10.b River Taskforce Letter 21
k.cammilleri
Subject:St. Croix Boat Traffic
Attachments:IMG_0158.jpg; St Croix Flows.png
From: Chauncey Anderson
Sent: Tuesday, May 18, 2021 11:37 AM
To: c.maefsky <c.maefsky@ci.scandia.mn.us>; k.cammilleri <k.cammilleri@ci.scandia.mn.us>
Subject: St. Croix Boat Traffic
Hello Mayor Maefsky and Scandia City Council,
This brief note is intended to inform tonight's city council meeting's agenda item regarding issues on the river.
For background, my family lives along the river north of Marine and has done so for over 100 years. I grew up
on the river and have watched the boat traffic and its changes over the years. My life on the river led me to a
career in hydrology and water quality, and I currently work as a Water Quality Specialist for a federal agency,
with studies on turbidity, sediment erosion and transport, and assorted nutrient issues including Total Maximum
Daily Loads (TMDLs) and eutrophication (e.g. algal blooms).
Over the last 5 or so years, I and my family members have witnessed a striking increase in river traffic of
large boats going very fast and creating large wakes. Aside from the aesthetic issues (see below) I've become
convinced that the increased traffic and associated wakes are causing unprecedented erosion and actively
undercutting trees and other riparian vegetation, which in turn causes additional erosion. The bank at our
family's property has lost about 3-5 feet in recent years.
As a water quality professional and with my specific areas of study, this observation leads me to suspect that
the erosion and associated sediment and likely nutrient transport could be a large contribution to the
river's phosphorus load downriver into Lake Pepin. As you're aware, that lake has issues with harmful algal
blooms (HABs) and is one rationale for the St. Croix River's TMDL on phosphorus. In an era where nutrient
delivery from farms and runoff is a challenging problem, reduction of wake-caused erosion is a tractable and
solvable problem. I believe the rules are in place to do so, and they just need to be enforced, likely with some
educational campaigns as well.
I should note that I've looked at this issue from the standpoint of the relatively high summer flows in the river in
the same timeframe. I did confirm using online tools (and see attached image) that the river has experienced
disproportionately high flows in recent years, but I don't believe it's simply those high flows that are causing the
erosion. Instead I think the high flows enable the larger boats to use the river during the summer which then
causes the erosion. I've looked at the shoreline and do not see evident erosion simply from the flow, but when a
large boat goes by the calving of sand and clay from the shoreline is obvious and leaves a small shelf where the
wake hits the shore, with turbid plumes of sediment being transported into the water column.
There are annoying / nuisance aesthetic issues as well, including noise, safety, nightime lights and associated
noise from generators, power boats going through the sensitive slough habitats (and cutting out downed wood
that blocks channels). These would all be addressed with enforcement of the no-wake zone.
Thank you,
2
Chauncey Anderson
20453 Quinnell Ave N
Scandia, MN. 550973