"From Mount Holyoke is seen the richest prospect in New England, and not improbably, the United States...The variety of farms, fields, and forests, of churches and villages, of hills and valleys, of mountains and plains comprised in this scene can neither be described nor imagined. But the most exquisite scenery of the whole landscape is formed by the river and its extended margin of beautiful intervals...It is generally one fourth of a mile wide; and its banks are beautifully alternated with a fringing of shrubs, green lawns and lofty trees. Here spread also vast expansions of arable ground in which the different lots exactly resemble garden beds, distinguishable from each other only by the different kinds of vegetation, and exhibiting all its varied hues from the dark green of the maize to the brilliant gold of barley. A perfect neatness and brilliancy is everywhere diffused, without a neglected spot to tarnish the luster or excite a wish in the mind for a higher finish. All these objects united present here a collection of beauties to which I know no parallel. When the eye traces this majestic stream, meandering with a singular course through these delightful fields, forcing its way between these mountains, exhibiting itself like a vast canal...when it marks the sprightly towns which rise upon its bank... It will be difficult not to say that with these exquisite varieties of beauty and grandeur the relish for landscape is filled, neither a wish for higher perfection, nor an idea of what is remaining in the mind." Timothy Dwight Travels in New York and New England, 1821

Rivers are dynamic. As they flow, they are constantly cutting, scouring, depositing and reworking the landscape. It's a process that can seem infinitely slow and its effects are not always apparent--even at the river's edge. But, when viewed from the air, the curves and abandoned oxbows, the point bars and islands reveal how rivers modify our landscape.

If you were on the banks of the Connecticut River 12,000 years ago, you would be under about 200 feet of water. This was a time when a giant glacial lake, extending 150 miles from northern VT to Rocky Hill, CT, filled our valley. The lake drained about 10,000 years ago, and since then the CT River has been meandering over the old lake bed, laying down thick deposits of rich river silts and making the valley one of the best for farming in all New England.

All rivers tend to flow in a sinuous pattern. But just what path a river takes depends on many factors--the climate, the erodibility of the surrounding landscape, the shape of the channel, the amount of water and its velocity. As the water moves downstream, complicated eddies and spiraling currents create turbulent flows that loosen and lift sediments as they pass. If the bank is made of easily erodible material, the force of the water tends to cut it away. On the opposite side of the river, the current is slower and sediments settle out and build up.
Over time, the curves grow larger and develop into enormous loops. Eventually the river loop is cut off and an oxbow lake is formed. The creation of the Northampton Oxbow in 1840 shortened the river's length by 3.5 miles.
There are areas of the CT River where another loop is forming. The bank is being actively eaten away by the river and is collapsing into a series of step-like terraces. Most of this erosion happens during flooding. Although right now the CT River is low, major storms and spring thaws can easily overtop this bank. In fact, floodwaters from the largest storms in this century were about this high.

This natural phenomenon of bank erosion provides key breeding sites for many creatures, the most familiar of which are bank swallows. Understanding the biology of these birds and why they select particular eroding banks is the current focus of biologist Mara Silver.
These streamlined insect eaters return in the spring and begin excavating nesting holes in freshly eroded river banks. Depending on the availability of suitable nesting sites, the size of a colony may vary from a dozen pairs to several hundred. Using their bills, the mated pair tunnels in 20-40" and then carves out a cavity where 5-7 eggs are laid on a bed of loosely arranged grasses. Although the erodibility of these banks leads to the loss of some nests, the advantage is that this is a hard place for raccoons and other predators to get a meal. Once hatched, the nestlings are fattened on insects and, early August the parents and offspring gather by the thousands to begin a long migration back to South America where they overwinter.

Eventually the river bank it will either collapse and form another steep bank for next year's colony, or if the river stops cutting here, it will become covered with vegetation. Bank swallows evolved the flexibility to shift from one nesting area to another. Typically the new nesting ground is found in the same stretch of river, but can be several miles away.
The one constant of a naturally flowing river is CHANGE. Banks erode, beaches form, floodplain forests develop, only to be eroded again centuries later. This beautiful and dynamic system of shifting habitats is critical to the survival of many of our specialized plants and animals.

Questions and Activities after Watching the Video:

1. What’s the evidence that a glacial lake (Lake Hitchcock) once filled much of the Connecticut Valley? (Try to find some information about the varved clay deposits, deltas, beaches, and sand dunes that are found in the valley.) Would your community be completely or partially covered by the lake if it were still here today? (The shoreline of the lake was near the present day 300-foot elevation in the Northampton area but further north shoreline deposits show up at much higher elevations because of a phenomenon called post glacial isostatic rebound. What’s that?) Make a map that shows the shoreline of Glacial Lake Hitchcock in your community.

2. The Northampton Oxbow is a famous historic example of a river loop that was cut off. Can you find any evidence of more ancient oxbows along the Connecticut River? (Topographic maps work best for this. Look for large curved areas on either side of the river.)

3. Can you predict a spot where another oxbow will be created sometime in the future? What could you present as evidence that your prediction is likely to happen?

4. Other birds nest in river banks. What are they? How do their nests and habits differ from swallows?

5. At first glance it may seem that stabilizing an eroding bank with rock or other debris would always be a good idea. There are, however, several good reasons why this technique could be a very bad thing to do. What are some of the advantages and disadvantages of river bank stabilization projects? What other options are available, other than rock riprap?

6. One of the best ways to understand the characteristics of flowing water and its ability to erode and meander is to set up a classroom streamtable. A stream table, a pump and a few bags of diatomaceous earth might take a few hours to set up, but it’s worth it in creating a miniature system for displaying river dynamics.

 

Curriculum Resources: Bandolin, Larry et al.1995. Final Action Plan and Environmental Impact Statement for the Silvio O.Conte National Fish and Wildlife Refuge. Turners Falls, MA: US Fish & Wildlife Service. (H) Kaufmann, Jeffrey S. et al. 199x. GEMS River Cutters (Grades 6-9). (H) Themes covered include river dynamics, river features, mapping, dams, erosion, sequencing geological events, pollution, and human effects on the environment. Each activity is between 45-60 minutes in length and focuses on different skills, such as data collection, experimentation, communication, decision-making and model design. A glossary of terms and data sheets are included. Terrific resource. Adopt-A-Stream. 1992. MA Division of Fisheries and Wildlife. Contact Joan Kimball at 617-727-1614 X 360 (H) An action-oriented program to protect and restore MA rivers. Students could collaborate with watershed groups, town conservation commission's or angler organization to help identify problems and resources along selected rivers. American Rivers, 801 Pennsylvania Ave., SE, Washington, DC 20003 For information about the condition of our wild and scenic rivers. Randolph, Bill. 1997. River Education Awareness Program. A curriculum guide to the Mill River, Springfield, MA. A collection of resources and activities that rely on simple, inexpensive tests to monitor water quality. Many extensions to other disciplines. A great way to develop or expand a watershed/river curriculum. For more information, call 413-263-6800 x 404.