AUSABLE WATER WISE: Think like a river
My college professor, adviser and mentor, Dr. Peter Allen, would often say, “You need to think like a river,” during our field assessments of urban streams damaged by rapid growth in the Dallas-Fort Worth Metroplex.
This was his way of prompting me to think about why the channels widened and banks eroded in response to changes in the watershed. It’s something I always try to remember, as a scientist who still spends his days trying to read the landscapes formed by rivers and streams.
The AuSable River has been here since the glaciers receded at the close of the Pleistocene Epoch, sorting through the chaotic debris left behind and slowly making its valleys deeper and wider. I often wonder what the river is thinking and what stories it might tell. I think about what the river must have been like in its wild youth, ripping down through the barren, mountainous landscape that emerged from nearly 100,000 years of icy interment beneath the indescribable weight of 5,000 feet of frozen water. It would have been joyriding down rocky slopes, careening off boulders, and plowing through sand terraces before debouching into the frigid waters of the massive glacial lake that once filled the Champlain Valley.
I imagine the river matured a bit as the landscape became covered with grasses, shrubs, and trees. It still ran wild on occasion, but the vegetation would have started to claim its share of the water budget that the atmosphere doled out each year. Before the trees grew, every rainfall triggered a frenzied floodscape. The plants brought some stability and forced the river to settle down a bit, sort of like being middle aged. Being young and wild is a rite of passage, but I imagine the river came to enjoy the company and the calming presence of the great trees that came to fill its valleys.
As the river grew older and its surroundings teemed with life, it must have basked in the sounds of songbirds and chuckled at the wolf pups playing along its banks under the watchful eyes of their mothers.
What did it think when people arrived? It must have felt some trepidation as these new creatures took such an active role in managing the landscape. Beavers do that, too, and the river didn’t mind them so much, but these were different animals. How did it feel when they began stripping away the giant trees? Perhaps it thought back to those early days of wild floods running fast and loose down the valley, but it was older now and the allure had long since passed. There is something reassuring about being in the company of large, old trees, and the river must have felt lonely once they were all gone. To make matters worse, these new animals were making the river do things it didn’t want to do. Straightening the meanders and dredging the channel to accommodate log drives and more roads and settlements. They even did things that made it difficult for the fish to live in the river. The deep pools filled with sediment washing off the treeless landscape. The forested banks that shaded the river to keep it cool in the summer were now barren. As much as the river loved the trees, it adored the fish. It nurtured them from eggs to adults and must have felt unimaginable sadness as they dwindled away.
So, what is a middle-aged river living on the fringes of civilization to do? Life moves forward one day at a time, same as it ever was. The river knows that time is on its side. It has been here for thousands of years and will continue to flow for thousands more. And someday, this area will be buried under ice once again. The river will be snuffed out along with everything else that is here today. Then, the ice will recede, and it will be reborn, just as it has been many, many times over the past two and a half million years. It is certain of this fate because the billion-year-old rocks that form the skeleton of this landscape told it so. These rocks have hunkered down and borne the weight of the ice sheets each time they came, grinding and gouging their way across the landscape. The river has certainly heard the tales of ice ages told by the rocks.
As a geologist, I spend a lot of time trying to understand the long, complicated stories of rocks and rivers. There is much we can learn about the past, present, and future that we share with them. To live with a river, we need to understand how it thinks, why it behaves the way that it does, and what it can teach us about our role as citizens of its watershed.
(Gary Henry is the stream restoration manager at the Ausable River Association.)