Will global warming make concern about avalanches unnecessary?
Many expect that global warming will continue and that less snow will fall as a result. If this turns out to be true, will our days of worrying about avalanches be over?
No, says the Snow Avalanche and Landslide Research Center, whose research is focused on this very issue. The following provides a peek at the centers research.
Extreme heat followed by heavy snow
It is evident that the deepest snow amounts in snow regions are declining compared to 30 years ago. However, snows effect on society is not measured simply by depth; the way snow falls also has an impact. Some researchers point out that rising temperatures resulting from climate change significantly influence swings in climatic phenomena that can cause sudden heavy snowfall. They also suggest that early spring, a time when snow usually falls, will see more and more rain in the future.
Research on avalanches that may result from global warming
Since April of last year, research has been moving forward based on the following perspectives: If global warming continues at its current pace, the time when early spring snow changes to rain will occur earlier. If rain falls while large amounts of snow remain on mountain slopes, will the characteristics of avalanches change? And, if avalanche characteristics change, will conventional experience alone be sufficient in preparing for disasters?
The research described above is a joint effort among three organizations: the Snow Avalanche and Landslide Research Center (Myoko City, Niigata Prefecture) and Snow and Ice Research Team (Sapporo City, Hokkaido) of PWRI, and the Shinjo Branch of the Snow and Ice Research Center, National Research Institute for Earth Science and Disaster Prevention (Shinjo City, Yamagata Prefecture). During the current fiscal year, these organizations will be gathering data through laboratory experiments and other activities.
The Snow and Ice Research Center possesses one of the largest snow laboratories in the world. It also has the only equipment capable of making artificial snow with crystalline forms resembling natural snow available anywhere. The experiments being conducted for the research begin by artificially causing rain to soak into snow at an air temperature of around 0 degrees Celsius. Then, as the rain soaks in, they seek to find connections between snow density and snow strength based on air temperature measurements. The ultimate aim is to understand avalanche conditions in environments that are warmer than those seen today.
(Contact: Snow Avalanche and Landslide Research Center)
Research on Geological Characteristics that Cause Tunnel Deformation after
Completion, and Measures against such Deformation
- To Ensure Safe and Reliable Tunnels -
Rapidly deteriorating rocks affected by changes in underground stress conditions and groundwater distribution caused by civil engineering work, including cut earth and excavation, are widely distributed throughout the Hokkaido and Tohoku regions.
Tunnels constructed in such locations may have deformations, including cracked walls or heaving road surfaces (see the figure on top right) after a few months or several years, even if there were no problems at the time of construction. In severe cases it is not possible to pass through these tunnels safely. When these phenomena occur, it costs a tremendous amount of money to repair and implement measures, and the tunnel must be closed, causing inconvenience to local traffic as well as seriously affecting the local communities/society and the economy.
In order to avoid these phenomena in actual tunnel construction, problematic rocks are tested for engineering properties (slake test, middle photo on the right) and deterioration analysis is conducted to investigate the status of clay minerals. Various measures have also been taken for the construction of tunnels, including the use of stronger structures. However, regardless of these efforts with regard to investigation and implementation of measures, it is still difficult to entirely prevent tunnel deformation caused by rock properties, after completion.
With the aim of eliminating the risk of tunnel deformations after completion, the Geological Hazards Research Team of CERI analyzes cases of tunnel deformation and investigates rocks collected from heaving sections after a few years of tunnel service, by means of boring surveys (a method of drilling the ground and investigating actual rocks). The team has confirmed that there are cases in which similar-looking extremely deteriorated and unaffected rocks are mixed (bottom right-hand photo on previous page).
It is considered that this phenomenon is caused by complicated relations of different factors, including the release of stress accumulated in the ground (stress relief) and a condition in which clay minerals with expanding properties are originally contained in rocks, accelerating deterioration as the clay materials come into contact with water and air (slaking).
In the future, we hope to continue research into methods to find rocks that deteriorate over medium- to long-term periods, and techniques to construct tunnels in such conditions.
(Contact: Geological Hazards Research Team, CERI)
How does sand augmentation affect benthic algae growing in riverbeds?
|There is little sand below the dam|
|Earth-and-sand supply experiment|
In areas immediately downstream of dams, a phenomenon known as armor coat can occur whereby sand and small gravel disappear from the riverbed as sediment supply declines, leaving the riverbed surface covered with stones and boulders. This change in the substrate materials is known to have various impacts in aquatic organisms. The artificial supply of sand and small gravels by sediment bypass and sand augmentation (sand brought from another place) is receiving attention as a method for improving downstream environments. However, if artificial supply is conducted in an area below a dam with timing that differs from natural flooding, the sediment supplied can become deposited on the riverbed. Such a situation can also affect aquatic organisms.
The Aqua Restoration Research Center (ARRC) is working to clarify the effects that the supply or non-supply of sand has on aquatic organisms. Its approach here involves replacing the bed surfaces of two experimental streams with large stones and supplying only one of the streams with sand. The objective is to elucidate the effect that supply of sand has on aquatic organisms that inhabit on riverbeds. Experiments conducted in the summer of last year demonstrated how the primary production of benthic algae changes depending on whether or not sand is supplied as well as on the amount of sand that is supplied. The experiments showed that benthic algae had clearly lower primary productivity when sand was supplied than when it was not. Moreover, the experiments showed that supply of sand has the effect of controlling growth of benthic algae.
Looking forward, ARRC intends to create a biomass model for benthic algae that takes sand supply into account based on the results of these experiments. It also plans to develop the model into a tool for quantitative evaluation of the impact of sediment supply. It should be noted that the schedule of experiments planned for next fiscal year and beyond, as well as other relevant information, is continually being posted on the ARRC website. This information is available to all who are interested.
(Contact: Aqua Restoration Research Center)