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The Great Hatchie Canoe Expedition -
Day 6: How Healthy Is the Hatchie?
Author: Monica Clutch
Date: March 3, 2008
Location: south of Brownsville, TN
Photo © Monica Clutch/TNC
Previous entries in the blog
The morning of Day 6 of the Hatchie Expedition we had a forecast of warm weather in the low 60s and rain that was supposed to be light and sporadic. Unfortunately, the day started off with a flat tire on the canoe trailer. I was already running late due to the fact that it was raining, which made getting the truck and canoe trailer out of my mother’s backyard more challenging than usual. Fortunately, if a flat tire can have a fortunate aspect, the tire went flat as I was pulling into a gas station so not only was I not stranded at the side of the road, but there was quite a bit of readily available help with more brawn and tire-changing experience than I can claim. Poor Mike Martin was already waiting for me when I called him and told him I was further delayed. The other fortunate situation was that I had finally bothered, just three days previously, to replace the dry-rotted spare with a new tire. What serendipity!
I did finally catch up with the ever-patient Mike near the Hatchie National Wildlife Refuge canoe put-in before we made our vehicle swap & drop for the day. It was raining and I was muddy and wet before we even unloaded the canoe. Still, this was undoubtedly my favorite leg of our journey so far. Besides the fact that Mike and I seem to have finally mastered attaching the canoe to the top of his Jeep and that neither of us ended up lying on the ground, in a canoe, in the river, or in some other humiliating position, there were many reasons to enjoy the day. In fact, the rain — harder at some times, gentler at others — provided a peacefully insulating screen that enfolded us in quiet serenity of the floodplain, seemingly away from the noises and worries of the world. We saw few signs of activity throughout the course of the day — except for that of beavers, birds, and turtles. The air was ripe with the scents of decomposing vegetation, an earthy blend that took me immediately back to childhood memories of playing outside — a time when I did not hesitate to sink to my knees in the mud, dig my toes into a soft carpet of moss, or scratch my hands and knees as I tried to scale a promising tree.
A beaver's handiwork on shore. Photo © Monica Clutch/TNC
A River Otter Joins Us
Mike and I were further rewarded for our persistence on the journey (despite the day’s earlier frustrations) with the rare sighting of a playful river otter. Its head popped up early on our journey within the bounds of the Hatchie National Wildlife Refuge, and it swam somewhat ahead of our canoe in a cautious, yet watchful manner. It quickly became evident that the creature was not a beaver or muskrat as it rolled into a playful dive and re-emerged several meters downstream. It continued this frolicking dive-emerge sequence, teasing us with glimpses of its adorable face, until at last it tired of our presence and silently vanished into the river.
I mentally replayed that otter sighting over and over for the rest of the trip, commenting to Mike periodically on how fortunate we were to have seen the playful mammal in its natural habitat. I thought some more about the necessity of protecting entire ecosystems on a landscape scale as habitats for plants and wildlife. As we passed an impressive stand of river cane, I considered how it was not enough to protect a single site, such as a wildlife refuge, in order to protect species biodiversity, but how it was essential to understand the entire landscape context of a site, which would include its relationship to other sites with which it interacts. In a recent research presentation that I attended, the speaker explained how river cane seems to be an important habitat for the Swainson’s warbler, one of the most threatened migratory birds nesting in the southeastern U.S. In that particular study, almost no Swainson’s warblers were found in sites without river cane. Despite its total size of more than 11,500 acres, the Hatchie National Wildlife Refuge is only a small fraction, less than 10 percent, of the 1,664,000 acres that make up the Hatchie River’s watershed. I thought back to a discussion Mike and I had on our last canoe trip along the Hatchie:
For as long as it survives, the Hatchie National Wildlife Refuge is as good an example of a functional and pristine bottomland hardwood forest habitat as we have in the Southeast. I have to emphasize the phrase for as long as it survives. I have to qualify this statement because, as Mike and I discussed on the river that day, things are not always as they seem when it comes to health of an ecosystem.
Ranking the Hatchie on a 1 to 10 Scale
Our conversation began with Mike asking me, as an ecologist, how I would rank the Hatchie on a scale of 1 to 10 in terms of river health. I must admit, I have considered the question before. As we paddled downstream enjoying the rise and fall of the river in response to rain, observing wildlife, marveling at splendid tree specimens, and delighting in surprises like the river otter we saw, and knowing that the Hatchie is one of the sole surviving examples of an unchannelized river with a largely intact floodplain and a natural flood regime, it was easy to feel self-satisfied, thinking everything was fine and good with the Hatchie River. Yet, having spent so much time out in the river’s watershed, exploring tributaries and building restoration projects, I am very aware, as are many of my inter-agency colleagues, that the Hatchie River is suspended in a fragile balance right now. It, like so much of our natural world, teeters on the brink of existence, always in danger of going over the tipping point, beyond which return to desired conditions is so difficult and expensive to achieve.
Yes, it is a beautiful river and home to many interesting and rare plant and animal species. Still, I would only rank it a 7 out of 10 in terms of river health.
The bottomland hardwood forests creating the floodplain of the Hatchie River are shrinking annually. Statistics exist for the land of the Hatchie National Wildlife Refuge. One does not need to travel far throughout the floodplain to find stands of dead and dying timber. This is great habitat for woodpeckers (such as the flashy and graceful pileated woodpecker) as well as for wood ducks and other cavity-nesting species. Unfortunately, this type of dying forest habitat seems to be in abundance lately as the lengthening duration of flood events causes water to stand in the floodplain for longer-than-normal periods of time. This flooding can be caused by beaver, and we did find evidence in many areas of beaver activity. This can also be caused, as is common in the Hatchie River's watershed, by excess sediment being carried along with water.
Woodpecker cavities in this Hatchie tree. Photo © Monica Clutch/TNC
The Problem of Excess Sediment
Sediment builds up on the floodplain and within tributaries, arresting the flow of water and thus preventing it from draining off at a normal rate. The region’s sandy soil itself can even smother the roots of trees. That’s because they have adapted over the millennia to standing in moist, silty-sand and silty-clay soils with high organic matter content, but they are not adapted to dealing with tons of smothering sand around their roots.
In my previous blog entries I have discussed the origin of these sediments. Hatchie tributaries — channelized decades ago in a misguided attempt to control flooding — have rapidly destabilized. As their channels eroded their way into the uplands of the floodplain (a process known as “headcutting”), sediments from unstable streambanks and from within the eroding channels themselves (“bedload”) are released into the water during rains and transported downstream to the Hatchie River. Eventually these sediments are transported from the Hatchie all the way to the Mississippi River and Gulf of Mexico, where they cause further problems.
In a domino effect, an unstable stream bank causes further destabilization of surrounding streambanks, leading to over-widening of the stream channel. Downward scouring in the channel bed, as a headcut progresses upstream, leads to further destabilization and downcutting of the channel bed to allow excess incision of the stream channel. The Hatchie River has 33 major tributaries — all but one of which have been channelized, and all but one of which are experiencing at least some degree of over-widening and channel incision. So there is a great deal of sediment making its way into the Hatchie River.
An impressive sand bar, the result of erosion and sedimentation in the Hatchie. Photo © Monica Clutch/TNC
Looking at the Big Picture
I will leave the reader with this thought, these last two blog entries being very heavy on science. The long-term sustainability of the Hatchie is tied to so much more than the river’s mainstream and its banks. The survival of the Hatchie depends upon the conditions of the entire watershed, from the most intermittent drainage ditch or headcut in an agricultural field to the use of best management practices in upland forestry operations or proper construction of roads and bridges.
While it may seem like a tremendous amount of responsibility is required on so many different fronts to maintain this ecosystem’s health, I remain an optimist when it comes to the Hatchie River. I find that most of our partnering agencies understand the problems facing the Hatchie and stand ready to form task forces that will maximize conservation dollars. In fact, we are already making progress in such joint efforts. Additionally, the increasing willingness of private landowners to include conservation in their land-use plans is changing the conservation scene for the better for people and nature.
On to Day 7...
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