Monday, September 13, 2010

The Greenbelt in September

Greenbelts sold Austin to me.  To be able to live in a city, yet to also have a trail that ran along a creek and through the woods within walking distance, felt like having the best of both worlds.  That first greenbelt was the Shoal Creek Greenbelt, a trail that I was walking and running within days of arriving in town.  It was along Shoal Creek that I first learned to recognize the pecan, hackberry, cedar elm, and mulberry trees of Austin, and to distinguish between the trifoliate leaves of wafer ash and poison ivy.  In the years between I explored abandoned sections of Waller Creek Greenbelt, was surprised by the length of Bull Creek Greenbelt, and stumbled across several neighborhood greenbelts hidden throughout Austin.  These days, the closest greenbelt to me, and the one that I travel the most, is the Boggy Creek Greenbelt, which winds along Boggy Creek from East 12th Street to Pedernales Street, creating a hill-free, pecan-shaded route from my neighborhood to east-side destinations below 7th Street.  But, while the Boggy Creek is "my greenbelt," it still isn't "the Greenbelt."

"The Greenbelt" is the Barton Creek Greenbelt, no matter where I live in Austin.  It is the longest greenbelt in town, and its creek, Barton Creek, is an order of magnitude or two bigger than Shoal, or Boggy, or the other creeks that wind through town.  And, unlike Shoal, or Boggy, or Bull Creek, which have been so thoroughly cemented that they begin to resemble over-sized drainage ditches along some stretches, Barton Creek is still allowed to be a creek along most of its length.  Which means that, just as the experience of walking the trail, defined largely by which plants are in leaf or bloom, is new in every season, the topography of the creek itself is reinvented every time it floods.

The Greenbelt has multiple entrances and many destination points, some of them publicly known, like the falls, and some of them private reference spots, like the mother cove, that I share with Lee.  In the car, heading down Mopac, we always debate which entrance to use and decide based on the season, the water levels, and our recent hikes.  This weekend, wanting to enjoy the water left behind by last week's tropical storm, we opted for the Mopac service road entrance and walked upstream, toward the falls.

The flooding last week was quite extensive.  Flood debris - branches, leaves, garbage - was stuck in the branches of trees 4 to 6 feet above the current creek level.  One of this summer's landmarks, a picnic table that used to sit on some rocks in the middle of the creek near a good swimming spot, had been carried about a half mile downstream, where it was lodged in a grove of young sycamore trees.  Along the trail, broken ragweed stalks showed where the water recently flowed, and a think, spongy layer of silt covered most of the ground between the trail and the creek.  I've seen a lot of floods along the Greenbelt, and a lot of flood debris work its way downstream, but I've never seen so much silt left behind by one flood.  I wondered what eroded upstream to create all the sandy soil that now covered the ground along the creek.

The creek was raging, calmed down from flood stage to fill its full creek bed.  The water was deeper than it had been earlier this summer and it was running stronger and cooler with the addition of spring water from all the mini springs along the creek that had been brought back to life by heavy rains.  We wanted to cross to the trail on the south side of the creek, so we squished through the silt on the bank and stepped into the rushing water.  Crossing was harder than it looked, partly because my great fear of drowning was activated by the knee-deep water, and partly because the creek bed was green and slippery from a season of fluctuating water levels.

Along the trail, the bright magenta berries of the American Beautyberry (Callicarpa americana) shrubs were the most visible color.  The berries, now almost ripe, will stay on the branches long after the leaves of the shrub have fallen, providing winter food for the birds along the creek.

American Beautyberry (Callicarpa americana)

Drummond's Wild Petunia (Ruellia drummondiana) was also in bloom at the side of the trail, adding purple to the shady spaces beneath the larger shrubs and trees.  (The picture below also captures some flood debris piled under the base of the plant.)

Drummond's Wild Petunia (Ruellia drummondiana)

Back on the higher elevation and more rocky north-side trail, on our way to the falls, we passed a blooming Lindheimer's Senna (Cassia lindheimeri or Senna lindheimeri) that was growing in the limestone soil.  The seeds of the fall-blooming Senna will provide food for the birds this fall.

Lindheimer's Senna (Cassia lindheimeri)

As we walked, we checked our favorite lounging-in-the-creek spots from earlier this summer, but the water was flowing too quickly, creating foamy rapids where the water crashed over rocks that often sit above the current.  In a few places, we waded into the creek to enjoy the cool water and the creek view, but we waited to jump in until we reached Sculpture Falls.  Refreshed, hungry, and nearing sunburn, we headed back downstream on the north-side trail.

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