How much effort should society spend in preparing for rare events? The answer surely depends on the scope of the event, its rarity, and damage or costs associated with preparations. So, with these criteria in mind let’s examine potential responses to the Lake Champlain flooding of 2011.

The question is relevant because an international workgroup has recently released a plan of study for how to address the floods, and tentatively recommended $14 million worth of studies that might lead to a proposed solution. The workgroup was assembled by and reports to the International Joint Commission (IJC). The IJC helps implement a 1909 treaty between Canada and the United States designed to prevent and resolve disputes over water resources between the two countries. The IJC was asked by the governments of Canada and the United States to figure out what studies might be necessary to remediate flood damage on Lake Champlain.

The workgroup has put together three options for studies. Option A, the most basic, would cost $5 million over three years. It would evaluate the causes and impacts of past floods including 2011, assess the possibilities offered by the best possible flood plain management practices, provide an indication of benefits associated with flood forecasting and real-time mapping, evaluate adaptation strategies for climate related changes in water supply, and develop a hydrologic model for the lake. Option B would cost almost $11 million over five years. It would include the Option A studies and add additional ones on wetlands and fauna, and more detailed investigations of mitigation measures, both structural and non-structural. It would also include a more thorough assessment of how wind and waves exacerbated flood damage. Option C would cost $14 million over five years and would include all of Option B plus still more wetland and fauna studies and a more comprehensive look at mitigation measures.

With regard to scope, on the scale of natural disasters, the 2011 floods certainly were not as severe as Hurricanes Katrina, Sandy, or Irene, but damage was substantial. Flooding affected approximately 4,000 homes and led to almost $88.5 million in damage. Quebec bore most of the damage with over 2,500 homes affected and $70 million in damages. Measures that could alleviate future flooding for these populations would be welcome.

How likely is future catastrophic lake flooding? The events on Lake Champlain of spring 2011 were unprecedented in scope and duration. Never before in 150 years of record keeping had lake levels exceeded 102.1 feet above mean sea level, yet in 2011 the lake reached 103.27 feet. Wind and wave damage occurred at elevations even above 103 feet. The lake stayed above flood stage for 67 days, finally receding below flood level on June 19. By some estimates, the flood represented a 500 year event, meaning there is only 0.2% chance it could happen in any given year.

On the other hand, lake flooding, though not as extreme, does occur regularly. The IJC report noted that they have been asked to consider solutions to lake flooding approximately every forty years. The last involvement on this question occurred in the mid 1970s and led to an equivocal recommendation that lake level regulation was feasible but it should be left to the governments of Canada and the United States to determine whether it was desirable. The governments, by their inertia, determined regulation was not desirable.

There has been some discussion about whether flooding will become more likely as a result of climate change. Certainly the area does receive more precipitation now than it has in the past. However, the timing and form of that precipitation will have a great impact on lake flooding. Lake flooding is driven primarily by snow melt and rain on bare ground when vegetation can not absorb it. So if increased precipitation comes in the winter, flooding could increase, but if it occurs in the summer, flooding is less likely. Additionally, if climate change means less snow, then the chance that an entire winter’s worth of precipitation gets stored until the spring thaw decreases. In short, there is no easy answer to how climate change will affect lake flooding.

The costs of preparing for the next flood depend on the measures considered. Two types of measures discussed include lake-level regulation and management of flood plain development. In addition to economic costs, lake-level regulation would have impacts on fish, wildlife, and wetlands in Lake Champlain. Management of development would arouse concerns about property rights.

The Lake Champlain Committee has recommended the workgroup pursue only a limited suite of the proposed studies. In particular, the group should avoid any studies that might lead to lake level regulation. LCC does not anticipate that these studies would lead to a different conclusion than those conducted during the 1970s. LCC has long been opposed to lake level regulation because of the high ecological costs associated with regulation. The IJC will need to find a responsible, prudent path forward that helps communities cope with occasional future floods while respecting and protecting the environmental integrity of Lake Champlain.