Analyzing Mitigation Success
The history for mitigation success has not always been good. Granted, we are all relatively new to this. Sometimes the failures are due to simple environmental variability—idiopathic dieback, storms, mechanical damage, or sea level rise. Sometimes restoration ends up being more successful by leaving it to grow back on its own! That is not always the case. Waiting up to a decade for a disturbed site to regenerate falls short of the objectives set by regulatory agencies and leaves a damaged site in less than optimal conditions for too long. The solution needs to be something that can fix disturbances quickly. We’re learning as we go. Here are some common, hard-learned lessons for restoration projects.
• Steep slopes guarantee failure.
• Designers need to visit the site in order to understand what must be done to restore it after construction.
• Surface drainage needs to be formed through sensitive grading that accommodates multiple lateral connections to the disturbed streams. Drainage needs to mimic a local, natural system.
• Soils can play a huge part in a working buffer or wetland system.
• Mitigation grading needs to fit the specific hydrologic position/phase in the watershed.
• Mitigation planting needs to fit the available moisture levels of the disturbed area.
• Artificial drainage modifications that previously existed on the site can reduce the effectiveness of your careful restoration and must be removed.
• Expect fluctuations in water level.
• Adjacent landowners can play an important role in preserving a buffer area.
• Our restoration projects need to somehow live beyond installation in spite of neglect.
• Engineers, hydrology experts, landscape architects, contractors, enforcement monitors, plant experts, and maintenance personnel need to work together, and any missing link in this team can bring the whole project down.
In a perfect world with unlimited amounts of time and money and harmony between the different professions and trades, all of these issues can be addressed easily. Until that time comes, we often need to use quick and dirty solutions that involve minimal budgets and unwilling partners. The answers for make-due mitigation fixes lie in old-fashioned horticultural practices and compromise. Good planting practices can be paired with practical trade-offs. Vegetative mitigation is still the best, least expensive method to heal a damaged site, but it will only work if there is adequate room to contour a workable mitigation site through sensitive grading. This is the best, realistic way to accommodate safety concerns and work within limited budgets.
You can find more information about trees in The Advanced Guide to Environmental Mitigation Planting: Healing Disturbed SItes, part of The Advanced Guide series.