2 Stage Ditch. Improving the function of Agriculture drainage ditches

Transcription

1 2 Stage Ditch Improving the function of Agriculture drainage ditches

2 2 Stage Ditch Designs

3 HYDROLOGY in our Environment 1. Hydrology and hydro-modification 2. Stream Channels and natural channel evolution 3. 2-Stage Ditches A design to help protect streams and improve water quality

4 Presentation Objective Understand the importance and gain an appreciation for why a ditch must be considered as part of a larger system that includes a connection to the adjacent area and the watershed as a whole.

5 Overall Goal Understanding how constructed channels seek their own stability will allow us to manage and construct ditches that in the long-term might require less maintenance, provide drainage conveyance, reduce sediment export, and better provide an ecological function.

6 Key Concepts Stable natural streams typically consist of a main channel with a particular width-depth ratio, and a floodplain connection. Stable channels just convey the effective (bankfull) discharge and larger flows widen out onto the floodplain. Bankfull discharge is the discharge which shapes and maintains the channel. In agricultural ditches where flows from subsurface drainage systems dominate, the bankfull discharge occurs more often with increased moisture levels.

7 Results of Altered Hydrology With changes in hydrology from filling in wetlands, removing trees, increasing the amount of tile drainage, increasing development, placing more impervious surfaces on the soil we have bypassed our natural filters placing more water more quickly into the systems that once were able to handle the loads they were receiving.

8 Design makes ditch banks and sides slopes more stable than a conventional U or V shaped ditch. Why 2-Stage Ditches? Use existing infrastructure ½ mile of 2 Stage Ditch removes approximately 105,000 pounds of sediment each year Removes Nitrogen and Phosphorus Allows for greater water holding capacity in the ditch

9 Before and After Shots of a 2-Stage Ditch Ditch Prior to 2-Stage Construction Ditch After 2-Stage Construction

10 2-Stage Ditch allows added storage capacity to keep water inside the ditch banks and out of the adjacent farm fields.

11 2-Stage Ditch Benefits 1. Reduced maintenance activity on that section of drain Reduced sedimentation and nutrient movement from construction and maintenance activities 2. Nutrient and sediment removal Deposition on and removal by the Floodplain benches 3. Increased capacity of the ditch system and floodwater retention 4. Helps to mitigate downstream flooding If applied at appropriate scale within a watershed 5. Improves ditch bank stability and reduces bank sloughing 6. Improved in-stream habitat

12 Biology Begins the Healing Process % Isopods in stream samples in both sections Control section Study Section Pre construction Post construction Isopods are aquatic crustaceans that are tolerant to water quality degradation Lower % of isopods in the samples leaves room for additional, more tolerant species to make a comeback Decrease in Isopods indicates water quality and habitat improvement and overall biological improvement.

13 More Biological Data Number of Sunfish Species Found in Samples Control section Study Section Pre-Construction Post - Construction Sunfish are indicative of good water quality and habitat Increase in sunfish species directly after construction of the 2-stage suggests that the water quality and habitat improvements are a result of the 2-stage construction

14 Isopod % in Macroinvertebrate Studies

15 Number of Sunfish Species Present

16 Nitrogen Management Total reach N removal increases with 2 Stage Construction % of N removal is the most when loads are the lowest most effective when coupled with other strategies such as nutrient management Total N Removal (g N/day) Sand Removal FBOM Removal Bench Removal Sep 06 Nov 06 Feb 07 Apr 07 Jun 07 Aug 07 Oct 07 Dec 07 Date Feb 08 Apr 08 Jun 08 Aug 08 Oct 08 Dec 08

17 Nitrogen Removal Area (m 2 ) Mean N-Removal (g d -1 ) Before After Before After Stream 1,502 1,502 1,931 1,931 Benches 756 3,780 1,870 9,360

18 Sediment Removal Potential Recent Studies show the removal of 53 tons of Sediment on an annual basis as a result of installation of a half mile of 2-stage ditch Reliability Longevity Maintenance savings Uses existing infrastructure

19 Channel Evolution

20 The INS and the OUTS 1. More drainage benefit with moderate topography, too much or too little not as conducive for 2 Stage 2. Too fast of gradient in stream may erode and make less stable, too slow of gradient and the 2 Stage may act more like a wetland 3. Select a project based on NEED erosion, sedimentation issues, or drainage concern; and not mere perception 4. Look for ditches that show signs of natural bench formation, if the ditch is stable leave it alone!!

21 Design and Engineering Site selection less than 4 tenths slope Conduct survey cross sections of ditch every 100ft noting features and tiles Gage station data and landuse information Import into program/engineer the design Implement the design

22 Design Resource er/water/streammorphology/default/ta bid/9188/default.aspx

23 When is a good time to construct these sites? It is essential to construct 2 Stage Ditch sites with the following criteria in mind Is a cover crop or other vegetation going to be able to establish quickly on the side slope and benches that are newly constructed What is the soil moisture, is it wet or dry conditions the drier the better Try to avoid times of year that have excessive moisture levels the spring rains and the late fall and winter cold temperatures with threats of both rain and snow Spreading spoil in many cases can be done in the adjacent farm fields planted crops will pose an issue, timing is important if there is corn or beans present, if you are able to plan ahead possibly a wheat crop in the area adjacent to the ditch would give the ability to construct during the growing season.

24 What it takes to make a project happen Secure a funding source IDEM 319 Grant Community Foundation Dollars LARE funding Mitigation dollars SWCD or RC&D EQIP program (cost share funding) Private funding in coordination with drainage maintenance fund Sit down and discuss project with County Surveyor and NRCS District Conservationist. Find willing landowners and project location Survey the ditch and develop a design Secure necessary permits through DNR, IDEM, US Army Corps. Implement the project

25 2-Stage Ditches A recipe for Success Figure out the right ditch to work on Showing signs of instability or flashy stream hydrology Headwater streams with little or no woody vegetation Determine flooding frequency for your benches A function of overall ditch hydrology and bench elevation Involve Critical Stakeholders from the beginning County Surveyor / Drainage Board Decision-Makers NRCS / SWCD / Engineers Technical Help Landowners Decision Makers

26 Funding needs Most 2-Stage Ditch projects will cost around $10/linear foot Funding Drainage Board, Grants, Lake and River Enhancement, Private sources, State and Federal cost share programs Additional expenses 1. Seed for benches and side slopes 2. Erosion control blanket 3. Trucking expense for soil, if it has to be moved off site 4. Fixing of tile outlets 5. Excessively deep ditches and banks All of this increases the expense of construction

27 Local Support Coordinate with Surveyors and Drainage Boards, collaborate with them on a drain that represents a need and is a problem drain for them due to bank slumping and instability which poses a regular maintenance issue for the county. Work with NRCS District Conservationist (DC) on coordinating designs and surveying, they will also be key on directing you to landowners that may be interested and save you time.

28 Find the Landowners Topics to discuss 1. Loss of soil is loss of production for them 2. 2-stage will be able to hold more water which results in less ponding in their fields 3. Increased capacity allows better drainage from tiles 4. Increased stability of the ditch which can result in a decrease in their maintenance payment if the county would decide to do so.

29 Permitting Talk to individuals from Army Corps about the project from the start, then send them results of the survey and detailed information on when you would like construction take place, where at, and specifics about the project including cross section data and soils information Discuss project with IDEM, you may need a permit through them, IDEM, or DNR

30 Common Scene

31 Good sites for a 2-Stage Ditch

32 Sites where a 2-Stage Ditch is not the right choice No added capacity for benches Expensive deep ditch lots of soil to move One side construction possible Too much woody vegetation

33 Is a 2-Stage Ditch what you need? Is this ditch a frequent problem requiring maintenance and clean-out Is there bank slumping occurring Does the drain need more water holding capacity, is there flooding downstream, high velocities during rains, excessive bank scouring Are there moderate/normal flows in the ditch Is there little or no woody vegetation present If you answerer yes to the majority of these questions, a 2-Stage Ditch may be the tool avoid/control/trap nutrients/sediments

34 Ditches as a part of a larger system Land-based conservation activities are still important Wetlands and ponding areas strategically placed in a watershed can help alleviate high flows Land-based erosion and sediment control measures and nutrient management strategies are still necessary

35 Closing Thoughts When managed for water quality, headwater streams and ditches have tremendous potential to improve downstream health of rivers. Many times ditches do not need maintenance performed but are viewed as functioning poorly because they look bad. As stream (ditch) habitat improves, fish and invertebrate communities improve.

36 Closing Thoughts (continued) Not every mile of every ditch needs to be constructed into a 2-stage channel. Strategically selected sections scattered throughout a watershed will make a difference in stream flows and velocities and enhance channel stability The goal is to install 2-stage ditches at a sufficient scale within a watershed to make a difference in flows, sediment movement, nutrient removal, and to achieve other desired environmental benefits

37 2-Stage Ditches in Indiana

38 The 2-stage ditch is the perfect marriage of a long-lasting, sensible conservation strategy with the need for drainage to support agricultural production 2-Stage Ditches and Agriculture

39 Questions or Concerns Contact The Nature Conservancy at or Contact your local NRCS District Conservationist or local Soil and Water District office Contact your County Surveyor