Water Talk DNR newsletter - December 2014

Water Talk

December 2014

Welcome to the fourth and final issue of 2014. The Water Talk newsletter is published electronically 2-4 times a year, focusing on topics and resources related to floodplain management, shoreland management, and other DNR land use programs: Wild & Scenic Rivers, and the Mississippi River Corridor Critical Area.

Our main target audience is local officials involved with floodplain and shoreland management or mapping, as well as those at the watershed district, regional, state & federal level. Other target audiences include: surveyors, engineers, lenders, insurance agents, realtors, and others involved with properties or projects in floodplain and shoreland. If you did not receive this link directly, you can subscribe at: http://www.dnr.state.mn.us/waters/watermgmt_section/floodplain/index.html

Help us to keep our local official contact list current. If you are the city or county contact for zoning / permits, or the engineering contact, or the emergency manager, and you did not receive the link to this newsletter directly, please forward your contact information and role to ceil.strauss@state.mn.us 

Please let us know what you think of the content and format of this newsletter, which will continue to evolve based on your feedback. Contact Ceil Strauss (see above) with comments or questions.

Predicting and Managing Slope Failure

By Carrie E. Jennings

Minnesota’s wettest recorded month occurred in June, 2014. The amount and intensity of the rainfall created conditions that led to gravitational failure of rock, sediment and vegetation over a broad region. I conducted a preliminary inventory of failures reported in the Twin Cities metropolitan area and along the Minnesota River corridor from Jordan to St. Peter. The goal was to determine the geologic units that failed and what factors might have affected the stress balance on the slopes.    

Most of the failures were located along the steep slopes of the Mississippi and Minnesota river valleys and the incised reaches of their tributaries.  There were three main types of failure: 

  1. rock and sediment fall related to spring discharge (subsurface stormflow);
  2. rotational sediment slides due to saturated conditions, subsurface stormflow and undercutting or incision from overland flow;
  3. and one instance of possible dry sand failure from ravine incision and toe-slope erosion. 

Two failures in the metropolitan area involved the Decorah Shale and overlying units.  A number of different glacial sediment units failed including the New Ulm Formation, Cromwell Formation, and older glacial units.  

Stability of a slope is achieved when the resisting forces of the sediment or rock equal or exceed the driving forces on the slope.  Water can increase the forces acting on a slope by simply loading it. In one case, a perched wetland that had filled to overflowing appeared to create the excess load because it lay above a slope that failed. That failure was also along a roadway so undercutting of the toe was another factor.  

High intensity rainfall events can exceed the capacity of sediment to absorb water. This leads to overland flow and erosion of rills, gullies and ravines, steepening and destabilizing portions of the slope.   

Water can also decrease the strength of sediment by increasing pore-water pressure. This reduces the friction associated with grain-to-grain contact and may result in failure. Where infiltrating water encounters a less permeable horizon, it locally elevates pore-water pressure and creates a plane of failure for a slide. This was likely a factor where the Decorah shale was found in the subsurface. In glacial sediment, the impermeable layers may be minor fine-grained lenses or even zones within a soil horizon.  

road slope failure - June 2014

Removal of lateral support by humans can change the force balance on a slope. Many of the failure areas had recent modifications. They were located:

  1. above roads and trails that cut into the toe slope; 
  2. beneath new housing developments;
  3. in areas where artificial drainage focused discharge.  

The Federal Emergency Management Agency (FEMA) is supporting DNR efforts to identify areas at higher risk of slope failure and the best management practices that may lessen the risk.

The photo above shows Scott County Highway 60 into Blakeley.The highway had been perched on a narrow ridge between two ravines that lead into the the city. There was work going on in the ravine to the north when the mid-June rains hit. Slopes had been cleared of vegetation for the work.The road was undermined so badly that it was not rebuilt. 

Highway 13 slope failure

The photo at right shows another slope failure above Highway 13 in Mendota. 

A report is being prepared that will identify: key features where the risks for landslides are higher, ways to use existing resources (like geologic atlases) to identify areas of higher risk, and some possible best management practices or restrictions communities could use to reduce potential damage from landslides.

Dr. Carrie E. Jennings is Science Reports Lead for the County Geologic Atlas Program, DNR. Carrie worked for the Minnesota Geological Survey, University of Minnesota for 22 years prior to coming to the DNR. She has taught Glacial Geology at the U of M since 1994. She has mapped the surficial geology of about half of the state at a scale of 1:200,000 or better.  She spent 3 years working as a Principal Investigator with the National Center for Earth Surface Dynamics on bluff, ravine and river processes in the Le Sueur River watershed. 

Minnesota Association of Floodplain Managers News

Floodplain managers' conference tour, Duluth

The annual conference of the Minnesota Association of Floodplain Managers was held in Duluth, Minnesota on November 19-21, 2014. The theme of the conference was "It Doesn't Flood Here! Locations not Historically Prone to Flooding." There were approximately 100 attendees. Major topics discussed included, landslides, hydrologic and hydraulic modeling, recovery programs, flood control projects, stream restorations, case studies and mapping. Next year’s conference location was voted on in a survey from the 2013 attendees and will be held in Moorhead on November 18-20, 2015. A call for abstracts will be going out in the Spring.

The conference featured a tour of locations in and near Duluth affected by the 2012 floods, including Mission Creek, at left.


April 2015 - Flood Insurance Surcharges Will Surprise Many

The flood insurance roller coaster continues! There are several updates in flood insurance premiums that will start to be phased in as the Biggert-Waters Reform Act of 2012 (BW12) and the Homeowners Flood Insurance Affordability Act of 2014 (HFIAA) are being implemented. The April 1, 2015 changes include:

  • New surcharges on all policies (of either $25 or $250)
  • Premium increases of up to 25% for non-residential and non-primary residential buildings
  • Premium increases of up to 18% for primary residential buildings
  • Increases in the Reserve Fund Assessments

FEMA has a good summary of the changes in the October 2014 Fact Sheet “How April 2015 Program Changes Will Affect Flood Insurance Premiums”

Surcharges of $25 or $250

Starting April 1, 2015, ALL flood insurance policies will have a surcharge added. Primary residential structures will have a surcharge of $25. Non-primary residential and non-residential structures will have a surcharge of $250.

FEMA does not have good documentation of whether residential structures are primary or non-primary. All residential structures are being treated as non-primary, until documentation is received that shows the structure is a primary residence. Insurance companies sent letters to many of their policy holders over the last few months. Policy holders were notified that the buildings would be classified as non-primary residential unless documentation was submitted to show the house is a primary residence. It is unknown how many of those letters were overlooked or ignored, and how many policy holders will be surprised with a $250 surcharge due to not providing that documentation.

What This Means in Minnesota

It is unknown how many of the residential buildings are primary versus non-primary, and how many are non-residential. However, FEMA provided breakdowns of the building types for the ~3,500 subsidized Minnesota policies that were the most impacted by the first phases of implementing BW12 and HFIAA. (These were buildings with subsidized policies constructed before the first Flood Insurance Rate Maps for their community, i.e., “pre-FIRM” buildings.) As of late 2012, 11% of the subsidized pre-FIRM policies were non-residential buildings and an additional 12% were non-primary residential buildings. Based on those pre-FIRM percentages, we can speculate that about one-quarter of the policies in the state will be charged the $250 surcharge.

The other major consideration in Minnesota is that nearly 60% of the state’s ~12,000 flood insurance policies are for buildings in the low risk zones (B, C and X Zones), and a very high percentage of those are the discounted Preferred Risk Policies (PRPs). These policies are normally purchased voluntarily and not as a condition of a loan. Typical annual PRP premiums range from $200-$460, so a surcharge of $250 will represent a significant increase. Locally and nationally, a large drop in the number of voluntary policies is expected as policy holders see the premium increases.  

Background on Why the Premiums are Changing

In July 2012, the Biggert-Waters Flood Insurance Reform Act of 2012 (BW-12) immediately moved some properties to full actuarial rating. (Full actuarial rating – or full risk rating  means that the premiums are based on how high  or low  the lowest floor elevation is compared to the Base Flood Elevation, i.e., the 1% annual chance flood elevation.) The main types of properties affected by this change were homes that existed prior to a Flood Insurance Rate Map (i.e., “pre-FIRM”), in cases where the home was sold or the owners purchased a new policy after BW-12 was signed on July 6, 2012. The property owner would then be required to get an elevation certificate and pay full actuarial rates. For those who purchased policies right after the bill was signed, these higher rates kicked in when policies started to be renewed after October 1, 2013. BW-12 also started phasing all the other pre-FIRM building rates to full actuarial rates, with the increases set at 25% annually for many classes of structures. 

The Homeowners Flood Insurance Affordability Act (HFIAA) of March 2014 slowed down some of those rate increases by putting a cap of 18% to any rate increases in any given year for most classes of property. The HFIAA also removed the requirement for rates to go immediately to full risk when purchasing a new policy or upon sale. 

County Shoreland Management Innovations

The 85 Minnesota counties with shoreland ordinances are required to complete an annual survey on their shoreland activities in order to receive annual funding from the Shoreland Management Grant program (part of the Natural Resources Block Grant administered by BWSR). Data from the county reports is used to:

  1. Identify activities that are making a difference in shoreland protection and share those activities with other counties.
  2. Track the amount, type, and location of development activity to assess development trends and potential threats to shoreland areas.
  3. Assess how well certain regulatory provisions are protecting shoreland resources and to identify where DNR follow-up and assistance are needed.

Many counties have developed innovative and original approaches to some common shoreland-related challenges, and the DNR learns of these practices through the shoreland grant reports. Below are some of these innovative practices that counties reported in 2013.

Mitigation Practices:  St. Louis and Carlton Counties

St. Louis County has adopted comprehensive lake management plans for some of its lakes. Any landowner on those lakes who applies for a conditional use permit or a variance must implement a number of special mitigation practices. These practices are chosen by the applicant from lists in the lakes’ plans, with each practice assigned a point value reflecting its impact. The point total for all mitigation practices must meet a minimum established for each lake, as well as additional requirements. For example, an applicant on Lake Vermillion must choose and implement mitigation practices totaling at least six points, with at least one point covering stormwater/erosion control measures and one point covering on-site sewage treatment. Currently, four lakes have such plans. See the County’s web site (Article 46 is the zoning/shoreland ordinance).

Carlton County requires property owners requesting a variance from the ordinary high water level (OHWL) of a classified lake or watercourse to complete a Shoreland Mitigation Plan scoresheet to calculate the existing structure’s degree of conformance with the ordinance – that is, does it meet required setbacks? The applicant must complete a revegetation site diagram and commit to engaging in one or more mitigation activities. These activities must include shoreland buffer restoration and/or maintenance. Plans may also include removal of other structures not meeting standard setbacks, removal of impervious surfaces, wetland restoration, stormwater management, establishing aquatic vegetation, restoring ice berms, and stabilizing an eroding shoreline. Carlton County site-verified three shoreline mitigation plans as complete in 2013, with an additional seven scheduled for completion in 2014. See the County’s Zoning and Environmental Services Shoreland web page.

Non-Agricultural Vegetation Management: Beltrami County

Beltrami County shoreland photo

A largely natural shoreline in Beltrami County. Photo by Lindy Ekola.

A few years ago, Beltrami County expanded the Shore Impact Zone in their ordinance from the standard one-half the required setback to encompass the entire setback.  The county also undertook a cooperative initiative with DNR to create two more restrictive lake classifications in their shoreland ordinance – “Special Protection” and “Sensitive Area” Lakes – in response to a number of development proposals on some of the Natural Environment (NE) lakes. The ordinance states:


  • “The Special Protection (SP) management district is established in order to protect shorelands of waters that are particularly vulnerable to pollution; to maintain a minimal density of development, and to maintain high standards of quality for permitted development.
  • The Sensitive Area (SA) management district is established to properly manage areas which may be sensitive to development due to flooding, steep slopes, erosion, limiting soil conditions, the presence of wetlands, or other physical constraints.”

Of the 229 Natural Environment lakes in Beltrami County, 126 were reclassified as “Special Protection” and 81 were reclassified as “Sensitive Area.” These more restrictive lake classifications increase the minimum lot size and lot width while limiting certain land uses, such as campgrounds, golf courses and mining. These restrictions increase the level of protection on lakes with these new classifications.  See the County’s shoreland ordinance for details.

Other Shoreland Activities:  Scott and Koochiching Counties

Scott County completed two large shoreland restoration and improvement projects on Cedar Lake and assisted landowners with numerous cost-share projects under its authority as the Scott Watershed Management Organization. Projects included:

  • 19 water and sediment control basins
  • 7 grassed waterways
  • 3 rock tile inlets
  • 3 native grass plantings
  • 15 filter strips
  • 4 grade stabilizations
  • 3 streambank stabilizations
  • 1 shoreline restoration
  • 4 rain gardens
  • 1 riparian buffer

Koochiching County is engaging in several ongoing projects to restore or enhance the Rat Root River, including river cleanout, bank stabilization, and establishment of riffle sites for walleye spawning enhancement.

Next month, the DNR will be sending out the survey of counties’ 2014 shoreland activities.  We look forward to learning about other shoreland-related innovative practices implemented by Minnesota’s counties through these surveys, and will provide information on such practices in future issues of Water Talk.

Pervious Pavement in Shoreland: When and Where?

pervious pavement - Hawaii

The use of pervious pavement systems has increased in recent years as an effective way to reduce the flow of untreated stormwater into surface waters and to recharge groundwater. While pervious pavement is preferred over traditional pavement in shoreland areas, it is not exempt from the 25% impervious surface limit in city and county shoreland ordinances. These pavement systems can never replace the benefits of native soils and vegetation in shoreland areas, such as erosion prevention, nutrient uptake, and the preservation of fish and wildlife habitat and shoreland aesthetics. Minimizing the amount of hard surfaces in shoreland areas is critical to achieving these statewide goals for shoreland protection.

Using a “credit” system to allow the use of pervious pavement to exceed the 25% impervious surface limit is prohibited in the shoreland district. And in no case should any hard surface be placed in the shore impact zone (SIZ) or bluff impact zone (BIZ) unless needed for water access. Any project that proposes to exceed the impervious surface limit through the use of pervious pavement should be reviewed as a variance. The following conditions are suggested if a community finds such a variance acceptable. These conditions include guidance from the MN Stormwater Manual and DNR field experience:

pervious pavement for parking
  • The slope of the pervious pavement system should be 2% or less
  • There should be a 3 foot distance between the bottom of the pervious system (including its sub base) and bedrock or seasonally saturated soils.
  • The system should be designed to infiltrate the first inch of any storm from the pavement surface.
  • The system should be designed and installed by qualified individuals and not by the property owner.
  • The system should be set back from basements, septic system leach fields, steep slopes and wells.
  • The site should be inspected during construction for compliance
  • Instructions for maintenance, including a maintenance schedule, should be provided to the property owner and zoning administrator or building inspector. Salt and sand should not be applied to pervious pavement systems.

Zoning Challenge

Shoreland District versus Floodplain

The local zoning official has a resident who wants to construct a 2 car garage at the very edge of the mapped 1% annual chance floodplain (100-year floodplain). The homeowner has had a survey done in the area, and finds that the proposed garage location is just past the elevation of the base flood elevation (the 1% annual chance flood elevation). 

The local official’s questions:

  1. Consistent with Minnesota law, the local ordinance requires the lowest floor to be at the Regulatory Flood Protection Elevation, or RFPE. Does that mean the garage floor needs to be elevated to the RFPE if the garage is proposed on land that is above the 1% annual chance flood elevation, but below the RFPE?
  2. The city has a shoreland management ordinance, and the proposed building site is in the shoreland district. Does that make a difference?

(See answer at end of newsletter.)

Red River Valley: Water, Water, Everywhere…and Lots of Places to Store It

The Red River Valley is the site of multiple flood control initiatives because of its unique geographic characteristics. As described in AgWeek, the Red River Valley of the North is a, “25-million-acre watershed spreads across a mosaic of farmlands, grasslands, forests and wetlands. The valley is one of the most productive breadbaskets of the world and home to critical habitat for wildlife and migratory birds, as well as millions of people living in Minnesota, North Dakota, and South Dakota.”[1]

What is unique to the Red River is that its gradient is particularly shallow. While the river is approximately 550 miles long, beginning at the confluence of the Otter Tail and Bois de Sioux Rivers in the City of Breckenridge, flowing northward into Canada and finally ending at Lake Winnipeg, the river drops but 230 feet—less than one foot per mile—over its entire course. As a result, the river lacks the energy to have created a true valley. Rather, at times of high water it simply spreads over the ancient lake bed through which it flows, flooding farms, towns, and cities, often miles from its channel. Since 1950, the Red River has experienced four major floods impacting large portions of the watershed, including the devastating floods of 1997, 2009, and 2011. In addition to major flooding, the river’s lack of energy and northward course also makes it unusually susceptible to localized ice jams.

New Funding Available through Federal Farm Bill for Flood Prevention and Conservation

To help address these longstanding problems, on July 2, 2014, Agriculture Secretary Tom Vilsack announced that through the 2014 Congressional Farm Bill, an additional $50 million in federal funds would become available to help support flood prevention and conservation in the Red River Valley in Minnesota and North Dakota during the next five years. These funds are in addition to the typical funding available to all states.

The additional funds will be available through the Natural Resources Conservation Service’s Environmental Quality Incentives, Conservation Stewardship, and Agricultural Conservation Easements programs. Unlike many earlier flood control efforts nationwide, much of the funding will be used to retain water in-place and to benefit the natural functions of wetlands and other critical habitat, rather than simply hardening channels and diverting water from population centers.  Flood mitigation programs that may be eligible for funding could include:  

  • Compensation to farmers for water retention efforts that reduce flooding on the Red River; 
  • Efforts to improve water and air quality, conserve ground and surface water, reduce soil erosion and sedimentation, improve or create wildlife habitat; and other structural and non-structural solutions.

Where to Store the Water?

In Minnesota, several flood control projects in the Red River Valley are already in development under the auspices of the Red River Retention Authority. The authority was formed in 2010 to pursue water retention projects in the Valley following the record 2009 flood. Its overall goal is to reduce the volume of water reaching the Canadian border by twenty percent during flooding events. As reported in Bakken Today, a “twenty percent reduction in a 1997-level flood would reduce the crest at Fargo-Moorhead by two feet”.[2]

However, this level of reduction would require impounding 1 million acre-feet below the Canadian border, distributed among many projects throughout the basin. A study for the Red River Basin Commission, an intergovernmental advisory group, finds that retention waters could be stored at 96 impoundment sites, covering nearly 560,000 acres across the watershed. However, those sites are generally found on private land, which in the Red River Valley means it is likely to be working farmland. Finding willing property owners and equitable compensation will take money, good will, and as Gary Thompson, a representative of North Dakota water resource districts remarked, “a lot of time and effort,” to get everyone on board.

In many ways, this effort is more of a natural lands and wildlife conservation project than a flood control effort. But as we have learned over the past century of flooding projects, it is often to society’s benefit to work with nature to store and retard floodwaters closer to their source by using the natural functions of wetlands and other areas for water storage rather than only fortifying the built environment downstream. 

Secretary Vilsack noted in his remarks that the program “comes with a great deal of flexibility, and can allow farming practices to continue on land involved in conservation projects when water conditions allow.” It will be a long process, and one that will take many years to complete, but as Vilsack concluded, “projects can be as small as one section of land,” and “we want to get started now.”

Additional technical and financial assistance information about these programs can be found by visiting the NRCS’s website at www.nrcs.usda.gov/GetStarted  or by contacting a local USDA service center.  A local office may be found by visiting the USDA’s Minnesota Service Center Locator at offices.sc.egov.usda.gov/locator/app?agency=nrcs&state=mn.

[1] “Renewing the Commitment to Conservation”, published July 14, 2014. Agweek.com. http://www.agweek.com/event/article/id/23670/. (Accessed September 4, 2014). 

[2] Retention Authority Claims Gradual Progress”, published April 14, 2014. Bakken Today. http://www.bakkentoday.com/event/article/id/36523/publisher_ID/82/. (Accessed September 4, 2014).

FEMA Map Updates

NOTE: Dates shown as "anticipated" have a high probability of being pushed back as issues arise

New Maps Going Effective:

  • Mahnomen County – Effective on April 2, 2015
  • Wilkin County – Effective on May 18, 2015

Letters of Final Determination (Letters sent 6 months before effective dates):

  • Norman County – February 2015 (anticipated)
  • Olmsted County – March 2015 (anticipated)
  • Hennepin County – March 2015 (anticipated)
  • Anoka County – April 2015 (anticipated)
  • Roseau County – May 2015 (anticipated)

90-Day Appeal Periods:

  • Kandiyohi County – 10/17/2014 to 1/14/2015
  • Carver County – January to April 2015 (anticipated)
  • Polk County – January to April 2015 (anticipated)
  • Wright County – February to May 2015 (anticipated)
  • Scott County – February to May 2015 (anticipated)
  • Crow Wing County – February to May 2015 (anticipated)
  • Marshall County – February to May 2015 (anticipated)

Open Houses:  None scheduled

New Preliminary Maps:

  • Wright County (revised) – January 2015 (anticipated)
  • Houston County – January 2015 (anticipated)
  • Chippewa County – January 2015 (anticipated)
  • Yellow Medicine County (revised) – January 2015 (anticipated)
  • Winona County – March 2015 (anticipated)

Zoning Challenge Answers

Answer to Question 1

A local floodplain management ordinance that meets the minimum state floodplain requirements (and where the community does not have a shoreland ordinance) is only enforced in areas that are below the base flood elevation (the 1% annual chance elevation). In this example, a survey shows that the building footprint is above the 1% annual chance flood elevation, so the floodplain management ordinance is not enforced.

Note: IF the building footprint is in the 1% annual chance floodplain (i.e., on land below the flood elevation), the minimum floor elevation must meet the Regulatory Flood Protection Elevation (RFPE), which is the flood elevation plus at least 1 foot of freeboard, plus any stage increase caused by establishing floodway versus flood fringe areas.

Aha! with light bulb

If there is a conflict between the floodplain map and a survey, the actual ground elevations determine whether floodplain zoning requirements apply.

For the purpose of determining whether it is mandatory to purchase of flood insurance, however, the floodplain shown on the FEMA map is still the controlling element, unless the landowner obtains a Letter of Map Amendment (LOMA) from FEMA.

Answer to Question 2

YES, it makes a difference! If the city has a shoreland management ordinance, that ordinance specifies minimum floor elevations. If the 100-year flood elevation has been determined, the low floor needs to meet the RFPE. If the flood elevation has not been determined, the low floor must be 3 feet above the Ordinary High Water (OHW) elevation or the Highest Known Water Level, whichever is higher. In this example, the flood elevation is known, so the garage would need to be elevated to the RFPE. 

Note: Since most local floodplain ordinances allow garages up to 576 square feet to be wet floodproofed, DNR has agreed that it is consistent with the shoreland management requirements for a community to allow the area below the RFPE to be floodproofed rather than elevated on fill, and more floodproofing options can be considered for other types of structures.