Professional Landscaping - Wetland Restoration

Create a Water-holding Structure with Good Circulation

Bioretention ponds are similar to bogs.  They can hold deep, standing water, so safety is a key issue. Common problems with retention basins is that they can be undersized, constructed incorrectly, or do not drain properly, resulting in over- flows. Slight over design is a small cost compared to basin failure. Once constructed, bioretention ponds can be planted with bog-type plants, ranging from those that tolerate constant standing water, to those that can handle dry soils.

Always make sure your soils percolate and, if needed, use an under-drain. Retention basins will have spillways with overflow drains and piping sized to handle the flow. You need to provide details for your basin, with existing and proposed contours. A lot of designers would like to do one big bio-retention area, but a treatment trains work a lot better. Try to work in grassy swales and level spreaders to slow water and to remove sediments before they reach the basin.  Slow the flow of water and clean as you go.

Fourteen Challenges for Mitigation Planting Plans

I worked with and reviewed over eighty different stream restoration projects as the landscape architect for a state transportation department. Some of the common roadside stream restoration struggles were:

Enforcement Guidelines

As a designer, the best way to avoid communication issues in restoration planting projects is to provide simple, clear instructions for the field inspection engineer. The best-laid-plans are useless if no one is monitoring installation, and this step in the restoration project process is sometimes the weak link. The inspector might be part of your internal staff, but for larger projects, it could be an area division office within a large agency or an inexperienced subcontractor foreman. The way to maintain quality control is to provide as much help as possible without crossing boundaries of contract protocol—a delicate balancing maneuver!

First, introduce yourself to the field inspection engineer by phone, or better yet, in a face-to-face meeting. There is nothing online that can replace a friendly hand shake. Let them know you are available to answer questions and provide technical expertise, especially during conflicts with the contractor. Supply them with a plain-language explanation of the contract specifications, pointing out general issues they may encounter, and tell them special things to note. Provide references to the specification numbering for your instructions. The important thing is to not rewrite the specs!

Instead, reinforce the written specifications and plan sheets as the governing documents by explaining why certain sections in the specs exist, without restating the contract requirements in your own words. Assume the inspector is not familiar with horticulture. For example, the specs may require the contractor to install bare root seedlings that remain viable for a minimum of two years. Your inspection instructions may explain that bare root seedlings have root systems that will dry out and die if exposed to open air longer than fifteen minutes. Since the time of planting is during the dormant season when the seedlings have no leaves, making sure the roots appear moist is especially important. It is also important to look for the first new leaves sprouting the following spring. If the inspector doesn’t see any green by June, the plants are not viable. This is obvious to an experienced wetland restoration expert, but may be a revelation to the field inspection engineer.

Now That the Plants Are In, Maintain to Sustain

Following through with upkeep after a restoration landscape is installed easy to overlook. It takes just a few months for a typical, large-scale landscape planting plan to deteriorate without adequate maintenance. Luckily, a vegetative mitigation planting for a disturbed stream buffer is not the same as an ornamental landscape. It requires a less-intensive maintenance approach.

Start with a site where invasive plants have been eradicated before planting. It is best to remove exotic pest plants in adjacent areas, too. Then go with a reliable, self-sustainable landscape design that requires minimal care once the plants are in the ground. Cover the ground with natives—grasses, herbaceous forbs, and seedlings to get the upper hand on the non-native competition. A good design and proper installation can save you lots of trouble later. Understanding natural plant succession can ease long-term maintenance by creating a stream buffer site that grows spontaneously into a typical, unmanaged woods.

A multitrophic stream buffer planting starts small. The ground surface starts as an inexpensive seed mix and the tree and shrub seedlings are usually only three feet tall. These items act as placeholders for the eventual volunteer growth that makes up a mature woodland buffer. They need to grow vigorously and remain healthy until the real buffer vegetation fills the site. Do the following two things to provide the best chance of success: 1. Seed with a mix of quick-cover native grasses and herbaceous forbs adapted to both cool and warm-season germination to stabilize the disturbed soil. 2. Plant bare root seedlings rather than container plant material during the dormant season to ensure immediate, full root contact with moist soils.

That’s not enough to guarantee a thriving wetland, though.

My job at a state Department of Transportation was to review landscape plans, provide technical advice for anything related to landscapes, write contract specifications for planting and grassing, write maintenance specifications and work plans, and create statewide policies for roadside projects and permits. The Department had about 4500-personnel statewide, including many civil engineers and ecologists as well as external consultant designers. I reviewed about three hundred projects a year.

I was also on the state Soil and Water Conservation Commission’s technical advisory committee for several years, working on changes to the GREEN BOOK—the erosion control manual for the state. Several new stream and wetland laws were in their infancy during this time.

My background is in landscape architecture with a strong emphasis on horticulture. I did a lot of industrial campus plans and municipal work before coming to the Department, and I worked, early in my career, on large-scale planting and irrigation plans. I did some residential work, too. I got to know the green industry and gained practical experience in how to keep plants alive and maintain them. You get to know plant species after specifying several hundred of them on a single site!

During my time at the DOT I reviewed over eighty riparian mitigation projects. My review process evolved with each experience. Our section, Maintenance, was called into roadside restoration work initially during a crisis. There were active consent orders on nineteen stream disturbance violations in north, south, and central Georgia—just as budgets had been slashed and all the environmental consultant contracts were closed. Our section was asked to write the specs, rework the plans, procure the plant material, train the asphalt/pothole crews, layout the sites, accept the plant material, supervise the installation crews, monitor the results, and write the maintenance instructions for the restoration planting—all within about a month and a half—all nineteen sites. A lot of things had gone wrong, and we were asked to come in and fix them quickly.

We learned a lot in the process. We rewrote our standard planting specifications. We learned how important is was to connect with the district and area field inspection engineers and provided plain-language instruction to help in monitor contract installation and maintenance requirements.

The department-wide plan development process was eventually adapted to include landscape architectural review of mitigation proposals early in the design phase. A single project manager was assigned to each road project. The Environmental Services division amended their protocol to include the landscape architecture section’s input and review of landscape mitigation plans. Later, I provided internal and external training classes based on common issues encountered in the plan reviews. As a result, our new stream relocation and disturbed buffer restoration process helped expedite road projects and save a lot of money. The consent orders were lifted and we didn’t have any new EPD violations.

What do I want to tell you about restoration planting?

It’s simple to do a restoration/planting/mitigation plan for roadside stream relocation projects. All you do is seed a native riparian seed mix over the disturbed area and then, during the dormant season, plant native bare root seedlings eight feet on center. This is the least expensive, most self-sustaining way to establish a welcome mat for natural succession.

The devil is in the details, though!

I want to share as much as I can with you about what I learned, but you can find more detailed information in my Advanced Guide to Environmental Mitigation eBook. I would love to hear your comments and about your restoration stories and experiences, too. 

ASWM

Is your specialty wetland restoration? The Association of State Wetland Managers has a great series of webinars on improving wetland restoration success. 

The Role of Landscape Architects

Success and failure—good restoration projects are nurtured by both. Experienced mitigation experts are born during the in-the-field challenges of vegetative restoration. Not all of these experts are landscape architects, but eco-restoration teams for projects large and small, benefit from a landscape architect’s perspective and participation. There are many different factors that contribute to a stable, dynamic equilibrium for stream channel sediment, and well-established native vegetation on the stream buffers is an essential part of that stability.

The professions that provide bioengineering expertise have become highly specialized, but still need to incorporate good horticulture, landscape design, engineering, and maintenance knowledge into a workable, sustainable landscape restoration plan. They need an experienced vegetative mitigation landscape designer on board. If you are new to this category of work, it pays to consult with seasoned professionals and get reviews and comments from them during the planning and design-drawing phases of the project. You need narrowly-focused professionals and designers as well as those who think about the big picture and field-experienced planners to make your eco-restoration team complete.

Nationally Known Plant Experts

One of my great pleasures was to participate in a three-day intensive course taught by Dr. Robert Mohlenbrock on wetland plant identification. He was over seventy at the time, but he out-hiked and out-talked everyone else in the group. We discussed and saw about three hundred plants, growing in natural wetland habitats. Dr. Mohlenbrock, or “Dr. Mohley” as some referred to him, could pontificate about the tiniest differences between spikelets in Juncus or the significance of smooth or hairy stems in identifying Rhexia species, without any hesitation or lack of surety. He was a walking encyclopedia. We were all fortunate to be in the presence of a true wetland identification superstar.

The same feeling was evoked when I took a two-day seminar on native azaleas taught by Fred Galle, also over seventy at the time, the preeminent expert on azaleas and hollies. He was responsible for the garden design and maintenance of Callaway Gardens in the early years when horticulture was a strong focus of the leadership there. The information he provided on the care and maintenance of azaleas was golden! All these people provided me with more facts than I could ever use, and the experience of walking through marshes and forests with them was amazing and delightful.

The main lesson for me was how important experience is to success when dealing with vegetation and landscape design. There is no substitute for the tried and tested methods by people who are passionate about plants. Each expert mentioned something every few minutes I had never read in any book or publication—and never will.