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Winona County and its hallmark hills and valleys provide a unique landscape into which farms, homes, and businesses are tucked, and at which tourists and residents alike point binoculars and camera lenses to soak up incredible views. Some feel that the county should use regulations to protect the most visible blufftops and steepest slopes, while others fear that those protections would hinder property rights and limit development within an already limited terrain.
County leaders have batted around the idea to use Geographic Information Systems (GIS) programming to help identify the blufftops and areas that would be most visible from below to assist in protecting those views. Called a viewshed analysis, the tool can help determine from where a proposed development site could be seen, thereby assisting county planners and landowners in finding the least visible building sites.
But there has been disagreement among both the County Board and county planning staff about how objective the tool could be, and whether its use would provide data that could be fairly applied to all bluff building proposals. After the board debated its use and county planners claimed they didn’t yet have a formula to use the programming in an objective way, board members voted earlier this month to pull language about viewshed analysis use from the proposed zoning ordinance.
Instead, the board asked that staff study the mapping tools at a later date, then present the board with the information within three months of the zoning ordinance final adoption.
Planning Director Brian Bender told the board that without defined perameters about what vantage points and corresponding views the board would like to protect, using viewshed analysis as a tool could result in inconsistent applications of the information and potential varied treatment of proposed developments.
When the vantage place is applied to a building site, a map can be produced which will show all of the spots down below that would be able to see a proposed development.
But there are plenty of blufftops that overlook lowlands without roadways or other frequented spots, some have argued. Thus, viewshed analysis, to be applied fairly, should have some specifics as to what, and from where, it is aimed at protecting.
For instance, the County Board could produce a policy that says a new home should not be visible from highly traveled roadways for more than one mile. Then, county staff could produce a viewshed analysis for a particular building site, and see where the viewable “shadow” falls to determine if the new structure would be visible for over one mile of the roadway. It’s that kind of detailed application that the viewshed idea is lacking, said Bender.
The board had discussed trying to identify the most highly-traveled roadways for use within a viewshed analysis policy, but the discussion never really produced any details.
Organized bluff advocate group BLEW (Bluff Land Environment Watch) objected to removing the analysis from the proposed zoning ordinance altogether. The group sent a memo to County Board members which highlighted an apparent disagreement among county staff on how effective viewshed analysis can be.
Winona County’s GIS Technician Nick Meyers, who is the county employee trained to use viewshed analysis programming, recently wrote an article in the winter issue of The Newsletter of the MN GIS/LIS Consortium entitled “Using LIDAR Data to Update Winona County’s Zoning Ordinance.”
The article addresses the previous proposal to include viewshed analysis for the areas with the most potential to affect views within the Mississippi Valley and one mile from the Highway 61 median. Under the old proposal, the viewshed analysis would have been done for developments that fall within 300 feet of the tops of bluffs within that one-mile corridor as part of a Conditional Use Permit (CUP) review.
“This will allow decision-makers to know more precisely how visible a proposed structure would be from nearby areas,” wrote Meyers. “The DNR’s ‘LAS to Contour 9.3’ tool, available in the DEM tool set, assisted Winona County in this process; it creates a first-return DEM that includes all vegetation and structures providing for a more accurate representation of the lines of sight when the viewshed tool is used in Spatial Analysis.”
A viewshed analysis that identifies vegetation and other structures shows an emerging technology that has taken strides since the city of Winona discussed its own bluff protection ordinance and related application of viewshed analysis. Within the city’s discussion, the lack of accounting for vegetation and other structures within the city’s analysis was identified as the major problem for viewshed analysis use as an absolute tool, even though the city did decide to use the technology in considering new developments. The county evidently has newer technology that avoids the city’s problems with viewshed use.
The County Board is expected to hold its final public hearing on the proposed zoning ordinance in the coming weeks, with final adoption of the ordinance expected to follow. Discussions on the role that viewshed analysis may play in bluff developments will likely come in the fall.
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