Published on March 11th, 2019 | by Carolyn Fortuna0
“Wildly Fluctuating Forecasts” & Flooding — A Common Theme Of Climate Change | #CleanTechnica Exclusive
March 11th, 2019 by Carolyn Fortuna
Want to interpret and apply scientific understanding to an extensive array of climate datasets? Then head over to the National Oceanographic and Atmospheric Administration’s (NOAA) National Center for Environmental Information website. It’s filled with US climate normals, monthly climate reports, and drought information. You can find analyses of weather and climate events, placed into proper historical perspective, with emphasis on understanding their unusualness and comparing recent events to expectations of future climate conditions. Regional, sectoral, and even international connections that expand our understanding of the earth’s climate are there, too.
It can also be really helpful to put this data into perspective personally. We at CleanTechnica were fortunate enough to have access to the NOAA hydrologist-in-charge at the NE River Forecast Center, David Vallee, who described that climate data and put it into a relevant perspective for us. Importantly, Vallee analyzed today’s “wildly fluctuating forecasts” as a symptom of climate change.
Climate is defined by NOAA as long-term averages and variations in weather measured over a period of several decades. The Earth’s climate system includes the land surface, atmosphere, oceans, and ice. Many aspects of the global climate are changing rapidly, and the primary drivers of that change are human in origin. Evidence for changes in the climate system abounds, from the top of the atmosphere to the depths of the oceans. Vallee demonstrated what this climate change looks like on the local level as the keynote speaker at the 2019 Land and Water Conservation Summit at the University of Rhode Island. The title of his speech was, “Conservation, Meet Development: The Role of Land & Water Protection in Building Resilient Communities.”
Consistent with NOAA’s analysis that impacts related to climate change are already evident in many sectors and are expected to become increasingly disruptive across the nation throughout this century and beyond, Vallee spoke specifically about the role of building resilience in the face of a changing climate. An engaging speaker who molded data with relevant local stories, he described how, at age 52, he has seen significant and startling differences over the course of his career in the way that our rivers and streams rise and fall.
He outlined that changing flood behavior now is triggered by multiple day weather events, flash floods, waste water choking pipes, slow and steady beach erosion, and sea level rise that punches more intensely at the lunar tide. These elements of climate change aren’t entirely recent, however. As early as 1982, with dramatic, quickly changing weather and flood conditions, Vallee knew, “There’s something big going on here. We’re not getting the forecasts we want out there soon enough.”
The 100-Year Rainfall Event
While northern New York and northern New England experienced dry conditions during 2018 autumn, the rest of the region was exceptionally wet. In fact, the Northeast had its wettest autumn since 1895. Ten major climate sites also had a record wet autumn. The climatology of very large precipitation events is a critical component of engineering design and regulations for structures and facilities that must withstand or protect against such events. These events can produce localized urban and widespread flooding with damage to property, degradation of water quality, and potential loss of life.
A 1% weather event’s likelihood of happening — that’s the original definition of the 100-Year Rainfall event. Since that definition takes into account much less intensity and volume of rainfall, the 100-Year Rainfall event is now a “misnomer,” Vallee described. He used the southern New England river basin as an example. With normalized numbers of minor, moderate, and major floods, the frequency of what would have once been termed the 100-Year Rainfall event has changed significantly since 1970. In 2018, there were 22 days recorded in which more than 1 inch or more of rain occurred at TF Green airport, which serves the metro Providence, Rhode Island area.
“In 2018, we had over 70 inches of rain” in Rhode Island, he continued. The frequency of more than 50 inches of rain annually is increasing.
Indeed, Cornell University research points out how previous climatologies have been based on the premise that the extreme rainfall series do not change through time. So we assume that older analyses reflect current conditions. Recent analyses show that this is not the case, particularly in New York and New England, where the frequency of 2-inch rainfall events has increased since the 1950s, and storms once considered a 1-in-100 year event have become more frequent.
Such storms are now likely to occur almost twice as often. “Folks, we aren’t built for this. As a result, we’re seeing more flooding.”
Flooding — Now a Common Event Due to the Oceans’ Rise
Infrastructure is being damaged by sea level rise, heavy downpours, and extreme heat. “Tide cycle after tide cycle, eroding the dunes, washing the sand across Atlantic Avenue” — these were the effects of 2012 Hurricane Sandy in Rhode Island. “Go down to Roy Carpenter’s Beach. The dunes are gone. There’s nothing there. That’s how vulnerable we are on the coast. There are a lot of tough decisions to make — it’s all about the tax base. How do we successfully mitigate the coastal effects of climate change?”
Damages are projected to increase with climate change. In communities that did not provide adequate stormwater drainage systems in their early design, flooding and associated costs have become frequent. In communities that have dedicated their land for urban development, flooding has been consistent with sea level rise. “Over the next 50-60 years, we’re expecting to see 1.5 – 3 feet sea level rise,” Vallee predicted.
2018 continued the record global ocean warming. Vallee showed us what that meant, pointing to the reach of the Arctic ice cap in September, 2018. By January, it was, in comparison to previous years, “a lot thinner … on a global scale, that difference in temperature is what drives the jet stream.”
Climatologists have determined that the jet stream often gets “more blocked up.” Slow moving weather systems that are the result of this blockage create “saturated antecedent conditions before the actual main event.” Each weather event is fed by a tropical connection, and it’s like “playing in a warm sandbox.” Storms can now sit for 3 days, or multiple massive weather events can take place, one after the other, in just a few weeks.
The Northeast is averaging about .3 degree warming every decade, Vallee noted. “When you increase temperature over 1 degree, you move a latitude. We’re going south,” he synthesized. The number of days below zero degrees is shrinking, and the number of days over 80 degrees is increasing. The lack of cold prohibits regional mechanisms to drive off invasives. “When you talk about the trees, when you talk about the insects — everything is moving.”
Prior to the 1970s, there were several multi-year droughts. “The droughts don’t look like what they used to. We are getting more intense events. Now we have ‘flash droughts’ in which we have summertime extended periods of drought bookmarked by intense rainfalls in spring and fall.”
Best Practices | Final Thoughts
“Flood control works,” Valley stated. A body of water like the Scituate Reservoir, Rhode Island, was designed as a water supply in the early 20th century and was never intended for flood control. It is now confronting peak holding capacity in March, and it has no transpiration mechanism to help move the water out before the subsequent high precipitation spring period. “Sandy soils get you only so far; the sponge can handle only so much,” he said.
Not to give up, Vallee pointed to the Netherlands, where they have implemented a flood control mechanism titled Protect, Adapt, or Retreat. Can they protect the area to survive the next weather event? Can they adapt the surroundings to mitigate the buffer they took away? Should they retreat from building on the beach where they will certainly lose the dunes in the next 20-30 years?
Vallee offered a framework of adapted strategies for Northeast communities to incorporate in order to plan for flooding in comparable ways.
- Preserve the land.
- Retain and restore grounds to their natural state.
- Increase rainfall/ runoff storage capacity of a given parcel of land.
- Improve water quality through restoration of lands.
If you’re wondering about some specific data about consequences of global sea levels rise, check out for yourself weather data and generate your own data patterns at NOAA’s Climate Change at a Glance website.