Great Lakes Protection Project

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Demonstration of Drainage Channel Restoration
to Improve Stream Integrity and Maintain Flow Capacity
(Summary of the Proposal Narrative)

Larry Brown, Andy Ward, Department of Food, Agricultural and Biological Engineering
Virginie Bouchard, School of Natural Resources and Ecological Engineering Program
Brent Sohngen, Agricultural Environmental & Development Economics
The Ohio State University, Columbus 43210, Ohio

Peter Richards, Water Quality Laboratory, Heidelberg College, Tiffin, Ohio 44883
Dan Mecklenburg, Soil and Water Conservation Division, Ohio Department of Natural Resources

Introduction

Dramatic advancements have been made in understanding how streams work. The science of fluvial geomorphology is leading a revolution in river engineering and stream restoration. Stream management efforts now focus more clearly on the restoration of ecological integrity and using natural stream characteristics to manage for channel stability and flood control. One application of fluvial geomorphology that remains relatively unexplored is the management of low gradient, artificially drained streams on agricultural landscapes. The overall goal of the project is to demonstrate an alternative drainage channel form that incorporates naturalized fluvial features to enhance stream integrity and maintain or improve drainage capacity. Restoration and monitoring of drainage channels in an agricultural watershed in Northern Ohio, which flows to Lake Erie, will increase understanding and awareness of how we may address multiple objectives while meeting drainage needs.

Environmental Concerns

Highly modified channels drain extensive portions of the U.S. A large percentage of the Great Lakes drainage basin has received drainage improvement for agricultural production. At least 50% of Ohio’s cropland has received drainage improvement, while the north central and northwestern portions of Ohio’s Lake Erie drainage basin are nearly 100% artificially drained. In these highly productive agricultural areas, most natural channels have been deepened and straightened to facilitate flow of water from agricultural subsurface drainage outlets and to maximize conveyance. Habitat modification, largely related to drainage improvement, is now the leading cause of aquatic life use impairment in Ohio. Ecological quality is dependent on fluvial processes that are a function of channel form and associated floodplain interactions. Increased attainment of the Great Lakes water quality standards could be one of the most important outcomes of alternative channel form design and implementation.

Hypothesis: A channelized stream returned to a more natural state will gain improved stream corridor quality, improved riparian zone quality, and improved biological integrity. Specific testable components of our hypothesis are that the restoration of a channelized, low-gradient stream will: 1) reduce flood peaks and increase flow during critical low-flow periods that alter aquatic community composition and lessen chances of survival; 2) decrease suspended solids and fluctuations in dissolved oxygen and ion concentration that impact species survival and community composition; 3) restore pool and riffle habitats; 4) create a greater number of microhabitats, niches and substrate diversities; and 5) reduce substrate embeddedness. We also hypothesize that the restored, low-gradient stream, when properly designed and constructed, will provide the required drainage capacity for agricultural production, subject to land use constraints.

Another potential benefit of returning channelized stream to a more natural state is the possibility of improved sediment management. According to our recent work on Group Drainage Projects (Atherton, 1999), we estimate the cost of drainage ditch maintenance in western Ohio counties averages $450 per mile per year. Over the approximately 3,817 miles of open ditches under county maintenance programs in the western half of Ohio, total maintenance costs exceed $1.7 million per year. Incorporating geomorphic features that improve sediment sorting and transport onto the floodplain, along with continued efforts to implement BMPs on agricultural landscapes, may reduce the need for routine maintenance in modified channel reaches.

A primary product from our proposed project will be demonstration of the engineering technology necessary to achieve the dual goals of drainage and improved ecological quality. A greater understanding of the ecological, hydraulic, sediment transport, and economic implications of two-stage drainage channel forms will be reported. The study will provide information on how to tailor naturalization efforts to local conditions and this methodology will be largely applicable to similar streams under drainage management throughout the Great Lakes Basin, and particularly the Midwest U.S. This information will feed directly into the project’s outreach program associated with Ohio State University Extension. The project team will develop design, implementation, and management guidance materials, make presentations of our efforts and lessons learned at local, regional, national and international meetings, and conduct a regional workshop to extend what we learn to others working in the basin ecosystem.

The project is designed so that our results, and similar studies and demonstrations, could lead to the incorporation of alternative drainage channel technologies into routine efforts of agencies that construct, manage and maintain drainage projects (i.e., county engineers, soil and water conservation districts, municipal drainage districts). The potential is for the naturalization of countless miles of channelized streams in areas of the Great Lakes drainage basin under pressure from nonpoint source pollution, in addition to voluntary and responsible courses of drainage management that meet multiple land use objectives on agricultural landscapes.

This project addresses a very sensitive issue for agricultural producers, county drainage managers and engineers, and natural resources managers in Ohio’s portion of the Lake Erie drainage basin. With the historic tradition of extensive drainage ditch networks in Northwest Ohio, and this region’s documented agricultural productivity, we must begin to develop new drainage management technologies that will help restore Ohio’s portion of the Lake Erie drainage basin to some degree of improved ecological quality (Zucker and Brown, 1998). This project will attract great attention across the state, the Midwestern U.S., and Southern Ontario, primarily because of the huge issue it addresses, “drainage channel restoration.” The project will have great visibility, and therefore, will have a moderately high level of risk associated with it. While we expect to achieve the results stated above and elsewhere in this proposal, the value of this work regardless of degree of success will be invaluable in terms of overcoming the inertia related to the traditional approach to designing and managing drainage ditches.

Objectives

We will demonstrate through applied research and outreach education an alternative drainage channel form approach that incorporates naturalized fluvial features to enhance stream integrity and maintain or improve drainage capacity. This approach is built on sound science and engineering. Specific objectives are:

1. Identify watershed and stream channel sites where the ecological benefits of alternative drainage channel forms can be assessed.

2. Evaluate the ecological benefits of alternative drainage channel forms as measured by aquatic habitat and water quality indicators.

3. Evaluate sediment transport, deposition and sorting in alternative drainage channels.

4. Determine the potential for flood peak attenuation and storm water storage.

5. Conduct an economic cost-benefit analysis related to the design, implementation, construction, and maintenance of two-stage channel forms, water quality, and storm water management.

6. Develop an implementation guide bulletin, and conduct field-days and a workshop to illustrate and teach the design, implementation, construction, maintenance, and drainage capacity and ecological benefits of two-stage channel forms, and prepare the final project report for Phase I.

7. Initiate the process to design and implement a construction demonstration of an actual drainage channel restoration construction project (start of Phase II).

Approach

Phase I of the project will establish the overall approach that can be used for drainage channel restoration construction projects. All information developed from each objective will feed into the work to be conducted on all remaining objectives, and so forth. Phase II will be the initiation of the demonstration and implementation of the approach in an actual drainage channel restoration construction project. Drainage channels in much of the Ohio portion of the Lake Erie Basin, particularly in Northwest Ohio, exhibit characteristics that will allow us to branch our alternative approach into two main groups, 1) focus on channels that have developed a two-stage, sinuous form on their own, and 2) those that are designed, constructed, and maintained as the traditional drainage ditch.

Our drainage channel restoration work will focus on five components of natural channel form. These geomorphic features include: compound channels consisting of a main channel or bankfull channel with proportions (width to depth ratio) and size (approximately 1.5 yr return period) that mimic those formed by fluvial processes, and a second or flood stage of appropriate width (3x bankfull width); sinuosity or plan form of the bankfull channel within the second stage; bed form or riffle pool sequence; vegetation within the second stage or flood prone area; and substrate or channel bed material.

The proposed work includes the use of natural or relatively undisturbed reference reaches as a control (common in channel restoration efforts). However, the restoration of a pre-disturbance drainage network and hydric soil distribution is not feasible given current land uses, and will be avoided as a guide for channel form design. Alternatively, analysis will be done of existing compound sinuous channels found within constructed ditches and supplemented with theoretical geomorphic relationships. The first stage of the project will be to identify streams that have developed a compound sinuous channel within a constructed ditch. The streams will be assessed to determine ranges of geomorphologic parameters. Potential thresholds to be measured include (but are not limited to): drainage area, entrenchment ratio, width/depth ratio, slope, sinuosity, and channel material. The geomorphology of reference streams will serve as a "blueprint" for modification of existing drainage ditches.

Application of Results

The primary target audience includes county engineers, soil and water conservation district drainage technical staff, county commissioners, conservation district board of supervisors, and local, state and federal agencies that have any programmatic responsibility for drainage network evaluation, design, construction, operation, management, and maintenance. Our secondary, but very important, audience includes agricultural producers, drainage contractors, and others that benefit from some aspect of drainage improvements. In addition to what has already been stated about the importance of the work, our target audiences are interested in this work because drainage in Ohio, particularly Northwest Ohio, is of extreme economic importance to the state in many aspects of food production and development (Zucker and Brown, 1998). Also we must learn how to better manage drainage waters to help improve the ecological integrity of our streams while maintaining the economic viability of the land uses benefiting from the traditional improvements in drainage.

Flow regimes are a cumulative product. To the extent that flow regimes are influenced by the drainage network, that influence is cumulative as well. The concept of alternative drainage channel form explored by this project is expected to have valuable local benefits, but its application must be feasibly adapted to a significant percent of any drainage network to restore the Great Lakes benefits. So to restore the flow regime to the greatest possible extent the emphasis will not be on ideal channel form but on achievable channel form that still produces benefits. This is a departure from traditional channel restoration work that has focused on ideal morphology rather than the most feasible application of restoration techniques. Our approach is important to help ensure that the flow regimes we help re-establish are of the highest possible quality within the given constraints of the multiple-use objectives for these drainage channels.