Infrastructure in the 21st Century: Coastal Inundation is More Than a Nuisance

Several cities in the United States are already experiencing the effects of nuisance flooding and rising sea levels means even more coastal infrastructure will be at risk in the near future. Are U.S. coastal towns and cities ready for more frequent incidents of nuisance flooding?

Even though California is in a drought emergency, San Francisco has seen a 364 percent increase in the incidents of nuisance flooding, but they are not alone. During astronomical high tides, some streets in downtown Charleston, SC, some streets become streams due to so-called “nuisance flooding.” Other cities, such Washington DC and nearby communities, are also at risk of the effects of nuisance floods. Are more cities going to be at risk? If so, are they making plans to avoid the infrastructure damage caused by frequent exposure to salt water?

The Effects of Sea Rise are Already Apparent

In the December 2014 issue of the journal Earth Future, two NOAA scientists looked historical patterns of nuisance flooding and used them to predict future incidents. What were their findings?

Incidents of Nuisance Flooding Increased During the 20^th Century

As illustrated in Figure 1, the incidents of nuisance flooding not only increased between 1920 and 2015, but the rate of coastal inundation accelerated. For Atlantic City, NJ, Baltimore, MD, Annapolis, MD, Wilmington, NC, Port Isabel, TX, and Honolulu, HI, the incidence of nuisance flood increased tenfold. For Sandy Hook, CT, Philadelphia, PA, Norfolk, VA, and Charleston, SC the rate of coastal inundation increases fivefold.

Figure 1. Historical Rates and Acceleration of Coastal Inundation

The Frequency of Coastal Inundation Continues to Accelerate Throughout the 21^st Century

During the next 60 years, many coastal cities in the United States will reach the point where the frequency of nuisance flooding will cause significant degradation of critical infrastructure, such as storm water drainage and roads, and the population will start to migrate. Figure 2 illustrates the projected timeline for the tipping point for San Francisco, CA and Norfolk, VA.

Figure 2. 21^st Century Acceleration of Nuisance Flooding and Tipping Point Forecast

East Coast Cities Most Affected by Nuisance Flooding in the 21^st Century

As shown in Figure 3, only three cities on the West Coast will be affected by the accelerated increased rate of coastal inundation, while numerous cities along the East Coast will experience significantly higher incidence of nuisance flooding. In fact, some coastal towns and cities are already experiencing the effects. What actions are these areas to mitigate the effects of nuisance flooding?

Figure 3. Timetable of US Cities Reaching the Tipping Point of Rapid Increases in Nuisance Flooding

The Responses to Increased Incidence of Nuisance Flooding: Mitigation and Denial

A recent MIT report indicates only 53 percent of coastal cities are planning to take action to mitigate and adapt to the effects of climate change. While in some cases, some cities find the costs associated with taking a proactive approach to increased nuisance flooding prohibitive, others simply deny that sea level rise is an issue. In South Carolina, they are rapidly accelerating the development of coastal areas. Maryland , on the other hand is taking action to mitigate the effects of coastal inundation. Whether coastal regions prepare for increased nuisance flooding or have to react to it in the future, the demand for traffic and civil engineers will rise along with the seas.