Norwich — Fifteen residents, many of whom own property in a floodplain, showed up to a Planning Commission meeting on Thursday night to learn more about how a set of proposed river corridor regulations could affect their safety — and their wallets.

The Planning Commission and municipal Planning Director Rod Francis were gathering initial feedback and information about the possibility of updating the Town Plan to adopt language recommended in the Vermont River Corridor Guide.

Generally speaking, the change would make it more difficult to develop land along the town’s rivers and streams, though there are complicating factors involving Act 250 (which governs the state’s large developments), and the geographic scope of the proposed state model ordinance.

The land already is subject to two different levels of protection — federal FEMA floodplain guidelines, as well as a 2009 ordinance, adopted by the town, which establishes development buffers of between 50 and 100 feet from the riverbank, depending on the waterway.

But the state model, which is based on analysis of long-term erosion patterns, takes into account where the river will lay in the future.

“That’s how the valley got flat. If you’re on one side of the valley and the river is on the other side, eventually it will come over,” Kevin Geiger, a senior planner with the Two Rivers-Ottauquechee Regional Commission, said during a phone interview on Wednesday.

Because FEMA regulations are based on flood heights, Geiger said, they don’t account for meanders, which can undercut the earth from beneath a lofty structure.

“That doesn’t matter if the river comes underneath you,” Geiger said.

During the meeting, former state Senate majority leader John Carroll said that his own house falls within the affected area.

“The floodway looks like it lays on about 3 percent of our property,” Carroll said. “The floodplain … that’s probably more like 5 percent of our property. The buffer zone adopted in ’09 affects about 10 percent of our property. The river corridor plan would involve about 50 percent of our property, all of which is developable.”

Updated in 2010, the 60-page Vermont River Corridor Guide is organized around the concept of maintaining a river’s equilibrium.

In a perfect world, the amount of organic debris and settlement that is eroded from a stretch of river is equal to the amount of sediment that’s deposited, which keeps the river relatively stable. It will meander somewhat, as it constantly course-corrects imbalances.

Upset that balance — by, say, stabilizing a riverbank to prevent erosion — and the river’s capacity to cause damage increases accordingly.

“River management has become a vicious cycle where flood recovery and structural constraints have led to increased encroachments and land use investment where rivers formerly meandered and accessed their floodplains,” according to the state river corridor guide, which called constant efforts to artificially control river flows costly and unsustainable. “Inevitably, and often decades later, a large flood occurs and the cycle repeats itself.”

Francis said that some people living near a stream or river shouldn’t “reasonably expect a variation in the streambed in your lifetime, or in your grandchildren’s lifetime.” But in other areas, he said, if “there’s a microburst, all bets are off. Because it could change course really dramatically.”

The question, Francis said, is which set of river protection plans better girds property owners against that eventuality.

At this stage, he said, “I don’t know the answer to that question.”

There are some factors that make it difficult to say which plan offers more protection, which is more restrictive of development, and which will cost more for stakeholders.

The state model ordinance is based on a state-produced floodplain map, which only concerns itself with watersheds of at least two square miles. If the town were to adopt the model, there would be less protection against development in those smaller areas than currently exists.

Another wrinkle is that properties that are subject to Act 250 permits already are held to the state river corridor standards, and Francis said thus far he has been unable to find a listing that accurately describes which properties meet that description.

The state also offers towns an incentive to adopt its ordinance — right now, when a federal disaster zone is declared in the county, the town must pay 12.5 percent of the cost to repair public infrastructure. If Norwich adopted the state model, it would only have to pay 7.5 percent, which would have made a $200,000 difference in the case of last year’s July 2017 thunderstorm.

However, Francis and Planning Commission Vice Chairman Jeff Goodrich said the town currently is arguing to the state that its existing protection plan is strong enough to allow it to qualify for the incentive, and that negotiations are ongoing.

Chairwoman Jaci Allen said that if the town did realize that benefit, it would reduce the potential burden on taxpayers.

“We all pay property taxes,” she said. “So we’re all affected to some extent.”

Geiger said other towns in the Upper Valley are undergoing similar discussions, and that Bethel, for example, adopted some of the language from the state model. However, Geiger said, he was unaware of a town as developed as Norwich adopting the guidelines.

Francis said that, before the language could be adopted, it will have to go through a lengthy process, including multiple public hearings before both the Planning Commission and the Selectboard.

“We’re some months away, at best, from making a decision,” he said.

Matt Hongoltz-Hetling can be reached at mhonghet@vnews.com or 603-727-3211.