WETLAND RESTORATION

 

I. RESTORATION PRINCIPLES

A. CHOOSE FORMER WETLAND THAT IS DEGRADED

Do not choose an upland system that is functioning comparatively well and convert it to  a wetland system that may not achieve successful functioning for decades.

B. SITE, IN CURRENT CONDITION, SHOULD BE OF LIMITED VALUE

C. PRESERVATION IS A BETTER OPTION FOR SOME WETLANDS

D. USE REFERENCE WETLANDS

II. SITE ASSESSMENT

A. DISTURBANCES

Causes of initial degradation may still be around: sediment, invasives, changed hydrology

Look for disturbances in the wetland (fill, non-native soil)

Look for off-site disturbances:

          Construction upstream

          Changed watershed

          Changes in other wetlands upstream

          Diminished buffer

          Nutrients in stream

Invasives: Why are they there? (continued disturbance, historical disturbance, canopy removal)

Toxic fill: wetlands have historically been filled

Grazers, tramplers, hiking trails, buffer clearing, buffer dumping

B. HYDROLOGY

Is the hydrology still there, is it really a wetland?

Max-min water levels, frequency of fluctuation, how long floods?

Water depth

Flood energy

Dry periods?

C. WATER QUALITY

Sediment

Nutrients (esp. for bogs)

pH (esp. for bogs)

Urban runoff:  oil and grease, metals, solvents (plants might survive, but would you want to attract animals to such a habitat?)

Excessive waste flow (hobby farms, septic systems, dairies)

          Nutrients, pathogens, OM

D. TOPOGRAPHY AND SOILS

Bathymetry is critical:  you need to know the contours to less than 6” in shallows (where you plant)

Soils: will the wetland hold water?


E. ECOLOGICAL COMMUNITIES

Existing plant stock

Reference site

Exotics

Potential donor sites

          Active

          Passive

Potentially damaging or undesirable animals

          Vegetation: livestock, deer, elk, beaver, muskrat, nutria, geese

          Wildlife: bullfrogs, starlings, carp, rats, domestic and feral dogs          and cats

F. WETLAND FUNCTIONS

 

III. PRELIMINARY RESTORATION DESIGN

          Hydrology, spatial relationships, substrate:

A. HYDROLOGY

1. VOLUMES AND FLOW

To get enough water: dig deeper, impound it, pipe it in.

2. IMPOUNDMENT

Levees, dikes, sills, sumps, etc.

3. CONVEYANCE

To avoid flood damage pipe it around wetland (“tightline” it)

 

B. TOPOGRAPHY

Design shallow, not steep, slopes.

C. SOILS

If you have an underlying impermeable stratum, do not excavate through it.

Do you need a liner?

 

Plant community structure:

D. REVEGETATION

See “Vegetation Requirements”

1. STRUCTURE

Spacing, vertical complexity.

2. SOURCES

Salvage, on-site, seeds, nurseries, propagation, wetland soil.

3. SPECIAL HABITAT FEATURES

What do you want to attract?

What organisms have had their useful habitat reduced?

Snags, open water, boxes, logs, islands, perch trees, etc.

4. HUMAN USE

What is the most minimally intrusive way to get humans into a site?

 

 

 

IV. FINAL DESIGN AND IMPLEMENTATION

Do earthwork, grading and excavation when it is dry.

A. CONSTRUCTION CONSIDERATIONS

1. EROSION CONTROL

Downstream sediment during construction will determine if you get your permit revoked.

Erosion control is a growth industry.

2. STOCKPILED SOIL AND VEGETATION

Salvaged vegetation may be retained on site if it is kept in shade and is watered.  Short shelf-life.

3. AMENDMENTS

Don’t use amendments.  Mulching is becoming more and more accepted as a good way to retain soil moisture during the dry season while suppressing weed seedling growth.

4. YARDS, ROADS AND EQUIPMENT

Soil compaction, root damage.

Petroleum product pollution.

Plant when it is wet.

B. PLANTING CONSIDERATIONS

1. SEEDING

At best, a secondary method in wetlands.  Seeds float off, rot, are eaten.

2. SPRIGS, PLUGS, RHIZOMES, TUBERS

Appropriate for many wetland plants.  But they can float.

3. CUTTINGS, LIVE STAKES

Cheap, prolific, usually sources nearby, hard to miss.

4. CONTAINER, BALLED AND BURLAP, BARE ROOT

Container plants are the most flexible plant form, and can be planted all year long.

Ball and burlap seldom used

Bare root is cheap, and works well where the individuals will not be threatened by water stress.

5. GENERAL

You may have to irrigate, even in a wetland.

                   Plant specifications from Stevens and Vanbianchi.

V. MONITORING

          Have a threshold set for replacing dead plants.

Likewise, have a threshold for the appearance of invasive species.  It should specify each species, at what level of invasion to act, and what to do.