What month do most landslides occur in Seattle?

Seattle’s geology and climate contribute to landslides Average annual rainfall is about 37 inches and most landslides occur during the rainy season, which begins approximately in October or November and lasts through the following April or May. In general, landslides are common on coastal bluffs and other steep slopes.

Why is Mt meager especially prone to landslides?

It enters Meager Creek at a right angle which promotes deposition and blockage as opposed to downstream transportation. This means that Meager Creek is very susceptible to creating landslide dams (Bovis & Jakob, 2000).

Why does Seattle have landslides?

The most frequent triggers of landslides in Seattle are human alteration of the slope, groundwater saturation, or a combination of both. For example, a person may cause a pipe to leak and saturate the ground, triggering a landslide. Landslides that occur under water are called submarine landslides. debris flow.

Which two Canadian provinces have the highest landslide risk?

Based on this criterion, landslides are the most destructive geological hazard in Canada. Landslide damage, measured by landslide fatalities, is heavily concentrated in two regions; the St. Lawrence Lowlands of Québec and the Canadian Cordillera south of 55°N in the provinces of British Columbia and Alberta.

Are landslides common in Seattle?

Seattle has steep hills, wet winters, and geology that is prone to landslides. Landslides occur frequently, especially in the winter and early spring. 8.4% of the city’s surface is covered by areas identified as slide prone in the city’s Environmentally Critical Areas Ordinance.

How was the Lawton clay deposited?

As it entered the northern part of the Puget Sound basin, the advancing Vashon glacier probably dammed the drainage of the rivers whose sediments are seen in the Olympia Interbeds. The dammed rivers formed a series of large lakes. The Lawton Clay accumulated at the bottom of these large lakes.

What is a landslide hazard map?

These maps might be as simple as a map that uses the locations of old landslides to indicate potential instability, or as complex as a map incorporating probabilities based on variables such as rainfall, slope angle, soil type, and levels of earthquake shaking. …

Where in Canada are landslides most likely to occur?

Large landslides only occur approximately every 10 years in Canada. They occur across all regions, but the most destructive landslides happen in the mountain ranges of British Columbia and Alberta, as well as some parts of Quebec and Ontario.

Which broad region of Canada has the greatest landslide hazards?

“This unstable soil is the most common cause of landslides in the St. Lawrence Valley, Ottawa to Quebec City, and as far as the Saguenay region.” British Columbia fatalities due to landslides total 356, followed by Quebec at 239. Newfoundland is third at 103 fatalities.

Where were most of the landslides in 1996?

Landslides were most abundant along the bluffs of Puget Sound, Lake Washington, Lake Union, and Portage Bay. West Seattle and Magnolia Bluff had many damaging landslides, while few landslides occurred along the 1-5 corridor. Many small landslides were scattered west and south of Seattle in Kitsap and Pierce counties.

What is Esperance sand?

The Esperance Sand and the Lawton Clay are part of a sequence of Pleistocene glacial deposits in the Puget Sound Basin. Deposits in this sequence are often overconsolidated, have a wide range of hydraulic conductivities, are laterally hetero- geneous, and form steep, landslide-prone coastal bluffs.