How is climate change affecting river flooding in Maine?

The Kennebec River in Augusta and Hallowell noticed near-record-high flooding earlier this week as inches of rain fell throughout Maine and New Hampshire.

In accordance with the Nationwide Climate Service, the Kennebec crested at simply over 20 ft on the downtown Augusta gauge early Tuesday morning. Social media posts, just like the one pictured above, present how the swollen river overtopped its banks and spilled onto adjoining roads earlier than beginning to recede.

The Kennebec River gauge in neighboring Hallowell recorded a crest of 16.6 ft across the identical time, properly above the opposite highs on report in that spot (although this information is extra restricted, as this gauge doesn’t have year-round forecasting).

“That flood in Hallowell was significantly impactful. Some water received into some first-floor buildings,” stated meteorologist Jon Palmer within the NWS’s Grey workplace (try Spectrum reporter Susan Cowl’s images of that flooding).

“Throughout Kennebec County — simply a variety of excessive water, water within the floodplain, low-lying areas,” Palmer stated. “(We had) 4-6 inches of rain in a single day Sunday night time. That’s a variety of rain for our space.”

Rain and river flooding, particularly harmful flash flooding, are inextricably linked, particularly in developed locations with extra onerous surfaces that don’t shortly take up stormwater runoff. The Nationwide Oceanic and Atmospheric Administration says on its extreme climate fundamentals web page that flooding kills extra folks within the U.S. yearly than tornadoes, hurricanes or lightning.

“Flash floods happen when heavy rainfall exceeds the flexibility of the bottom to soak up it,” NOAA says. “In addition they happen when water fills usually dry creeks or streams or sufficient water accumulates for streams to overtop their banks, inflicting speedy rises of water in a brief period of time.”

It’s necessary to emphasise that nobody climate occasion may be attributed to local weather change with out complicated modeling to see whether or not it will have occurred the identical manner in a world that didn’t have rising ranges of greenhouse gasoline emissions trapping warmth within the environment.

However analysis does present that local weather change is inflicting rainfall to extend in amount and depth throughout the nation and particularly within the Northeast.

“Additional will increase in rainfall depth are anticipated (within the coming a long time), with will increase in precipitation anticipated throughout the winter and spring with little change in the summertime,” scientists wrote within the Northeast chapter of the 2018 Nationwide Local weather Evaluation, or NCA. (The following installment on this sequence is due out this yr.)

The Kennebec Journal’s editorial board took this up within the aftermath of this week’s rains, writing on Wednesday: “Prefer it or not, the local weather disaster is coming. For these on the Maine coast and alongside our tidal rivers, it’s already right here. If we in Maine don’t do our half in limiting its impact on our communities, how can we ask anybody else to do theirs?”

Knowledge from the Maine Local weather Workplace reveals that in 2022, the state noticed almost 8 inches extra rain as in comparison with the typical for the final century. The biggest anomaly in elevated rainfall has been recorded within the fall season.

Most of Western Maine received a month’s price of rain prior to now week, the NWS said on Twitter Thursday.

Elevated temperatures trigger extra moisture within the air, however that’s not the one issue that drives spring river flooding. Maine’s shifting seasonal timing and snow patterns additionally play a job. In truth, per the NCA, an rising sample of earlier snowmelt and a shorter snow season could result in decrease spring stream flows, which might assist mitigate flooding.

This ties in to the results of the rain we noticed this week. Palmer, the meteorologist, stated this occasion’s comparatively delicate impacts are partly defined by its later-spring timing, which got here after the majority of the spring snowmelt.

“We did luck out that this occurred now and never earlier within the spring, the place we had a very deep snowpack. The impacts might have been considerably worse,” he stated. “While you mix snowmelt on prime of this quantity of precipitation, that will in all probability immediate a variety of rivers to a minimum of go into reasonable (flood) stage and perhaps into main stage too.”

Lots of Maine’s highest river ranges on report got here in spring 1987, an occasion fueled by a mix of rain and snowmelt, in accordance with the NWS. Spring 1936 is one other instance, the place excessive snowpack underneath a stalled rain system induced harmful ice jam floods and set data all through New England.

In early March, the Maine River Stream Advisory Fee put out its annual evaluation of those spring soften hazards — and located few to report. There was much less river ice than regular for that point of yr, stated fee co-chair Nicholas Stasulis of the U.S. Geological Survey in a information launch, owing to excessive stream flows within the fall and early winter and excessive temperatures in January.

 Storms anticipated to change into extra frequent, damaging as sea ranges rise

Inland or coastal flooding at any time of yr can wash out roads, overwhelm culverts and have an effect on recreation infrastructure. Even New Hampshire’s Kancamagus Freeway and the Mount Washington Auto Highway took injury on this week’s heavy rain and, at these larger elevations, snow. Maine ATV trails will stay closed by means of Memorial Day because of the rain in an extension of mud season.

Floodwaters threaten folks in addition to infrastructure. Wardens rescued a girl from a half-submerged automotive alongside the Crooked River in Waterford because the rain fell on Monday night time. Keep in mind — flip round, don’t drown.

Maine’s 2020 local weather plan stated the state would search federal approval this yr for a climate-focused replace to its Hazard Mitigation Plan. The local weather resilience and infrastructure features within the local weather plan itself targeted largely on coastal flooding, together with the official requirement that state development initiatives plan for 1.5 ft of sea degree rise by 2050 and 4 ft by 2100.

The local weather plan additionally acknowledged the dangers of riverine and rain-driven flooding locations like Central Maine. The plan included expanded grant applications for fixing undersized and flood-prone culverts and creating different “climate-ready infrastructure” — a idea I coated a number of years in the past in New Hampshire, on a flood-prone salt marsh crossing I drove usually.

In an replace final December, the state highlighted a grant-funded stormwater overhaul slated for development this yr in flood-prone Winslow (web page 51), which sits throughout the Kennebec River from Waterville. The state’s report stated components of the city, the place the decades-old drainage system had “reached the top of its helpful life,” had been liable to flood in something over 2 inches of rain per hour.

Should you dwell close to a stream crossing that ceaselessly floods in heavy rains, verify the listing of state grants introduced in March to improve undersized culverts. Flooding, as we’re seeing with these rain-driven river floods, is not only a coastal challenge. Extra of those initiatives might be wanted as Maine continues to get wetter.