Regulations & Policies

What are floodplains and why are they important?

A floodplain is the area of land adjacent to a stream channel that is inundated with flood waters during high water periods. Floodplains store water from snowmelt and rainstorm runoff as it moves downstream or as it subsides through infiltration or evapotranspiration. Floodplains are only flooded when a stream overflows its banks. In some areas, they may be inundated on a recurring basis.

Floodplains slow the velocity and reduce the power of floods, protecting downstream areas from flooding or erosive stream velocities. Flooding is a natural process that helps replenish the area’s ecosystem if floodplains connected to the stream during floods.

The term “100-year flood” refers to a flood that has a 1% chance of occurring in any given year. It is not a flood that will occur every 100 years.  The 100-year flood is determined by conducting a hydrologic (flow volumes) and hydraulic (stream characteristics) engineering study. The “100-year flood” is the federal standard for flood protection administration.

Who is involved in floodplain management?

The National Flood Insurance Program (NFIP) was created by Congress in 1968 through the National Flood Insurance Act. Dakota County began participating in the NFIP by adopting a Flood Insurance Study (FIS) and Flood Insurance Rate Maps (FIRMs) in 1973 through the adoption of a Floodplain Management Ordinance. Participation in the NFIP is a city-by-city decision, and all major cities within Dakota County participate. Individual cities adopt a floodplain management ordinance based on standards within the NFIP as well those established by the Minnesota Department of Natural Resources (DNR). Dakota County administers its floodplain management program in all 13 unincorporated townships.

Local floodplain management is accomplished through a three-pronged approach:

1. The FIS and FIRMs are created by the Federal Emergency Management Agency (FEMA).
2. The local unit of government adopts the FIS and FIRMs through a local floodplain ordinance which includes prescriptive land use controls to protect the health, safety and welfare of its residents.
3. The NFIP provides federally-backed flood insurance rates for properties that have been built in or near the FEMA-designated floodplain.

Community specific floodplain maps can be viewed through FEMA’s online Map Service Center. For specific floodplain map and administrative requirements, please contact your city government. Specific questions regarding the floodplain maps or ordinance requirements within unincorporated townships should be directed to the Dakota County Environmental Resources Department at 952-891-7000.

What is floodplain alteration?

Floodplain alteration is any change within the floodplain that affects its ability to accommodate large volumes of water by changing the routing or storage of flood waters. Modified floodplains minimize or completely eliminate the natural functions of the floodplain. Examples include a new building, roadway, fill, or other changes in land use.

When do floodplain alteration requirements come into effect?

Any activity that occurs within the floodplain needs to be reviewed and issued a permit to assure that there is no alteration that would impact the floodplain function. If there would be an impact, a plan for proper mitigation of the impact must be filed as part of the permit application before a permit can be issued.

Contact your city for specific floodplain alteration permit requirements. Within the 13 unincorporated townships, contact the Dakota County Environmental Resources Department.

What are the criteria?

• No net decrease in flood storage capacity below the 100-year flood elevation (1% chance flood event).
• Where Base Flood Elevations have been established, all new structures shall be constructed with the low floor consistent with the minimum elevations as specified in State of Minn. R. Ch. 6120 and consistent with Dakota County and Scott County floodplain ordinances.
• Projects involving development, redevelopment, or subdivision of land shall establish flood storage, flowage, and drainage easements over areas below the Base Flood Elevation of any public water, public waters wetland, or wetland.
• Setbacks for floodplain alterations, fill, or underground utilities shall be established and used along watercourses.
  • Where a watercourse has a sinuous flow pattern and a meander belt can be identified, the setback shall be 15 feet from the outer edge of the meander belt.
  • Where a sinuous flow pattern and meander belt are not readily identifiable, the setback shall provide for the potential for restoration and a sinuous flow pattern.
  • Where there are existing encroachments that limit full restoration, the setback shall be 15 feet from the reasonably achievable restoration width for the meander belt.
  • Where full restoration is possible, the setback shall be 15 feet from a meander belt width established along the stream reach that has a width 10 times the bankfull channel width.
  • Where buffers are required, above ground encroachments, alterations, and fill shall be consistent with the prohibited and allowed uses and widths specified in the Buffer Standard.
• Projects that alter floodplain boundaries and increase upstream water levels, are allowed provided:
  • The applicant obtains easements or other documentation that demonstrates and records the consent of owners of any lands affected by the increased water levels.
  • The action is consistent with other portions of these Standards and Local, State, and Federal Regulations.
  • The upstream, riparian, and habitat impacts are analyzed, and no detrimental impacts result or are mitigated.

What does wetland alteration mean?

Wetland alteration is any action that can change the extent or function of a wetland.  Examples of activities that could be wetland alterations include drainage or tiling, filling, excavation, diversion of water to or from the wetland, or changing the types of plants in the wetland.

Wetland alteration and its impacts will be determined by a wetland delineation, which is the process of determining the actual physical boundaries of the wetland by evaluating hydrology (the presence, movement, distribution, and properties of water), vegetation, and soils at the site. Wetland delineation also includes an assessment of the wetland’s functions and how valuable it is.

When do wetland alteration requirements apply?

Whenever there is a proposed activity (such as drainage or excavation) that may affect a wetland.

What are the requirements?

Any wetland alteration must comply with the Minnesota Wetland Conservation Act (WCA) and other applicable State and Federal regulations.

If a wetland alteration is being performed under an exemption or “no loss” determination under the WCA, a proposed excavation in type 1, 2, 6, or 7 wetlands must demonstrate a beneficial purpose. (See below for a definition of these wetland types.) These include habitat or water quality improvement and must minimize loss of wetland function.

A wetland determined to be a high quality wetland (through a state-accepted assessment method) may not be used for stormwater management and treatment unless the use will not adversely affect the function and value of the wetland and alternatives do not exist.

If a wetland is being replaced or mitigated, siting must follow the priority order below:

1. Mitigation on-site
2. Mitigation within the same minor subwatershed as established by the Minnesota Department of Natural Resources
3. Mitigation within the VRWJPO boundary
4. Mitigation within Dakota or Scott County

Transportation projects shall pursue wetland mitigation projects to the extent practical using the criteria above. However, this does not preclude the use of the Minnesota Board of Water & Soil Resources (BWSR) Local Government Road Wetland Replacement Program.

Wetland type definitions

• Type 1 wetlands are either seasonally flooded basins or floodplains. Vegetation varies according to the season and the amount of flooding.
• Type 2 wetlands are wet meadows. The soil is without standing water during most of the growing season, but is saturated below the
• Type 3 wetlands are shallow marshes. The soil is usually waterlogged early in the spring and often covered with six or more inches of water.
• Type 4 wetlands are deep marshes. The soil is usually covered with water during spring and summer— anywhere from six inches to three feet.
• Type 5 wetlands are open water wetlands, including shallow ponds and reservoirs. The water is less than six feet deep and fringed by a border of emergent vegetation.
• Type 6 wetlands are shrub swamps. Soil is usually waterlogged during much of the growing season, and is often covered with as much as six inches of water.
• Type 7 wetlands are wooded swamps. Soil is waterlogged to within a few inches of the surface during the growing season, and can be covered with as much as a foot of water.
• Type 8 wetlands are bogs. Soil is usually waterlogged and has a spongy covering of mosses.

(Definitions excerpt from BWSR publication “Minnesota Wetlands“)

What are buffers and why are they necessary?

In a watershed setting, buffers are bands or strips with permanent vegetation that run adjacent to a stream or wetland.  The purpose of a buffer is to provide a protective barrier or cushion between activities occurring on the upland side of the buffer and the stream or wetland.

Research on riparian (streambank) buffers has shown that appropriately designed buffers protect and improve water quality by intercepting pollutants carried in surface runoff and shallow subsurface water flow.  The riparian zone is an area that is transitional between the land and the water. Although it makes up a small portion of the landscape, it has a critical impact on the water quality in the stream, as well as the number of animal and plant species supported in the landscape.

A healthy and properly buffered riparian zone stabilizes the shoreline or stream bank, provides erosion-control benefits, provides a source of organic matter for aquatic organisms, captures nutrients, reduces flood peak flows, and provides water temperature controls.

Riparian buffers also provide significant habitat benefits, especially for species with a direct relationship to water for food sources or that require either an aquatic or terrestrial environment for certain life stages.

The Vermillion River Watershed Standards define a buffer as an area of natural, minimally maintained, vegetated ground cover abutting or surrounding a watercourse, public waters wetland, or wetland. A property owner is not required to allow public access to a water quality buffer.

How is this different than the “Buffer Law”?

In 2015, the State of Minnesota passed the “Buffer Law” that requires 50-foot buffers on Department of Natural Resources (DNR) Public Waters and 16.5-foot (one rod) buffers on public ditches. The watershed’s buffer standard does not require placement of buffers immediately, but rather only requires them when properties are subdivided for development. Buffer widths in the Standards are generally wider and affect more types of waterways.

How wide do buffers need to be?

Buffers need to be wide enough to provide the required protection for the uses the stream should support and the condition of the water and land nearby.  To be most effective, buffers vary in width to address the specific local conditions. However, that approach is impractical to apply and regulate, and it would be very difficult to set guidelines or policies that would fit all situations; each situation would be unique.

VRWJPO conducted a public input and review process to identify classifications for different water resources. This process determined that local conditions could be addressed by setting buffering requirements that would be general, yet still specific enough to provide the necessary protections.  The result is a set of five stream buffer and four wetland buffer classifications. A map showing the streams and their designated classification can be found on the Vermillion River Watershed website at www.vermillionriverwatershed.org, search “stream classification map.”

Stream classifications:

• conservation corridor – average 150 feet, minimum 100 feet
• aquatic corridor principal connector with trout stream designation – 100 feet, no averaging (as required by the Minnesota Pollution Control Agency’s construction stormwater permit)
• aquatic corridor principal connector – average 100 feet, minimum 65 feet
• aquatic corridor tributary connector – average 50 feet, minimum 35 feet
• water quality corridor – average 30 feet, minimum 20 feet

Wetland classifications:

• exceptional quality – average 50 feet, minimum 30 feet
• high quality – average 40 feet, minimum 30 feet,
• medium quality – average 30 feet, minimum 25 feet
• low quality – average 25 feet, minimum 16.5 feet (one rod)

When are buffers required?

Buffers apply when new lots are created by the subdivision of an existing property.

Are there exceptions?

There are exceptions to the buffer requirements. The primary exceptions are:

• For any lot that existed prior to the development of the watershed rules (March 2007), the buffer requirement does not apply.
• For any lot that is created that remains eligible for Green Acres, Rural Preserves, Agricultural Preserves Program, or similar agricultural or rural preservation program, the buffer requirement does not apply.
• For any wetland area that is filled under an approved Wetland Conservation Act (WCA) replacement plan or a wetland with an applicable WCA exemption, the buffer requirement does not apply.
• The Buffer Standards do not apply to existing outlots that received preliminary plat approval in the two year period preceding March 22, 2007. Buffer standards in effect at the time of LGU approval of a development agreement shall remain in effect throughout the term of the agreement or for a ten year period from the date of approval, whichever is less.
• In areas zoned agricultural with one building per every quarter of a quarter section (40 acres), the buffer requirement does not apply until such time that the zoning changes and higher density building eligibilities exist. This exemption does not allow transfer of building eligibility for purposes of clustering.
  • Note:  Setbacks for structures constructed in agricultural zoned areas should be met to allow for future implementation of the buffer with no impact to structures (i.e. no structural improvements allowed in setback for buffer).

Where does a buffer start?

Most streams in the Vermillion River Watershed would have the buffer measured beginning at the line of the meander belt. The meander belt is a line connecting the outside points on the same side of a meandering stream bank.  Buffers on water quality corridors are measured from the center line of the flow path. Buffers on wetlands begin at the delineated edge of the wetland (the line where hydrology, vegetation, and soils indicate a change between upland and wetland).

What can and cannot be done within a buffer?

Once a buffer is established, certain activities within it are allowed and others are prohibited.

Activities allowed within any buffer include:

• Use and maintenance of a 10-foot-wide unimproved strip through the buffer to access a waterway or wetland.
• Structures that existed when the buffer was created.
• Placement, maintenance, repair or replacement of public roads, utilities, and drainage systems that are required as part of subdivision approval or building permit, so long as adverse impacts to the buffer are avoided or minimized to the extent practical.
• Clearing, grading, and seeding when performed as part of an approved wetland replacement or stream restoration.
• Construction of underground utilities provided the minimum impact alignment is used, the disturbed area is stabilized, and setbacks are met.
• Construction of a multipurpose trail through an area protected by conservation easement or in a dedicated outlot, provided erosion and new impervious surface area is minimized, and maintains an absolute minimum distance of at least fifteen feet as measured from the edge of the trail nearest the water resource to the wetland or public waters wetland edge, the bank of the watercourse, or the meander belt, and averages at least one-half the total VRWJPO identified buffer width.

Activities allowed within portions of the average buffer width that exceed the minimum buffer width include:

• Stormwater management facilities.
• The area of shallow vegetated infiltration and biofiltration facilities, and water quality ponds not to exceed 50 percent of the pond area, adjacent to wetlands and watercourses may be included in buffer averaging provided the facilities do not encroach into the minimum buffer width.

Prohibited activities include: building, storage, paving, routine mowing, burning, plowing, introduction of noxious vegetation, cutting, dredging, filling, mining, dumping, grazing livestock, agricultural production, yard waste disposal, or fertilizer application. However, periodic mowing or burning or the use of fertilizers or pesticides for the purpose of managing or maintaining the native vegetation is allowed with the approval of the local government unit. Noxious weeds may be removed by mechanical means or by spot treatment with herbicides, but broadcast treatment is not acceptable.

What are some examples of buffer requirements?

• An existing 80-acre parcel is farmed, has no buildings, and has two eligible building sites. The owner sells the property, and the new owner wants to split the property into three new lots, one lot of 77 acres and two lots of 1.5 acres each to use the two building eligibilities. The 77-acre piece will still be farmed, but the other two pieces are going to the new owner’s children to build their houses. The buffer requirement would be in effect on the two 1.5-acre lots if the zoning changes from agricultural to residential, and would not be in effect on the 77-acre parcel, as it would remain zoned agricultural.
• A 10-acre parcel is going to be split into eight lots, six lots of one acre each and two two-acre lots. The owner is going to build on one of the two-acre lots but is doing nothing with the other lots. The buffer requirement would be in effect on all of the lots unless located in an area zoned agricultural.
• A parcel of 20 acres was split into 5 lots of 4 acres each about 20 years ago. The owner is going to sell the property. The buffer requirement does not come into effect unless the new owner further subdivides the lots.
• A 60-acre parcel is farmed and is being split into two parcels, one of 40 acres and one of 20 acres. A house, sheds, and bins are going to be built on about an acre of the 20 acre parcel, but the majority of the 60 acres will continue to be farmed. The buffer requirement would not come into effect if the properties continue to be zoned agricultural and/or continue to be enrolled in Green Acres, Rural Preserves, or Agricultural Preserves.

What is stormwater management?

A change in the use or management of a piece of land directly impacts how fast or how much water might be moving off the site during or after a rain. Rainfall that collects and moves off a site is called stormwater.  The impacts can be controlled through an evaluation using specific design conditions (modeled storms) and designing elements to slow, store, treat, or eliminate (infiltrate or evaporate) the stormwater. Stormwater management provides runoff rate and volume control as well as water quality treatment.

When do requirements for stormwater management apply?

Any land-disturbing activity requires some form of stormwater management. Projects require permits from the Minnesota Pollution Control Agency (MPCA) with significant provisions for managing stormwater both during and after construction if greater than 1 acre of land is disturbed. Complex projects generally require the services of qualified engineering and inspection staff for the review, design, and installation oversight required to assure compliance.

What are the criteria?

The VRWJPO Stormwater Management Standards are organized into four categories: Post Construction Water Quality, Runoff Temperature Control, Peak Runoff Rate Control, and Runoff Volume Control. A brief description follows.

Post Construction Water Quality

Post construction runoff discharged from a site must meet water quality standards established by the MPCA. Infiltration/filtration options described under Runoff Volume Control Criteria are the preferred approach to satisfying the water quality treatment in areas that drain to the trout stream where such areas do not first drain to a waterbody with 10 or more acres of open water. Permanent wet ponds may fulfill the water quality requirements in areas tributary to designated trout streams, with specified restrictions. Water quality volumes satisfied using infiltration or filtration technologies (filtration only in Type C and D soils) can count toward the Volume Control requirements. Redevelopment projects are required to incorporate water quality best management practices (BMPs) to the extent practical.

Runoff Temperature Control

Temperature increases that occur due to land use changes that increase runoff from heated surfaces (pavement, parking lots, or flat roofs) can be controlled by establishing buffers (see Buffer Standard), using temperature sensitive BMPs (such as infiltration), designing temperature sensitive wet ponds, and controlling runoff volume increases with the Runoff Volume Control Criteria.

Peak Runoff Rate Control

A hydrograph (graph of the water level or rate of flow as a function of time) method must be used to analyze runoff for design flows and water levels. 2005 land cover conditions will be applied. Peak runoff rate controls will keep flows from a 100-year, 4-day rain event from exceeding existing condition levels. Numerical flow standards must be adopted at intercommunity boundaries (where stormwater flows into a community from an upstream community.

Runoff Volume Control

Development that creates one acre or more of new impervious surface (rooftops, driveways, pavement, and other features that impede the infiltration of rainfall) must include methods to control the increase in runoff volume above 2005 conditions for a 2-year, 24-hour storm event. Local government units (LGUs) may choose to plan necessary management of stormwater volume on a regional scale (large area, multiple planned developments) or calculate the need on a site-by-site basis for individual proposals.

Runoff volume reducing practices built into site design are the preferred method for meeting volume control. These practices should be considered before designing infiltration or filtration facilities. Practices applying the Minnesota Minimal Impact Design Standards (MIDS) are allowed. The applicant must apply for the credit and provide calculations showing the practice meets the standard.

Specific design requirements for infiltration facilities shall be calculated using appropriate site information and applying design criteria from the Minnesota Stormwater Manual. The function of infiltration facilities is dependent on the ability of soils and underlying materials to allow water to move into the ground (permeability). Constructed infiltration facilities, such as basins and trenches, have several additional requirements.

All stormwater management structures and facilities must be maintained to ensure that they function as originally designed. The responsibility for maintenance is assumed by the LGU with jurisdiction over the facilities or by the applicant in a compliance agreement with the LGU.

Are there exceptions?

Some exceptions may apply and criteria may be waived if an LGU can meet requirements set forth in the standards.

Local City/Township Controls

Local ordinances of LGUs may require permits for smaller land disturbing activities and may have stricter controls. Local ordinances may also have specific rate and volume control requirements for redevelopment projects (not solely projects that create new impervious surfaces).

What does drainage alteration mean?

Drainage alteration refers to a change in the natural course of water flow as it moves through the watershed.  Drainage alteration may take the form of creating artificial drainage, pumping, diverting, obstructing (impounding or damming), channeling, or otherwise modifying the natural process of water movement through the landscape.

If drainage alteration is proposed, a permit must be obtained from the Local Government Unit (LGU) or the Vermillion River Watershed Joint Powers Organization (VRWJPO). The proposed drainage alteration is required to meet the criteria in the drainage alteration standard set by the VRWJPO.

When do requirements about drainage alteration apply?

Drainage alteration requirements apply when:

1. An outlet is being proposed for a landlocked basin with a contributing area of 100 acres or more; or
2. A drainage alteration is being proposed for a watercourse, public water, public water wetland, or wetlands that drain 640 acres or more.

What are the criteria in the standard?

For draining landlocked basins:

1. Outlets are consistent with other portions of the VRWJPO Standards, as well as other local, state, and federal regulations.
2. Analysis is completed of potential downstream, riparian, and habitat impacts of outlets; implementation results in no detrimental impact to property or natural resources.
3. Runoff analysis for flows and water levels are based on a hydrograph method. A hydrograph is a graph showing changes in water flow or water level over time.
4. The proposed post-installation hydrology (water distribution and movement) is consistent with peak runoff rate and volume controls.
5. The outlet does not create adverse downstream flooding or water quality conditions, or affect stability of downstream water courses.
6. The outlet maintains dead water storage, a volume with little to no current, in a basin or channel to the extent possible.
7. Low floor elevations of structures are appropriately set back (consistent with Floodplain Alteration Standards).
8. Development contributing runoff to a landlocked basin incorporates best management practices to reduce the runoff volume to the extent possible.

For proposed alteration of waterways, public waters, public waters wetlands, or wetlands:

1. Alterations or diversions are consistent with other portions of the VRWJPO Standards, as well as other local, state, and federal regulations.
2. Analysis of potential downstream, riparian, or habitat impacts of alterations or diversions are completed and predict no detrimental impacts.
3. The proposal demonstrates a reasonable necessity for the alteration or diversion to improve or protect public health and safety or to improve or protect aquatic resources.
4. Unnecessary injury to upstream or downstream lands is avoided.
5. The alteration provides greater benefit (positive impacts of drainage, dam or diversion) than harm (costs) to lands affected by the alteration.
6. The alteration benefits the natural hydrologic system by returning, restoring, or maintaining its natural capacities.

All drainage alteration proposals must provide for stable channels and outfalls that will not erode stream banks or shorelines.

Are there exceptions?

The LGU or VRWJPO may waive the evaluation of impacts if:

1. The landowner can demonstrate that the proposed drainage alteration will cause no off-site impacts (erosion, sedimentation, flooding, or other damage); or
2. The landowner provides proof of the consent of potentially impacted landowners through easements or other documentation (in a form acceptable to the LGU or VRWJPO).