The Pacific Northwest’s endowment of natural beauty is the result of geologic processes. Volcanism, earthquakes and glaciation have formed our landscape.
One of the ubiquitous geologic processes of our landscape are landslides. They are an ongoing, continual natural phenomenon of our environment. Landslides will do what landslides have always done for eons. And since we have to coexist with landslides, it becomes imperative that we learn to live with landslides.
That responsibility lies not only in the hands of an individual, but it is also a collective, social responsibility.
Unfortunately, the need for proactive responsibility becomes evident only after a disaster or a tragedy strikes. Once that happens, we are reacting to the aftermath.
The March 22, 2014 tragedy at Oso, which took the lives of 43 people, is a case in point. While the geologists had already identified the landslide, we did not come to terms with the danger posed by the landslide until after the fact.
We must change that.
Our collective responsibility demands that we allocate necessary funding to carry out identification, characterization and risk evaluation of landslides in the state.
New technologies like lidar, in combination with geographic information system (or GIS), have dramatically improved the collection of geologic information. Lidar is a laser-based technology that allows a geologist to not only precisely and accurately locate landslides but also reveal its history and give clues to its makeup. It is analogous to observing a footprint on wet beach sand. By observing the footprint like a detective, we can learn a lot about the person who left that imprint on the beach sand. However, if grass grows over the footprint, it will shroud the details from our observation.
A geologist observing a bare bluff can read the history of how that bluff came in to existence. It is like reading a scroll of history. Similarly, the histories of landslides are imprinted on the ground. But vegetation and ground cover shroud fine details of the ground. Lidar technology, however lays the ground bare, allowing a geologist to not only see the landslide, but the clues that allow collection of a wealth of information.
Therefore, investing in lidar technology and GIS is a first step in addressing landslide risk. Legislation to enable the state Department of Natural Resources to expand its use of lidar mapping has been signed by the governor. The House budget proposal has included $4.6 million to fund the program. Money for the program was not specified in the Senate budget, but Senate leadership called the omission an oversight and funding will be included in the final budget approved by the Legislature.
Once the information is collected and analyzed, policy makers will have necessary information to fulfill their collective social responsibility. Individual responsibility begins with a fundamental recognition that geologic processes neither recognize property boundaries nor property rights.
Of all the factors that contribute to landslides, in over 84 percent of landslides, human factor appears to have played an important role.
A property owner on a hill slope or landslide area can potentially create a situation where the neighbor’s property can be affected. Therefore, owning a property on a slope or potential landslide area comes with an added responsibility and obligation.
That responsibility starts with keeping a vigilant eye over the slope. Any ground changes, such as cracks, are an important clue to impending earth movements. Vegetation on the slope provides anchoring to surface soils and absorbs water. Native vegetation comprising of trees, shrubs and groundcover are an important element on the slope.
Surface water and groundwater are of the utmost importance on the slope and landslide area. Keeping the surface water flowing over the slope and preventing erosion from flowing water can contribute to keeping the slope stable. Never build any permanent irrigation system on the slope.
Each landslide has its unique characteristics. They are based on local geology, topography, surface and groundwater regime, weathering processes, vegetation to name some important ones. Either required by jurisdiction or not, involving an engineering geologist, a canary of coal mine when it comes to slopes and landslide, can appraise a property owner of their situation. An engineering geologist with expertise in landslide is almost a necessity.
We live in a world where with a flip of a switch or a stroke of hand, we control our environment. That mindset of control pervades our sense of reality. We do not however, have that degree of control over geologic processes.
In confronting the risk posed by landslides, the best approach is to take individual and collective responsibility to prevent putting property and lives from coming in the harms way.
Moin Kadri is Washington state licensed engineering geologist.
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