When Record-Breaking Is the Norm: Mitigating the Effects of Extreme Rain Events in an Altering Environment
by
Kai Kornhuber, Mona Hemmati and Andrew Kruczkiewicz|September 20, 2021
This story was published as part of our Climate Week NYC coverage. Find out more about Climate Week, read our other stories, and inspect out our upcoming occasions.
Flooding in Belgium, July 2021 Credit: Régine Fabri
Torrential rainfall rapidly changed New York Citys streets and expressways into rivers and lakes on Wednesday night September 2, 2021, shutting down the entire metro system (the first time given that Hurricane Sandy) and forcing traffic throughout the city to come to a halt. In a nonstationary environment due to ongoing anthropogenic climate modification, we will see more events like this. Mitigation procedures should be prioritized to address the increasing threat from ever increasing frequency and magnitude of rainfall extremes.
Comparable to previous extreme flooding occasions, the rainfall was brought by the remains of a tropical storm, Ida, which prior triggered prevalent flooding and devastation to Louisiana. The occasions make up the 3rd major flooding occasion in NYC within simply a few months, after residues of tropical storm Elsa brought uncommon rains and strong winds to the city in early July.
From a global perspective these citywide disasters didnt occur in isolation, but belonged to a series of high effect flood occasions that made record-breaking the norm of 2021. Simply after Elsa brought anomalous rain to NYC, a significant storm system stalled over Western Europe on July 14-15, causing record-setting rains over the Low countries, Germany, Switzerland, and France. Some parts of Germany got 2 months of rain in one to two days, which triggered rivers to overtop their banks and flash flooding through communities. This extreme event resulted in extreme insured losses of around 4.7 to 5.9 billion euros from the floods in Western Germany alone..
Simply a week later, on July 19 and 20, severe flooding took place in the main Chinese Province Henan after record breaking rainfall of more than seven inches was determined in the provincial capital Zhengzhou. The floods that affected big parts of central China triggered a minimum of 300 casualties and forced more than 800,000 individuals to evacuate..
In August, a series of thunderstorms caused severe rains in Turkey that resulted in a number of floods and landslides. Throughout the course of the week that included unprecedented regional water increases by 4 meters, at least 81 people lost their lives, and more than 1,800 were left.
Extreme Rainfall and Stagnating Weather in a Changing Climate.
Tape breaking rainfall extremes in general and short duration rains events in particular are increasing in frequency in a warming climate as the rate of evaporation and the environments capability to hold water both increase. Physically, these relationships are well understood and an increase in local rains extremes can be discovered in observations worldwide and at a regional scale leading to a boost in flood damages within the historical datasets and under future high emission forecasts. To express the Germany flooding occasion from an environment modification point of view, the quick attribution research study from the World Weather Attribution Project discovered that the occasion was made 1.9– 9 times more likely by environment modification.
Flooding in the Bronx the day after Ida travelled through New York City. Credit: Jim Griffin.
In addition to thermodynamic factors that increase the probability of record-breaking rainfall extremes, atmospheric dynamics typically contribute in making a severe weather condition occasion more severe. When sluggish moving weather condition systems trigger associated rainfall to happen over the very same region for a longer duration, local flood risk can enhance. Among the most popular examples of recent years is Hurricane Harvey, which stayed stationary over Texas, directed by a relentless meander in the jetstream, consequently causing severe flooding in Houston mid-August 2017. Likewise, the low-pressure system connected with the German flood in 2021 remained fixed. Evidence recommends that climate modification is one of numerous aspects in shifts in atmospheric dynamics, such as the weakening of the mid-latitude blood circulation over the past 4 decades, leading to slower storms and extreme precipitation events more frequently. The 2021 record rains occasions in New York were not due to a particular slow moving weather system, the massive blood circulation played an important role by providing additional wetness to Tropical Cyclone Ida through the interaction with an extratropical front when it made its way to the northeast..
Mitigating Flood Risks in a Changing Climate.
Effects from climate extremes do not occur in seclusion to other non-climate related social challenges and typically function as an enhancing force. COVID-19 hospitalizations in Louisiana were close to their all-time high prior to Ida struck, making evacuations and possible health support more challenging. Much of those that passed away in NYC drowned in prohibited below ground houses, a last haven to prevent displacement from the citys high rents. The record-setting per hour rains rates of 3 inches or more made the waters rise at speeds difficult to leave..
In addition, urbanization as a result of population growth and economic advancement includes more resistant surface areas to the area leading to increasing runoff and altering the attributes of floodplains, flood depth, and flood degree. Urban growth and informal development results in not just increased exposure, but increased direct exposure to currently underserved populations with lower coping capabilities.
For protection of existing and future generations, and to decrease the opportunities of future occasions leading to devastating effects, 2 types of mitigation steps can be adopted. An useful example of such measures is the brand-new levee system in New Orleans that was constructed after Hurricane Katrina. Every storm is different and while a success for Ida, concerns remain: are these measures enough considering the altering nature of the hazard?
As the frequency and intensity of flood occasions are increasing due to climate change, protective structures– referred to as structural mitigation measures– that are developed based on contemporary flood dangers, may experience future extreme occasions that cause overtopping or failure of the structure. Such methods may also create an illusion of safety, additional promoting growth in or near flood-protected areas, in addition to promoting a lack of proper threat understanding at the person, institutional and government levels.
Nonstructural flood mitigation measures count on public policy preparation, such as land-use, acquisition and zoning policy, and socioeconomic incentives that focus on controlling the exposure. These policies are most efficient in urbanizing neighborhoods, however, they are not as successful as expected in reversing the tendency of individuals to select to reside in flood-prone areas.
Important concerns in that context are: what level and mix of nonstructural and structural steps should be carried out to help future neighborhoods be more durable to devastating floods and extreme occasions like the one that occurred September 2, 2021 in NYC? And further, to what extent are these steps supporting one group of people more than others? Is this disproportionate benefit leading to the disadvantaged populations becoming relatively more disadvantaged?.
In some regions, the magnified frequency of severe weather occasions makes it significantly challenging to recuperate, let alone to effectively prepare for the next extreme, making retreat the only practical option. This is easier said than done as numerous questions around which neighborhoods are focused on, and around optional vs. obligatory retreat must be dealt with. And finally, we must know not only what we are pulling back from, but what hazards (existing and future) may be encountered there when we show up..
Flash flood danger is much more complicated to delineate, and we need to interact if, and to what extent, individuals are pulling away from one hazard into another one. This tension, both with flash floods, other specific dangers, and compound risks, will be one of the components that should be addressed.
With Climate Week taking place in New York City at the minute, we have the duty and a chance to ensure a connection is re-established with the most vulnerable populations, especially in city areas such as NYC where gradients of wealth and privilege exist. Today is an opportunity to make sure the activities/discussions/policies are established at an appropriate granularity that address disproportionate effects, such as what we saw in NYC just a brief couple of weeks ago.
Comparable to previous extreme flooding occasions, the rains was brought by the remains of a tropical storm, Ida, which prior caused widespread flooding and destruction to Louisiana. The occasions make up the third major flooding occasion in NYC within simply a couple of months, after remnants of tropical storm Elsa brought unusual rains and strong winds to the city in early July. Tape-record breaking rainfall extremes in short and general period rains occasions in particular are increasing in frequency in a warming environment as the rate of evaporation and the atmospheres capacity to hold water both increase. To reveal the Germany flooding event from a climate change perspective, the fast attribution research study from the World Weather Attribution Project found that the event was made 1.9– 9 times more most likely by climate change.
In addition to thermodynamic factors that increase the possibility of record-breaking rainfall extremes, atmospheric dynamics typically contribute in making a severe weather occasion more extreme.