Fall 2017 Water Talk

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Water Talk Newsletter - Fall 2017

October 3, 2017

In This Issue

Water Talk Newsletter is issued three to four times per year.

If you have ideas or requests for the next edition of Water Talk, contact editor Ceil Strauss.

Local Official Scholarships to Attend MnAFPM 2017 Conference - 10/15/2017 Deadline

MnAFPM logo

The Minnesota Association of Floodplain Managers (MnAFPM) is offering scholarships for local officials involved in floodplain management to attend the November 15-17, 2017 conference being held at Breezy Point Resort in Pequot Lakes, MN.

Deadline: October 15, 2017 (revised - pushed back)

More details on the 2017 MnAFPM Scholarship Opportunity for Local Officials

Remarkable Storms: from Myth to Measurement or Can a Houston (TX) Size Flood Happen in Minnesota?

By Pete Boulay, MNDNR State Climatology Office 

In mid-August 1988 I camped with my scout troop on Lac Des Mille Lacs in southern Ontario, Canada. Our site was at the dam that marks the beginning of the Seine River. In the middle of the week, thickening nimbostratus clouds promised foul weather. Rain commenced and did not cease for 48 hours straight. An empty canoe was nearly full of rainwater. The placid river became a torrent and Canadian workers had to arrive via helicopter to remove the stop logs from the dam. We estimated it had to be at least a foot of rain, maybe more.  Nearly 30 years later I found the closest rain gage - about 10 miles away in Upsala - had a two-day total of just 4.84 inches.

120 years earlier, a land surveyor in western Pope County was equally exposed to the elements. Little would be known about the July 18, 1867 storm had George B. Wright not presented his Notes of a Remarkable Storm before the Minnesota Academy of Natural Science on March 7, 1876. Wright stated that he and his crew “… experienced rainfall perhaps without parallel in temperate climates.”

MN Average annual precipitation - state map with inches/year

Wright was curious about the extent of the storm and did his own “bucket survey.” He located “One very intelligent farmer at Westport, Pope Co” who had a large kerosene cask standing on the prairie away from any building was from 2/3 to ¾ full. Wright mentioned that the people of Sauk Center and Osakis claimed with unanimity that rainfall exceeded 30 inches and probably reached 36 inches. There were few rain gages in action at the time in the state and one of the closest was at Fort Ripley in Morrison County that saw 7.50 inches of rainfall. At Ft Ripley the Mississippi River rose eight feet from this storm and caused much damage to log booms and bridges. We may never know what the actual total was from this storm.

In 1978, The National Oceanic and Atmospheric Administration published a paper regarding the Probable Maximum Precipitation (PMP) for areas of the US east of the Rockies and this included Minnesota. The PMP is defined as “the theoretically greatest depth of precipitation for a given duration that is physically possible at a certain time of year.” This is a useful calculation to have for engineers working on large drainage areas. For Todd County this value is around 29 inches in 24 hours. How close has an event reached the PMP? Hard to say in 1867 whether or not these would have approximated the PMP for their areas due to the lack of rain gages. There were just a handful in the state in July 1867.

US Map showing Probably Maximum Precipitation for 24-hour rain
Figure 2. Probable Maximum Precipitation for 24-hour, 10 square mile event. Source: Adapted from NOAA Report No. 51, 1978

By the dawn of the 21st century, there were approximately 1,400 rain gages in use by volunteers in Minnesota, with the bulk of which though the 90 Soil and Water Conservation Districts. Each of these gages has the capacity of about eleven inches. About 175 were with the National Weather Service that used larger gages with the capacity of 23 inches.

August 2007 rainfall map

On August 18-20, 2007 the largest measured rainfall occurred in Minnesota with the volunteer reader one mile south of Hokah in Houston County reporting 15.10 inches. The elderly gentleman needed help lifting the 8-inch diameter gage with so much water in it. The largest non-National Weather Service measurement with a standard 4-inch rain gage with this event was 17.21 inches in 24 hours. The PMP for far south east Minnesota is around 31 inches. The value at Hokah is 49% of the PMP. In comparison, the highest 24 hour total found with Harvey with a National Weather Service gage was 26.03 inches at Port Arthur SE TX AP in Jefferson County. With a PMP in this area of 47.10 inches this was about 55% of the PMP or fairly similar to the percentage at Hokah. The 24-hour total US record remains 43.0 inches at Alvin, Texas on July 25 1979 with Hurricane Charlotte.

The message here is that instrumentation matters. If there are no rain gages, quantification of these events become very difficult. Over the years thousands of unpaid volunteers across Minnesota and the county peer into a rain gage each morning and dutifully report the totals. These observers tend to be quite elderly and new energetic people will need to replace them in the future. Otherwise, we will be back to looking in empty barrels and buckets and coming up with our best guesses. True, there are radar-based precipitation estimates and automated gages, but nothing can replace the quality of a good human observer. A nationwide volunteer program called CoCoRaHS (Community Collaborative Rain Hail and Snow Network) is always looking for new observers. If people continue volunteering there will be quantifiable information on “Remarkable Storms” for years to come.

NFIP Extended to December 8th

The National Flood Insurance Program (NFIP) was set to expire September 30, 2017, but was extended by legislation signed on September 8, 2017.

A wide variety of NFIP reforms has been discussed over the last few years, and those discussions are expected to continue. 

The extension is part of a congressional continuing resolution (H.R. 601) raising the debt limit and funding the U.S. government until Dec. 8. It also authorized a total of $15.25 billion in emergency funding for disaster relief and rebuilding that includes $7.8 billion for Hurricane Harvey victims.

See links to more information about NFIP reform and other topics of interest to floodplain managers at the Association of State Floodplain Managers (ASFPM) site.

Stay out of the Water!

Some people seem to think it is alright to drive through water, or they drove through water before and didn’t have an issue. Some people seem to think their car is a multi-function vehicle and can operate as a boat.

One foot of water can displace 1,500 pounds of weight. That would be enough to float a small car. Two feet of water will carry most vehicles away. Six inches of moving water can sweep a person off of their feet. Water can be deeper than it looks or a road surface under the water could already have been eroded away. The simplest, easiest way to stay safe is to stay out of the water.

Pop Quiz Question: Which picture is a photo of a boat and which one is a truck?

Photo of truck stalled in floodwaters on left & 2 anglers on boat on right

Pop Quiz Answer: Stay out of the water.

Editor's Note:  This article is adapted from the Kansas October 2017 Floodplain Tips newsletter, and is reprinted with permission.

How to Measure Slow Change in the Minnesota River

By Carrie Jennings, PhD, P.G. - Research and Policy Director, Freshwater Society

graph showing Ave Annual Mean Daily Flow is increasing on MN river between 1935 & 2011

Minnesota River flows are increasing from a combination of change in climate, ground cover (evapotranspiration) and altered hydrology. Increased flows mean that rivers have been widening and sediment has been moving throughout the watershed.

River Filling and Dredging

The Lower Minnesota River, from Carver Rapids to the confluence with the Mississippi, is a low-gradient, broad reach of the river. If you wade into the brown water you may be surprised to find that the bottom is actually sandy. Based on the yearly gaging data, about half an inch of sand would accumulate in the channel each year if it were not dredged.

We know that this stretch of the river is meant to slowly fill in, or aggrade over time due to its geologic history, slope and width. However, the rapidity with which the sand is accumulating is affecting ecosystems and more immediately, it is inconvenient and costing taxpayers money.

Barge on Lower Minnesota River

It has the potential to affect commercial barge traffic to the Port of Savage; is using more taxpayer dollars as dredging tries to keep up with the river-filling sand; and will spread sand on a proposed paved bike trail that would run along the levee from the Bloomington Ferry Bridge to Ft. Snelling that DNR contract archeologists were evaluating last summer. Why would flood managers care about this?

Archaeological test pits photo

Archaeological test pits dug along the proposed bike trail route were turning up nothing, which seemed odd to the team contracted to do the work. They finally did hit a couple of layers with artifacts near the natural levee of the river buried by 10 and 20 inches of sand. One layer contained a confusing mess of items that included: a white ceramic pipe stem from Paris that could have dated to the European contact period, some abraded and some sharp pot sherds, some metal, and a small triangular piece of blue plastic. That the layer included metal and plastic means that it dated to the modern time and was redeposited here with older materials, possibly by a large flood event.

Floodplain forest photo

If the half inch of sand that is accumulating in the channel were spread evenly over this part of the river valley, this site could date to the 1960s and the archaeologists would have to dig another 6 to 10 feet to get back 200 years, to the European-contact period. So were they only looking at decades of sediment burying the layers? We don’t know because no one has tried to measure the post-settlement sediment accumulation rate on this portion of the floodplain.

Study Being Done for Lower Minnesota River Watershed District

Dr. Stefanova collecting plants photo

The Lower Minnesota River Watershed District (LMRWD) has engaged Freshwater Society and Lac Core, U of MN to collect and study sediment cores from floodplain lakes that are annually flooded by the Minnesota River and have potential for annual deposition of riverine sediment.  Core analysis will focus on fossil pollen and non-pollen palynomorphs (stomata, algal cenobia, fungal spores and charcoal particles) preserved in the lake sediments that can be used to trace the major landscape changes following the European settlement in the region when the native hardwood forests or prairies have been converted to agricultural fields and ragweed, and other weeds. This will lead to an estimate of changes in accumulation rates of sediment deposited in the overbank setting between Chaska and the Mississippi River. 

In the Future

Ultimately, the LMRWD is interested in facilitating the creation of more upstream water storage to reduce flows and sedimentation, but recognize that they may require more documentation to demonstrate the extent of the impact.

Floodplain managers can extrapolate that with more sediment in the channel and on the floodplain, floodwaters have less accommodation space resulting in higher and more expansive floods.  Sedimentation also reduces the protection afforded by levees.  How much freeboard we are losing and how quickly is an important management question to answer.

Registration Open for MnAFPM Conference - November 15-17, 2017 at Breezy Point Resort

The Minnesota Association of Floodplain Managers will hold its annual conference November 15-16, 2017 at Breezy Point Resort in Pequot Lakes. The CFM exam will be offered at the conference site on November 17th. Registration is now open.

See the MnAFPM web site for more details.

MnAFPM logo

Minnesota Groundwater Tracing Database (MGTD)

The DNR has been working closely with the University of Minnesota to make available decades worth of groundwater tracing information. This information is an important resource for water planning and management in the karst regions of Minnesota.

Dye Tracing

Groundwater tracing using fluorescent dyes has proven to be an effective method for understanding groundwater flow, travel times and interconnections with surface water. Dye tracing involves pouring dye into sinkholes or sinking streams and observing if and where it emerges after flowing through the karst conduit system (usually at a spring or multiple springs). Results have important implications for the protection of trout stream resources and other ecosystems in Minnesota and elsewhere. Additionally, understanding subsurface conduit flow in karst terrain is central to water protection and management associated with spill response, agriculture, water demands, and landscape alteration.

Photo of Bright Green Dye being added to stream

Dye Trace Reporting and Geospatial Data

An expansive list of historic and recent dye trace reports is now available on the DNR Dye Tracing webpage. These summarize results mostly from dye trace studies across the southeastern portion of the state (mostly in Fillmore, Houston, Olmsted, and Winona counties but also sparsely in Dakota, Dodge, Hennepin, Mower, Pine, and Wabasha counties). Geospatial data for these traces is currently available upon request, including dye input points, descriptive information, inferred groundwater flowpaths, and springshed delineations. The data will eventually be incorporated into a web map service available for state and public use. Users will be able to query, select and view the data and associated reports alongside the Minnesota Karst Features Database and the Minnesota Spring Inventory.

The Minnesota Groundwater Tracing Database is an important tool to manage and protect groundwater in Minnesota and making the data more available will add usability to the expansive inventory of karst in Minnesota for generations of scientists and policy makers to come.

Contact Information

Please visit mndnr.gov/groundwatermapping for more information about springs, dye tracing, karst and other DNR County Geologic Atlas Program projects.

Jeff Green, Hydrogeologist, 507-206-2853

 John Barry, Hydrogeologist, 651-259-5660

Photo of karst seepage area

How to Mitigate Development Impacts by Putting the “Condition” in Conditional Use Permits (and Variances)

By Matt Bauman & Jenny Shillcox, MNDNR Land Use Unit

One of the handiest zoning tools a community can use is the “condition.” As local zoning administrators and decision makers, it is important to remember that every development proposal in your community has some sort of an impact – whether it affects views, privacy, shoreland habitat, local hydrology, or water quality – and that communities have the power to mitigate (or reduce or offset) those impacts with conditions. Requiring conditions on permits is common, and every community should be actively using them.

Impacts proportional to conditions

Development proposals requiring a variance or Conditional Use Permit require a greater level of scrutiny due to the special problems that the development may create. These proposals require a public hearing, where potential impacts can be identified and discussed. If findings support granting the variance or CUP, the extent and types of impacts should be considered in developing appropriate conditions to mitigate them. Minnesota law allows communities to impose conditions when granting a variance as long as the conditions are directly related and roughly proportional to the impact created by the variance.

There are some cases where imposing conditions is not a choice, but a requirement. When the variance involves nonconforming lots of record in shorelands, Minnesota law states that communities shall require the property owner to address, when appropriate, storm water runoff management, reducing impervious surfaces, increasing setbacks, restoration of wetlands, vegetative buffers, sewage treatment and water supply capabilities, and other conservation-designed actions.

Vegetative buffer example

Variance conditions serve to ensure that the intent of the regulation being deviated from is met, and to mitigate the impact of the proposed activity. Through thoughtful conditions that can be enforced long-term, the intent of the regulation can often be achieved.

For all conditions, it is important to ensure that they are complied with and enforced long-term. Communities can do this by setting specific timeframes or deadlines for meeting conditions. Communities may also consider requiring the following to help ensure compliance with the conditions:

  • Financial sureties to ensure that the required conditions are completed within specified deadlines,
  •  As‐built drawings and/or photos as proof of completion within the terms of the conditions, and/or
  • Long‐term maintenance and operation agreements for stormwater best management practices and vegetation that must be protected or restored as a condition of approval, along with notices of restrictions recorded against properties to ensure that future property owners are aware of their responsibilities and don’t unknowingly “undo” any conditions.

Impacts versus Conditions nexus graphis 1

The legal basis for conditions has been tested, clarified and supported in many high profile legal cases. For example, Nollan v. California Coastal Commission (1987) made clear that a community must demonstrate a connection (or “nexus”) between a development and the required condition being imposed. For example, if there’s setback encroachment, any conditions attached should focus on the mitigation of that encroachment – whether that be visual screening or a buffer to capture increased runoff. Dolan v. City of Tigard (1994) later clarified how much mitigation is too much. The Dolan decision acknowledged that most impacts are difficult to quantify, and does not have to be shown with mathematical precision. However, the mitigating condition being imposed must be “roughly proportional” to the impact of the development.

Almost all developments create at least one impact. This is a tool communities should be using strategically to benefit their community and protect the resource.

For more information and examples see the DNR web page on Variances in Shoreands, Flooodplains & Other DNR Protected Waterways.  A good place to start is “The Basics: What Communities Need to Know” (six pages) from the Shoreland & Floodplain Variance Guidance Series that was prepared by DNR in collaboration with the League of Minnesota Cities, Association of Minnesota Counties and the Minnesota Council on Environmental Advocacy.  

Who Owns the Bed of the Lake? Is the OHW the Boundary?

Perennial questions about whether the Ordinary High Water (OHW) elevation is a boundary line and who owns the bed of a lake came up at a recent county zoning officials training.

Over 30 years ago, the article Pardon Me Myth! Who Owns the Lake Bed? addressed those same questions in the the Summer 1987 Water Talk issue. (Editor's note: Author Dave Milles was Supervisor of the Waters Permits Unit of the Land Use Section, DNR Division of Waters, at the time of the original article.)

The following excerpts are from Water Laws in Minnesota: Questions and Answers about Minnesota Water Laws (last revised 12/2012).

Who owns the bed of a lake, marsh, or watercourse?

When a waterbasin or watercourse is navigable under the federal test, the State of Minnesota owns the bed below the natural ordinary low water level [see Minnesota Statute 84-032; Lamprey v. State, 52 Minn. 1981, 53 N.W. 1139 (1983) and United States v. Holt State Bank, 270 U.S. 49 (1926)]. The federal test used for navigability is “when they are used, or are susceptible of being used, in their natural and ordinary condition, as highways for commerce, over which trade or travel are or may be conducted.” [See State v. Longyear Holding Co., 224 Minn. 451, 29 N.W. 2d 657 (1947).] If a court has found that a lake is non-navigable and meandered, the shoreland owners own the bed of the lake in severalty. [See Schmidt v. Marschel, 211 Minn. 543, 2d 121 (1942).] If a stream is non-navigable but has been meandered, the shoreland owners own to the thread (centerline) of the stream. If a lake or stream is non-navigable and not meandered, ownership of the bed is as indicated on individual property deeds.

Graphic showing the OHW elevation

What is the ordinary high water level?

The ordinary high water level is an elevation that marks a regulatory boundary of a Public Water lake, wetland, or stream. It is the highest level at which the water has remained long enough to leave its mark upon the landscape.[See Lake Minnetonka Improvement, 56 Minn. 513, 58 N.W. 295 (1894), and Minnesota Statutes, Section 103G.005, subd. 14.] Generally, for basins, it is the point where the natural vegetation changes from predominantly aquatic to predominantly terrestrial. On streams and rivers, it is the top of the bank of the channel.

What is considered trespassing when the public seeks access to a water body?

The belief that the state owns a strip of land around all Minnesota lakes for public use is false. Riparian property (property abutting a lake, river, or wetland) is either privately or publicly owned. The general public can access water bodies or watercourses via public property, but not through private property. Individuals entering private property without permission from the landowner are trespassing and may be prosecuted under the state trespass laws. A person who has legally gained access to a water body may use its entire surface for recreation, such as boating, swimming, or fishing; and any “incidental use” of the bed or bottom, such as anchoring a boat or decoys, wading to fish or swim, and poling a boat, is allowed.

Upcoming Trainings

The following trainings by DNR staff are scheduled:

  • October 25, 2017 (W), 8:45 am - 4 pm - Grand Rapids (DNR offices); County Selected Special Topics (9-12 Floodplain Management Basics;  1-2:30: Interpreting Floodplain Maps or Using FEMA digital data; 2:45-4 Mitigation Grants or Elevation Certificates)
  • October 26, 2017 (Th), 12:30 pm - 7 pm - Thief River Falls (DNR/DOT offices); County Selected Special Topics (1-2:30: Interpreting Floodplain Maps or Using FEMA digital data; 2:45-3:45 Mitigation Grants or Floodplain Culverts; 4-7: Floodplain Management Basics)
  • October 31, 2017 (T), 8:45 am - 4 pm - Cambridge (MN National Guard Armory); Standard Floodplain & Shoreland Training (9-10:15: Floodplain Basics or Higher Standards; 10-25-11:40: FEMA mapping overview & updates or Shoreland Basics & Special Topics; 12:40-1:30 Accessing web-based maps; 1:45-2:50 Interpreting Floodplain Maps or Variances in Shoreland & Floodplain (Shoreland Heavy); 3-4 Floodplain Administration & Permitting Process or LOMCs & Determining BFEs in A-zones)
  • November 2, 2017 (Th), 8:45 am - 4 pm - Blue Earth County Historic Courthouse (Mankato); Special Topics (topics to be chosen about one month in advance) 
  • TBD Winter 2018 - Fergus Falls area
  • TBD Spring/Fall 2018 - There will be County Selected Topics trainings as part of the County Map Modernization effort at many locations.
MN Map with trainging locations

MnDNR will be updating the Floodplain Training and Education page as we get upcoming trainings confirmed.

Contact Ceil Strauss at ceil.strauss@state.mn.us or 651-259-5713 for more details on the topics to be covered at a particular site, or to RSVP for a training.



FEMA Map Status Listing

Actual, scheduled and projected dates since Summer 2017 Water Talk:

Preliminary Maps

  • Polk County (revised) - by end of 2017 (anticipated)
  • Wright County (revised) - by end of 2017 (anticipated)
  • Scott County (revised panels) - Q1 2018 (anticipated)
  • Fillmore County (revised) - Q1 2018 (anticipated)
  • Carver County (revised panels) - Q1 2018 (anticipated)
  • Blue Earth County (revised panels) - Spring 2018 (anticipated)
  • Nicollet County (revised) - Spring 2018 (anticipated)

Letter of Final Determination (LFD)

  • Polk County - Q2 2018 (anticipated)
  • Marshall County - Q2 2018 (anticipated)
  • Wright County - Q2 2018 (anticipated)
  • Houston County - Q2 2018 (anticipated)
  • Scott County - Q3 2018 (anticipated)
  • Carver County - Q3 2018 (anticipated)
  • Fillmore County - Q3 2018 (anticipated)

Effective (6 months after LFD date)

  • Crow Wing County - August 15, 2017
  • Kittson County - September 29, 2017

See latest timetable for past and future map updates and more about FEMA map updates in Minnesota.

    FEMA Fee Waiver for Projects Using Floodplain Culverts

    On August 29, 2017, FEMA issued a letter clarifying that floodplain culvert projects are eligible to have Conditional Letter of Map Revision (CLOMR) and Letter of Map Revision (LOMR) review fees waived. CLOMR and LOMR submittals are required by FEMA and the state for projects located in FEMA Special Flood Hazard Areas (SFHAs) that would affect base flood elevation (BFE) elevations and/or the floodplain or floodway boundary. Fees for CLOMR and LOMR submittals range between $6,500 and $8,250 per submittal.

    This exemption is valid for floodplain culvert projects using the Geomorphic Approach to Infrastructure Design at Road/River Intersections. The project must be a standalone bridge/culvert replacement with minimal other roadwork, or part of an overall ecological restoration project (e.g., stream restoration) where adding the floodplain culverts would further enhance the ecological benefits.

    Photo of bridge with 3 floodplain culverts in the floodplain to the side

    The waiver was granted under Section 22 of the Homeowner Flood Insurance Affordability Act of 2014 (HFIAA), which states that the “requester shall be exempt from submitting a review or processing fee for a request for a flood insurance rate map change based on a habitat restoration project that is funded in whole or in part with Federal or State funds, including dam removal, culvert redesign or installation, or the installation of fish passage.” For the purpose of this exemption, “habitat restoration” will have the same meaning as the term is defined in the Partners for Fish and Wildlife Act, 16 USC 3772 (5).

    To have the fee exemption applied on a specific project, the requester must specify how the project meets one or more of the following:

    1.     Placing floodplain culverts will improve the passage of terrestrial organisms by allowing them to pass under roadways, thus enhancing biological connectivity.

    2.     They will enhance stream stability allowing for more diverse biological communities to colonize and propagate, thus retaining longitudinal connection for aquatic organisms.

    3.     Floodplain culverts will protect the aquatic ecosystem of rivers and riverine wetlands by maintaining the water quality as a result of sediment reduction.  They will allow for a more diverse aquatic community to thrive including the intolerant species that are considered valuable indicators of water quality.

    For more information

    Visit Geomorphic Approach to Infrastructure Design at Road/River Intersections website to learn more about floodplain culverts, as well as floodplain and channel connectivity.  

    If you have questions, contact:

    Kevin Zytkovicz, River Ecology Unit, 651-259-5151

    Salam Murtada, Land Use Section, 651-259-5688