A landslide is a rapid movement of earth materials down-slope under the force of gravity. Landslides can cause slumpage or subsidence, damage to homes, roads and property, and possible damage to utilities such as water and sewer mains in urban areas. Different types of possible landslides include:
Coastal Landslides: Triggered by chronic bluff erosion in areas with mud banks that are over 20 feet high as a result of the internal instability of sediment bluffs and their potential to rapidly move large amounts of land down-slope under the influence of gravity.
Inland Landslides: Occur in almost any area of the State based on geological and topographic/geomorphic factors.
Most landslides have occurred in glacial-marine clay deposits in the valleys and lowlands of southern Maine. Small and slower moving slides are common along steep valley sides and shorelines where there are clay deposits. However, large destructive slides are rare, the most recent occurring in April of 1996 when a steep bluff along the north shore of Rockland Harbor slumped toward the ocean.
Maine’s experience with landslides, alongside the continual rise in the level of the sea, indicates that there is a high probability that landslides will continue to occur on an annual basis in various locations along the Maine coast. Maine does face several challenges in term of dealing and preparing for landslides:
Maine’s commitment to coastal geology is small.
No user-friendly program for mitigating landslides exists.
There is limited insurance for geological risks.
Increasing mitigation is needed.
Marine geologists of the Maine Geological Survey map and study areas that may be more susceptible to various types of bluff erosion. Their materials are available to city and regional planners. Careful planning and zoning are encouraged. Retaining open spaces in vulnerable areas not only enhances the worth of the surrounding area, but may prevent future destruction.
* An occurrence of this hazard could possibly be initiated by a deliberate act.