Soil Erosion and Drainage Law Compliance Grant 10 Side Inlet and Buffer Inventory... · 2019. 6. 12. · through existing drainage ditch and soil erosion statutes. During the summer

Soil Erosion and Drainage Law Compliance Grant Side Inlet and Buffer Inventory – County Ditch 10

Victor and Stockholm Townships, Wright County, Minnesota

Prepared by:

Wright Soil and Water Conservation District 311 Brighton Ave, Suite C

Buffalo, MN 55313

July, 2017

Side Inlet and Buffer Inventory – County Ditch 10 July 1, 2017

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Table of Contents

Introduction…………………………………………………………………. 3

Methods……………………………………………………………………... 3

Results………………………………………………………………………. 5

Discussion…………………………………………………………………... 6

Conclusion………………………………………………………………….. 8

Appendix A: Site Location, Side Inlet, and Buffer Inventory Maps…… 9

Appendix B: Individual Site Assessments………………………………. 20

Appendix C: CD 10 Wetland Enhancement and Storage Analysis...... 37


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Introduction

In 2015, the Wright Soil and Water Conservation District (Wright SWCD) applied for and received the Soil Erosion and Drainage Law Compliance Grant. This grant is funded by the Minnesota Clean Water Fund and administered by the Minnesota Board of Water and Soil Resources (BWSR) to protect and restore surface water quality through existing drainage ditch and soil erosion statutes. During the summer of 2015 the Wright SWCD used a portion of this grant to inventory and prioritize areas along Joint Ditch 15 (JD 15) that would benefit from side inlet control structures as well as documenting the extent of vegetated buffers adjacent to the ditch. The JD 15 inventory did not exhaust the entirety of grant funds, allowing for a continuation of the inventory to County Ditch 10 (CD 10) during the following summer (2016).

The CD 10 ditch system is approximately 16.7 miles in length and located predominantly in Victor Township, Wright County, within the North Fork Crow River Watershed (Appendix A - Figure 1). The western-most branches of CD 10 drain into Grass Lake (43-0013), a Minnesota Department of Natural Resources (MN DNR)-designated public water. CD 10 outlets into Ann Lake (HUC 07010204, Lake ID 86-0190-00). Ann Lake is a 300+ acre lake, approximately 1 mile south of Howard Lake. Ann Lake is impaired for aquatic recreation due to nutrients/eutrophication (Ann Lake and Lake Emma TMDL, 2011). Ann Lake is connected to Lake Emma (HUC 07010204, Lake ID 86-0188-00) via a small channel. Lake Emma is also impaired for aquatic recreation due to nutrients/eutrophication (Ann Lake and Lake Emma TMDL, 2011).

CD 10 brings nutrients, sediment, and high water volumes into Ann Lake and Lake Emma, which further contributes to their impairments (Ann Lake and Lake Emma TMDL, 2011). Side inlet control structures and buffer strips can reduce the amount of nutrients and sediment as well as slow the flow of water going into these impaired water bodies while also protecting against erosion and fulfilling landowner drainage needs. This report is intended to assist in the prioritization and targeting of areas that could benefit from side inlet control structures and buffer strips along the entire length of CD 10.

In the spring of 2017, the Wright SWCD and Wright County Drainage Authority partnered with ISG to conduct a large scale study of the CD 10 drainage system to identify areas in need of repair as well as BMP opportunities that will benefit both drainage and water quality needs. As of the summer of 2017, ISG has completed a draft of the CD 10 Ditch Repair and Multipurpose Drainage Management Report (CD 10 MDM Report). Although the CD 10 MDM Report is currently in draft form, the storage analysis has been completed and will be included in this inventory as it may assist in the


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targeting of storage areas that will address issues identified in this inventory. Results of the CD 10 MDM Report storage analysis can be found in Appendix C.

Methods

Side Inlet Inventory

ArcGIS software (GIS) and field work were used to identify possible sites for side inlet control structures. GIS was used to determine potential problem areas. Lidar data and aerial photos of CD 10 from 2011 and 2013 and 2015, were used to mark potential areas that could benefit from side inlet control structures. This information was used to better inform a comprehensive field survey along the entirety of the CD 10 system. Photographs were taken at each identified site from different angles, and in most pictures, a four foot stake placed in the eroded area shows relative depth of erosion. A data sheet was filled out for each site, containing information on the date, site number, average depth of erosion (inches), if sedimentation was present (yes or no), the height of the spoil bank (feet), the depth of the ditch at the outlet (feet), the degree of erosion at the outlet (minor, moderate, or severe), depth of ponded water (inches), if there was a vegetated buffer present with an approximate width along the ditch, any additional notes, and photo ID numbers. The ranking of minor, moderate, and severe was determined relatively by comparing the sites to one another. The process of manually walking along the ditch system and identifying sites took about three weeks. The identified sites were entered into a GIS map using coordinates acquired through a Ricoh G700SE camera (which simultaneously captures a photograph and the site GPS coordinates) labeled with their site numbers and categorized by severity (Appendix A – Figure 2).

Buffer Inventory

GIS was used to determine if land adjacent to CD 10 would meet the future required one rod (16.5 foot) buffer of perennial vegetation as outlined in the 2015 MN Buffer Initiative (http://www.dnr.state.mn.us/buffers/index.html). The buffer requirements outlined in this initiative will become mandatory for CD 10 on November 1, 2018. The existing and future required buffers were calculated mainly in GIS based on Lidar and aerial photos from 2011, 2013, and 2015 along with additional knowledge from field observations taken during the side inlet inventory. The future buffer requirement was measured starting from the peak of the ditch spoil bank out 16.5 feet. In areas where no spoil bank was present, the 16.5 feet was measured from the peak of the ditch bank. This “starting point” was manually traced by referencing Lidar and aerial photos. The 16.5 foot buffer area was then generated out from this line. All areas that would not meet the future buffer standard were manually determined and traced. For these areas, the space inside the 16.5 foot buffer area had to show lack of perennial

http://www.dnr.state.mn.us/buffers/index.html


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vegetation. Maps were created showing all areas that would not meet the future buffer requirement along CD 10 (Appendix A - Figures 3 – 10).

Results

Side Inlet Inventory

There were 30 sites that were identified that could benefit from a side inlet control structure. Sites were located on 11 different landowners parcels (2015 Wright County Parcel Data). Of these sites, 12 were recorded as minor, 12 were considered moderate, and 7 were considered severe. An example of each sites severity can be seen in Exhibits 1, 2, and 3 below. The average depth of erosion for minor sites was approximately 13 inches. Average depth of erosion for moderate sites was approximately 22 inches. Average depth of erosion for severe sites was approximately 37 inches. Bear in mind, depth of erosion was not a singular determination on whether a site qualified for minor, moderate, or severe classification, but rather all measurements taken at a site were viewed circumstantially. See Figure 2 in Appendix A for the results of the side inlet control structure inventory.

Exhibit 1. Exhibit 2. Exhibit 3.

Minor erosion at Site 05 Moderate erosion at Site 12. Severe erosion at Site 07.

Buffer Inventory

There are 67 different parcels with property adjacent to CD 10. In total there were 16.9 acres of land currently not in compliance with the coming buffer requirements (see Exhibit 4 below for an example of a ditch segment lacking any type of vegetated buffer). The majority of these lands were being used for agriculture. Along the entire length of


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CD 10, these 16.9 acres constitute 29% of the total 58.58 acres of land adjacent to the ditch that will be requiring the 16.5 foot minimum vegetated buffer by November 1, 2018. The remaining 41.7 acres are either a) already compliant with the 16.5 foot vegetated buffer minimum, or b) exempt from the buffer law. However, on a majority of the land that did have sufficient buffer coverage, the quality of the vegetation present (though compliant) was poor. The vegetative quality of the existing buffers generally consisted of wooded vegetation such as buckthorn and boxelder or herbaceous vegetation such as smooth brome and ragweed. See Figures 3-10 in Appendix A for the results of the buffer inventory.

Exhibit 4. Site 29 where a field adjacent to CD 10 is lacking a perennial buffer.

Discussion

The data collected from this inventory can be used to target and prioritize areas that could benefit from side inlet control structures or vegetated buffer strips. In regards to the 2015 buffer initiative, it also provides a snapshot of the portion of CD 10 in compliance and those areas that are still currently lacking. Addressing just a handful of the issues identified in the inventory could reduce the amount of sediment and nutrients transported downstream significantly. For example, using the BWSR Water Erosion Pollution Reduction Estimator, approximately 20 tons of suspended sediments were contributed to the ditch in one year. Repairing just one severe site could provide a significant sediment load reduction into the ditch. Landowner outreach will be an


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integral component moving forward. Once cooperative landowners have been identified resources can be pooled to fund, design, and implement practices that can address the site-specific resource concerns identified in this inventory.

Side Inlet Implementation

The implementation of side inlets at the inventoried sites will require the utilization of numerous resources. As previously mentioned, landowner outreach will be the most important step given that the implementation of side inlets is not mandatory. Landowner outreach should be prioritized depending on the severity ranking of the sites on their property. Landowners with “severe” sites identified on their property should be contacted first. If cooperative, a feasibility analysis should be conducted by Wright SWCD staff to determine if a side inlet control is suitable for the given site. If deemed suitable, there are multiple sources of funding that can be used to assist in the implementation of the control structure. The Wright SWCD can use State/Local Cost Share or other grant money they currently have to help finance the project. The local ditch authority could also finance projects through the benefited landowners. The Environmental Quality Incentives Program (EQIP) through the Natural Resource Conservation Service (NRCS) can be used by landowners to receive financial and technical assistance. The information from the current inventory can also be used to obtain state or federal grants to assist in funding projects in the future.

Buffer Implementation

The buffer inventory should be used as a coarse resolution “snapshot” of where buffers are likely to be lacking along CD 10 as of the date of this report. This inventory should not be used for regulatory purposes given it is simply an approximation of where buffers are lacking based on aerial imagery and surveyor observation, as opposed to an exact measurement of buffer widths. This inventory is valuable for identifying where buffers are likely lacking so that landowner contact can be accomplished and provides the opportunity to help encourage a proactive approach to buffer implementation. Once contacted, landowners should be presented the data found from the inventory as well as options for financial assistance if they choose to address their buffer deficiencies voluntarily prior to the mandated date of buffer implementation compliance. Prior to this 16.5 foot public drainage system buffer mandate deadline (November 1st, 2018), landowners can utilize various resources to establish vegetated buffers voluntarily. State funding through the Reinvest in Minnesota (RIM) program or federal funding through the Conservation Reserve Program (CRP) are typically the most lucrative options for landowners. Other options for financial and technical assistance can be found in Appendix C.


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Conclusion

The erosion and lack of buffers along CD 10 highlighted by this inventory not only degrade downstream water quality, they degrade the ability of CD 10 to function as intended. The transport of sediment from field to ditch and erosion within the ditch itself decreases the ability of CD 10 to provide adequate drainage to benefited landowners and increases the frequency in which ditch cleaning is required. Despite the fact that the transition from inventorying to implementation is often times difficult in conservation, this inventory will facilitate future efforts to improve the function and sustainability of CD 10, improve downstream water quality, and showcase how government agencies can work with landowners to achieve multiple goals.


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Appendix A

Site Location, Side Inlet, and Buffer Inventory Figures


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Figure 1. The location of CD 10 relative to Howard Lake, Minnesota.


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Figure 2. The location and relative erosion severity rating of the documented sites. These are sites where side inlet control structures may be beneficial.


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Figure 3. Areas lacking the future required vegetative buffer (deadline for implementation 11/01/2018) along the first segment of CD 10.


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Figure 4. Areas lacking the future required vegetative buffer (deadline for implementation 11/01/2018) along the second segment of CD 10.


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Figure 5. Areas lacking the future required vegetative buffer (deadline for implementation 11/01/2018) along the third segment of CD 10.


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Figure 6. Areas lacking the future required vegetative buffer (deadline for implementation 11/01/2018) along the fourth segment of CD 10.


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Figure 7. Areas lacking the future required vegetative buffer (deadline for implementation 11/01/2018) along the fifth segment of CD 10.


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Figure 8. Areas lacking the future required vegetative buffer (deadline for implementation 11/01/2018) along the sixth segment of CD 10.


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Figure 9. Areas lacking the future required vegetative buffer (deadline for implementation 11/01/2018) along the seventh segment of CD 10.


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Figure 10. Areas lacking the future required vegetative buffer (deadline for implementation 11/01/2018) along the eighth segment of CD 10.


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Appendix B

Individual Site Assessments


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Figure 11. Assessment sites 01 and 02.

Assessment Site 01. Assessment Site 02. Minor erosion, no vegetated buffer present. Severe erosion, no vegetated buffer present. Average depth of erosion at 30 inches. Average depth of erosion at 48 inches.


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Figure 12. Assessment sites 03, 04, 05, and 06.

Assessment Site 03. Minor erosion, no vegetated buffer present. Average depth of erosion at 10 inches.


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Assessment Site 04. Moderate erosion, no vegetated buffer present. Average depth of erosion at 36 inches. (At left)

Assessment Site 05. Minor erosion, no vegetated buffer present. Average depth of erosion at 6 inches. (At right)

Assessment Site 06. Moderate erosion, no vegetated buffer present. Average depth of erosion at 24 inches. (At left)


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Figure 13. Site assessments 07, 08, 09, and 10.

Assessment Site 07. Severe erosion, approx. 2.5 feet of vegetated buffer present. Average depth of erosion at 72 inches.


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Assessment Site 08. Moderate erosion, no vegetated buffer present. Average depth of erosion at 36 inches.


Assessment Site 10. Minor erosion, no vegetated buffer present. Evidence of water overwhelming berm into ditch.


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Assessment Site 11. (left) Minor erosion, no vegetated buffer present. Average depth of erosion at 12 inches. Assessment Site 12. (right) Moderate erosion, no vegetated buffer present. Average depth of erosion at 48 inches.


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Assessment Site 13. Minor erosion, no vegetated buffer. Average depth of erosion at 18 inches.


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Figure 16. Assessment sites 15, 16, 17, 18, and 19.

Assessment Site 16. Minor erosion, no vegetated buffer present. Average depth of erosion is 24 inches.

Assessment Site 15. Minor erosion, approx. 3 feet of vegetated buffer present. There is no average depth of erosion.


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Assessment Site 18. Severe erosion, no vegetated buffer present. Average depth of erosion at 36 inches.



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Assessment Site 20. Severe erosion, no vegetated buffer present. Average depth of erosion is 24 inches.

Figure 38. (above) Assessment site 21. Severe erosion, no vegetated buffer present.

Average depth of erosion is 48 inches.


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Assessment Site 22. Severe erosion, 1.5 feet of vegetated buffer present. Average depth of erosion is 24 inches.

Assessment Site 23. Minor erosion, 1.5 feet of vegetated buffer present. Average depth of erosion is 24 inches.


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Figure 18. Assessment sites 24, 25, and 26.

Assessment Site 24. Moderate erosion, approximately 5 feet of vegetated buffer present. Average depth of erosion is 18 inches.


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Assessment Site 25. Moderate erosion, approximately 5 feet of vegetated buffer present.No measured erosion depth at assessment site.

Assessment Site 26. Moderate erosion, no vegetated buffer present. No measured erosion depth at assessment site.


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Assessment Site 27. Moderate erosion, no vegetated buffer present. Average depth of erosion is 6 inches.


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Assessment Site 28. Minor erosion, no vegetated buffer present. Average depth of erosion is 6 inches.

Assessment Site 29. Severe erosion, no vegetated buffer present. Average depth of erosion is 6 inches.

Assessment Site 30. Minor erosion, woody vegetated buffer is present. Topographical low spot where water enters ditch – very minor.


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Appendix C

CD 10 Ditch Repair and MDM Report – Wetland Enhancement and Watershed Storage Priority Analysis

Figure 20. CD 10 Wetland Enhancement and Storage Area Prioritization Analysis.

Documents

Soil Erosion and Drainage Law Compliance Grant 10 Side Inlet and Buffer Inventory... · 2019. 6. 12. · through existing drainage ditch and soil erosion statutes. During the summer