That's because both are considered a form of "earth movement", and like an earthquake or sinkhole, they're generally excluded from a standard homeowners insurance policy. Flood policies often don't cover damage from landslides or mudslides, either.
How can we prevent mudslides? Planting and water diversion are the best methods to help prevent mudslides. Appropriate planting is a good way to protect a hillside, but allow time for roots to reach the most beneficial depth.
Where do mudslides mostly occur? Mudslides typically occur in areas with steep hillsides, gullies and other narrow channels that make it easy for rain, mud and debris to flow through -- much like the terrain in Southern California, Peterson said.
These gullies and other passageways form over millions of years. How do you survive a mudslide? Method 1 Evacuating Safely Monitor the news and evacuate when recommended. Drive away from the mudslide if you have time. Run sideways away from the mudslide if you're outside. Follow your family's emergency plan if you have one. Stay away until the threat of mudslides has passed if you've evacuated. What season do mudslides occur? Gravity acts as landslide's best friend and forces things downhill.
Additionally, drought conditions may lead to soil compaction, and severe wildfire events may leave slopes denuded and hydrophobic. Rockfalls are often caused by erosion of earth around larger rocks that then become loose and fall. Earthquakes can also lead to landslides and rockfalls. Nearly all geologic and soil hazards are highly localized events. In fact, much of what helps determine the level of hazard risk at a precise location are the features and process that lie underground.
These variables make the identification, assessment, and mapping of geologic and soil hazards more difficult, especially for the purpose of designing and implementing planning tools or strategies. In recognition of this fact, the Colorado Geological Survey CGS provides a range of services and resources to assist and advise local planners on geologic hazards, including the review of preliminary plans or reports for new development as well as conducting studies, collecting geologic information, and publishing maps, reports, and bulletins with regard to land use activities.
Still, while a variety of relevant national and statewide data exists to determine hazard risk in a very general sense including geologic, topographic, and soil maps , most Colorado communities do not have readily accessible information or detailed maps necessary for implementing local regulations.
Doing so often requires field surveys and even geotechnical tests by trained earth scientists to identify specific problems associated with land development and public safety. Consultation with geologists and other experts familiar with local conditions is an important first step for local planners seeking to assess the risk of their community and specific areas that are susceptible to geologic and soil hazards.
The CGS and other official sources can provide map information on levels of risk, past hazard events, and the probability of future events. More site-specific data and mapping, however, will need to be obtained through technical studies for specific areas of concern. Communities may opt to hire a consulting geologist or geotechnical engineer to perform this work, or require such expert studies as part of the local development permitting process.
As summarized in the chapter, Planning Framework , there are several state statutes and regulations that specify requirements for the submission of geologic suitability reports in conjunction with land use applications to be reviewed by CGS. At a minimum, planners should have a general understanding of where geologic and soil hazards exist and what their implications are for safe development so that the viability of available planning tools and strategies to reduce their risk can be further evaluated.
Ideally, using this information, most communities should be able to prepare a map of the entire community that distinguishes particular areas of concern. This effect can occur in the form of intense rainfall, snowmelt, changes in ground-water levels, and water-level changes along coastlines, earth dams, and the banks of lakes, reservoirs, canals, and rivers.
Landsliding and flooding are closely allied because both are related to precipitation, runoff, and the saturation of ground by water. In addition, debris flows and mudflows usually occur in small, steep stream channels and often are mistaken for floods; in fact, these two events often occur simultaneously in the same area. Landslides can cause flooding by forming landslide dams that block valleys and stream channels, allowing large amounts of water to back up.
This causes backwater flooding and, if the dam fails, subsequent downstream flooding. Also, solid landslide debris can "bulk" or add volume and density to otherwise normal streamflow or cause channel blockages and diversions creating flood conditions or localized erosion. Many mountainous areas that are vulnerable to landslides have also experienced at least moderate rates of earthquake occurrence in recorded times.
The occurrence of earthquakes in steep landslide-prone areas greatly increases the likelihood that landslides will occur, due to ground shaking alone or shaking-caused dilation of soil materials, which allows rapid infiltration of water.
The Great Alaska Earthquake caused widespread landsliding and other ground failure, which caused most of the monetary loss due to the earthquake. Other areas of the United States, such as California and the Puget Sound region in Washington, have experienced slides, lateral spreading, and other types of ground failure due to moderate to large earthquakes.
Widespread rockfalls also are caused by loosening of rocks as a result of ground shaking. Worldwide, landslides caused by earthquakes kill people and damage structures at higher rates than in the United States. Landslides due to volcanic activity are some of the most devastating types. Volcanic lava may melt snow at a rapid rate, causing a deluge of rock, soil, ash, and water that accelerates rapidly on the steep slopes of volcanoes, devastating anything in its path.
These volcanic debris flows also known as lahars reach great distances, once they leave the flanks of the volcano, and can damage structures in flat areas surrounding the volcanoes. The eruption of Mount St. Helens, in Washington triggered a massive landslide on the north flank of the volcano, the largest landslide in recorded times. Vulnerability to landslide hazards is a function of location, type of human activity, use, and frequency of landslide events.
The effects of landslides on people and structures can be lessened by total avoidance of landslide hazard areas or by restricting, prohibiting, or imposing conditions on hazard-zone activity. Local governments can reduce landslide effects through land-use policies and regulations. Individuals can reduce their exposure to hazards by educating themselves on the past hazard history of a site and by making inquiries to planning and engineering departments of local governments.
They can also obtain the professional services of an engineering geologist, a geotechnical engineer, or a civil engineer, who can properly evaluate the hazard potential of a site, built or unbuilt. The hazard from landslides can be reduced by avoiding construction on steep slopes and existing landslides, or by stabilizing the slopes.
Stability increases when ground water is prevented from rising in the landslide mass by 1 covering the landslide with an impermeable membrane, 2 directing surface water away from the landslide, 3 draining ground water away from the landslide, and 4 minimizing surface irrigation. The U. Geological Survey Landslide Program has information, publications, and educational information on its Web site.
For general information about slides, debris flows, rock falls, or other types of landslides in your area, contact your city or county geology or planning office. For an assessment of the landslide risk to an individual property or homesite, obtain the services of a State-licensed geotechnical engineer or engineering geologist. Often, personnel in State or county planning or engineering departments can refer competent geotechnical engineers or engineering geologists. Freezing and thawing contribute to soil creep by progressively moving soil particles down the hill.
Creep is manifested at the surface by such things as tilted utility poles that become more out of alignment every year. Vegetation helps reduce the rate of soil creep. Earth material that has moved as a unit along a curved surface is called slump. A slumped mass of sediment is typically clay rich.
Slump usually results when the geometrical stability of a slope is compromised by the undercutting of its base, such as by wave action, a meandering river, or construction. Previous MassWasting Controls.
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