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Design Collaboration: Creating Naturalistic Solutions for Stormwater Abatement, Alex Smith Garden Design, Ltd. Kristin Landfield

 

This morning, a spring storm is plundering the landscape. It’s a heavy downpour that’s lasted since early yesterday evening. As I hear it pummel the roof, I see the boughs of Beech trees weighted by the deluge. My mind quickly turns to places this substantial rainfall could impose some damage—active installation projects where I’m hoping the silt fencing will hold, plantings recently installed on steep slopes, and the culvert below my driveway that tends to back up. We needed some rain, but this 6-7 inches we’re getting today will overwhelm natural routes for sheet flow. On my morning walk, I noticed where a section of a stream has disappeared, even during this season of intense rainfall. It’s gone underground, not uncommon in this spring-laden locale. Torrents of water tearing down the bank have dislodged some portion of streambed and it’s now flowing underground.

Anyone who has witnessed a downpour in the Southern Appalachians recognizes the potency with which rainfall can travel down these rugged inclines. Water’s irrefutable force chisels a path into the landscape, demanding access to our abundant streams, rivers, ponds, bogs, and aquifers. Deep fissures and crevices score our local granite, signaling the unassailable power that can devastate a landscape when rainwater overwhelms the normal channels for runoff. In the wild, erosion can inflict irreparable injury to a stable ecosystem. When the natural rivulets and streams can’t support a rainfall, the banks collapse and uproot trees, thereby diminishing the forest’s natural defenses for the next big rain event, which further augments the problem.

Botanically, geologically, ecologically, this is an interesting phenomenon and aligns with climatology data that indicate Western North Carolina is receiving more erratic and intensive rainfall, with longer periods of drought in the interim. But these severe rain events create “downstream” effects, detrimental to our sensitive ecosystems, wherein one or two degrees in average stream water temperature destroys entire species of flora and fauna endemic to the Southern Appalachians. These intensive rains move too quickly to soak into the ground. Streambed silt decreases stream depth, thereby elevating stream temperatures. As torrents of rain strip the hillsides of topsoil and nutrients, our native trees and shrubs fail to thrive and reproduce the next generation of flora that would better moderate these effects.

So, this is the ecological and botanical backstory driving our collaboration with Southern Highlands Reserve (SHR) in a campaign to mitigate erosion and storm damage in their high elevation botanical garden. In 2019, SHR engaged Alex Smith Garden Design, Ltd. in a pruning remediation project. Since then, we’ve collaborated to assess and improve target areas in the Reserve with their talented team. SHR has been a sacred place for me over the last six years, since I first set foot on that enchanted property, so it’s been a great honor and privilege to be involved in such projects.

Because so much of our company’s design work integrates grading and drainage solutions, we’ve developed an aesthetic for achieving these erosion mitigation systems in a naturalistic way, the intent to provide both practical and attractive solutions with verisimilitude to the local topography. This endeavor dovetails with SHR’s mission to develop and steward a high elevation botanical garden in a way that refracts and interprets nature. With clear design intent and a light touch, SHR manifests aspects of these mountains that call out to visitors, accentuating the extraordinary features of the Southern Appalachian landscape.

Our joint focus has been aimed toward erosion mitigation using naturalistic boulders, streambeds, and channels to reroute and direct water in a way that supports and enhances the garden. Some of these solutions are underground, but many of these are visible, our intent being that these projects integrate seamlessly with the spectacular landscape that has been developed and tended over the last 20 years. SHR’s hydrology data and years of onsite observation have been pivotal resources to inform the areas we have targeted for grade remediation and erosion abatement. We love the challenge of simulating naturally occurring outcrops and rugged inclines with carefully placed specimen boulders.

So as this rain pours down, I reflect on the work we’ve done so far. It would be impossible to engineer a grading and drainage system for SHR that fully controls erosion without destroying the montane character that so defines the garden. At 4500 feet in elevation, receiving prodigious rainfall in single events, our shared goal is to suppress the detrimental and labor-intensive effects of storm damage and run-off, all the while maintaining the serene setting that infuses the land. This week, we will walk the tranquil property and let this latest storm be our teacher, advising and instructing on the work we’ve been so fortunate to perform.