in the surface filled with water, forming sizable holes such as Green Lake, rather than the usual ponds.
New Zealand is a multiple hazard hotspot. Many of these make it a hotspot for landslides. Firstly the unstable slopes around the country already have bad pre-conditions that contribute.