Geologist briefs Pine County board on Snake River geology, erosion risks and land‑use links to water quality

County officials heard a geological briefing on the Snake River watershed that linked deep geology, glacial history and modern land uses to river erosion and water quality. Carrie Jennings, a consulting geologist who mapped Pine County, said bedrock variations and glacial deposits determine where the river meanders, where lakes and low‑gradient reaches form and where bluffs are vulnerable to failure. Jennings explained that parts of the county are underlain by basalt flows and by Permian and older sandstones and that glacial tunnels and fans created low‑gradient reaches and sediment sources. She noted that some reaches near Cross Lake and downstream toward the Saint Croix show active incision and nick points, contributing to bluff erosion in places that are sometimes developed for waterfront housing. On managing risk, Jennings recommended vegetation‑based slope protection, setbacks from the top of bluffs, and limited clearing. "The best strategy for reducing risk of slope failure and loss of property is to avoid placing structures too close and to maintain vegetation to stabilize the slopes," she said. She discussed examples where riprap has been used to stabilize banks but cautioned that natural woody cover can provide longer‑term, ecologically beneficial protections. Jennings also described how land uses such as row‑crop agriculture and concentrated animal feeding operations can increase runoff and contaminants; she noted that shallow, sluggish reaches can warm in summer and show bacterial impairments where animal agriculture is present. Commissioners asked about aquifer vulnerability near the Mount Simon (Mount Simon isostratigraphic references); Jennings said the Mount Simon (if present in small thickness in the county) is thin and that susceptibility maps in the county geologic atlas should be consulted for specific contamination risk. The board did not take action on the presentation; staff said the geology briefing was intended to inform watershed planning, trail siting, shoreline management and future regulatory conversations.