The two great rivers are hardly twins — that's obvious where they come together near Hastings, where the clear waters of the St. Croix merge with the mocha-tinted murk of the Mississippi. Despite the contrast, though, both have helped define the geography, economy and the history of the Twin Cities.

Now their respective futures, coincidentally, have also arrived at a pivot point.

For the first time since the 1970s, the two different sets of rules guiding development and protecting these two important waterways are facing major changes.

In the case of the Mississippi, the Minnesota Department of Natural Resources (DNR) is in the early stages of updating and rewriting regulations over development dating from 1979 along the 72 miles of river that wind through the Twin Cities, from Hastings in the southeast, through both downtown St. Paul and Minneapolis, to Dayton in the northwest.

On the St. Croix, meanwhile, a large shadow has been cast over future development decisions along the river. The city of Lakeland last month dealt the DNR its first setback since the state Supreme Court ruled three years ago that the agency did not have the authority it had presumed it had to overrule local zoning decisions in cases where they did not comply with the landmark Wild and Scenic Rivers Act of 1972.

The rules governing the rivers reflect their different characters, said Molly Shodeen, area hydrologist with the DNR. The Mississippi is an important transitway, for example. "A working river is not the same as a Wild and Scenic river, but it still has very high value," she said, and the rules are designed to balance the interests of both economic development and the environment.

"It's never been the DNR's goal to return the rivers to how they were 3,000 years ago," she said.

The stretch of the Mississippi through the Twin Cities was designated by then-Gov. Al Quie as a "Corridor Critical Area" under an executive order, a type of state regulation that is both problematic and outdated, said Dan Petrik, land-use specialist with the DNR. "The executive order looked at the river as it was 35 years ago," he said. The new rules are being developed to reflect how the river has evolved, and give the state agency stronger and clearer legal authority.

The latest effort revives one that faltered in 2011 after the DNR couldn't reach a consensus with the 21 cities, five counties and four townships in the corridor by a deadline set by the Legislature. A progress report is due to the Legislature in January, and it is hoped the rules will be in place by the end of 2014.

Mississippi issues

The rules drafted in 2011 — covering complex but vital topics such as building height and setbacks from the river bluff — were the starting point for discussion with leaders in each of those 30 communities. Those discussions have been completed, Petrik said. Based on feedback, the rules are being revised.

"In many ways, the Mississippi is more challenging to regulate, because it has so many uses as you move along the corridor," Petrik said. "The St. Croix has more consistent land uses."

The rules, which cover about a quarter-mile from either side of the Mississippi, are attempting to reflect the complexity of those differences, Petrik said. The plan identifies half a dozen distinctive districts in the corridor, divided along urban, rural and commercial/industrial lines.

"They're in a tough spot. They're trying to balance multiple, different interests here," said Minneapolis attorney Troy Gilchrist, who represents Denmark Township, unique in that it is bordered by both rivers. "No matter what they do, somebody's not going to be happy."

Among its concerns, Denmark Township has questioned whether the DNR has the authority to rewrite the rules. In Ravenna Township, near Hastings, and in Grey Cloud Island Township, near Cottage Grove, officials raised concerns that the new rules will create properties that don't conform with zoning rules, making them difficult to sell, alter or refinance.

In St. Paul, nearly 1,000 buildings, and hundreds more yards and gardens, would be affected by proposed "slope protection zones" designed to prevent erosion. "Such over-the-top regulation makes no practical sense and is unjustified," the city's comments say, and there are less intrusive ways of protecting the slopes.

Petrik said those are the types of issues that will be addressed when the new draft of the rules is complete.

St. Croix issues

The course for the St. Croix is not as clear.

Last month, the Lakeland City Council, ignoring a recommendation by its Planning Commission, approved five variances for construction of a new home on a bluff overlooking the St. Croix which, among other things, allowed the home to be taller and closer to the bluff's edge than the rules allow. It was the first such zoning case along the St. Croix River to draw the DNR's objections since a landmark Minnesota Supreme Court case in 2010, also involving Lakeland and an 8,000-square-foot riverside home of broadcasting magnate Rob Hubbard.

From 1972 until the Hubbard case, the DNR operated under the presumption that it had implicit veto power over such variances, Shodeen said. The state Supreme Court said the agency had overreached, and that the Legislature needed to make that authority explicit.

Until that happens, the DNR's only recourse is to challenge variances in the courts. Given the Hubbard decision, and the time, money and effort those cases would consume, the legal bar for a local government has now been lowered. Despite its objections to the zoning, the DNR last week opted against taking the city to court.

In the past, Shodeen said, it was extremely rare for the DNR not to sign off on a local variance.

"It was more of a partnership, it was a collaboration," she said. "What changed, in my opinion, was property rights. The property rights movement has really influenced City Council decisions."

Development pressure has intensified on the St. Croix River over the past decade, and with it more contentious issues over compliance with zoning rules.

"What I'm most worried about is that our standards are becoming so watered down that there are no standards any more," said Shodeen.

Deb Ryun, executive director of the St. Croix River Association, said her advocacy group is likely to push legislation in the upcoming session of the Legislature to give the DNR that explicit authority the court says it lacks.

State Sen. Bev Scalze, DFL-Little Canada, introduced such a bill following the Hubbard decision when she was serving in the House, but it didn't get out of committee. She has not been approached about reviving the bill, but remains concerned about protecting the St. Croix.

Putting the decisions for development along the river in the hands of local leaders invites pressure from developers that might be harder to withstand than a state agency like the DNR, said Scalze, who served 24 years on the Little Canada City Council.

"A local city council can say 'One house, what difference will that make?' But what if everyone said that? Pretty soon we'd look like the Amalfi coast," along the Italian Riviera, said Scalze. "There's a reason for having the Wild and Scenic Rivers Act. If you don't believe in it, you shouldn't have it, and everybody can just do what they want."

Shodeen, who has been with the DNR for 34 years, worries about the river's future.

"How many metro areas are there where you can canoe on a resource like the St. Croix?" Shodeen said. "It's worth protecting. It's worth fighting for."

Jim Anderson • 651-925-5039 Twitter: @StribJAnderson