It's Worse Than You Think -- The Increased Risk Posed By Floods

Ever since Edison set up his little power company on Pearl Street in lower Manhattan in 1882, utility companies have been at risk from extreme weather.  Edison addressed the issue by convincing New York City to spring for underground cables, a more expensive way of delivering electricity than by poles but immune to wind damage.  That left the system vulnerable to underground floods, rare at the end of the nineteenth century in New York City.  Today, the risk of floods is much greater than it was in Edison’s day, which became crystal clear in the wake of the string of hurricane-caused flooding in 2017.  And while pictures of downed poles make the public focus on wind as the defining danger to the grid, flooding can be even more destructive and more challenging.  The fact is, over 70 percent of presidential disaster declarations in the past ten years involved flood-related events, including hurricanes, severe storms, and heavy downpours.

Unfortunately, the risk posed by flooding has been severely underestimated, as a recent study by scientists at the University of Bristol in England has made clear.  FEMA’s official maps of flood risk are based on maps of widely varying accuracy.  Some are old, some are of poor quality, and few cover smaller catchments, such as narrow rivers and streams.  The new map developed by the Bristol researchers suggests that the number of Americans exposed to serious flooding risk is 2.6 to 3.1 times higher than numbers based on the FEMA maps.  Interestingly, that does not take into account climate change; the paper focuses on freshwater flooding, not coastal inundation from rising sea levels.  The rise in the numbers reflects the map’s greater level of detail in spatial and data analysis, and includes more recent information about population and economic development.

As for coastal regions, the facts are very disturbing.  Major substations and power plants that supply electricity to more than 70 million people are located in coastal areas that are highly vulnerable to flooding from hurricanes, nor’easters and other severe storms.  As sea levels rise as a consequence of global warming, these areas will become even more vulnerable.  To take just two examples, it is estimated that a category 3 storm along the Delaware River Valley could leave as many as 79 major substations and more than 8,800 MW of generation vulnerable to storm surge and flood waters; similarly, in southeastern Virginia four power plants and 57 out of 132 major substations could fall victim to flooding.  The situation is similar in all coastal regions.

Utilities spend a great deal of time and resources planning for natural disasters, but these plans have been based on largely inaccurate information.  They typically account for their current location on a floodplain, but that information is outdated and fails to account for climate change.  Historical data are equally questionable in a time when hundred-year floods are occurring in ten- and even five-year cycles.  Redrawing maps based on the new data generated by the Bristol researchers and other updated information will help, as will accepting the reality that violent storms will continue to become more frequent.  Unfortunately, the steps needed for mitigating the threats posed by major floods are complex, expensive, and require long preparation periods.

The three main options are: to build seawalls, dunes and wetlands; to elevate substations or replace current equipment with submersible units; or to simply retreat from coastal areas or other places that are particularly vulnerable.  Nor is it possible for utilities, except those serving very limited geographic areas, to devise unified plans for all their assets because of the variability of the terrain most utilities operate in.  Surrounding the entire perimeter of generation and substation facilities with concrete walls and incorporating flood gates or barriers can help, but these sites are often remote and difficult to man during weather crises so these may be only a partial solutions. 

Some utilities have resorted to using mobile substations that can be used to quickly reconfigure a threatened area by bypassing damaged ones.  Adding redundancies can also help, but that’s an expensive option.  Maintaining existing and building additional floodplains can mitigate the threat of flooding, especially in inland locations,  although it’s essential to take into account future economic and building plans in the vulnerable area.  The flooding in Houston, for instance, was severely impacted by the proliferation of building over what, before recent massive construction in formerly rural areas, had been more than adequate floodplains.

Smart-grid technologies are promising.  Distributed generation and peer-to-peer sharing of solar installations can help isolate outages and ensure that emergency services have access to power.  Renewable sources, which don’t depend on the delivery of fuel over roads which may be impassable for days after severe flooding, can mitigate the threat of prolonged outages.  And smart meters can cut the time and expense of locating exactly where outages have occurred. 

Of course, traditional measures continue to be useful.  Burying power lines, Edison’s solution, can still work even in areas prone to severe flooding so long as the lines are encased in flood-proof, durable tubing.  Strengthening existing poles, trimming trees and diligently clearing flora and debris remain essential.  Most important, utilities must base their maintenance and building plans on up-to-date maps and data.  Relying on old FEMA and out-of-date local maps is a recipe for future disaster.