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Human Environment Interaction

Norma Lou Blake and Douglas R. Miller

One of the longest ongoing relationships has been between people and their rivers. Illinois rivers have played an important role in the lives of its people, and people in turn have altered the rivers, with consequences both positive and negative.

Most of the cultural imprint on our landscape has a historical basis in Europe. With a very high population density, Europe has the most transformed landscape in the world. Little of its physical base has escaped the effects of civilization. Similar methods were employed in the North American colonies, and the European cultural imprint diffused westward along with manifest destiny. Settlers of mostly western and central European stock eventually came to the land that would be called Illinois. They cleared, excavated, drained, and in other ways altered the environment. And they left their mark on the rivers and streams.

Rivers are one of the most important physical components of a region. People have used rivers for a multitude of purposes, such as transportation, recreation, and a source of food. It should come as no surprise that the history of a region is often intimately linked with a river nor that humans have long modified rivers to improve upon the capabilities of those vital resources. What many people do not realize is that a river will adjust to those changes, often with unexpected and unpleasant consequences.

Most of Illinois' streams are part of the Mississippi River drainage basin. Only a few short streams flow into Lake Michigan and eventually into the St. Lawrence River. The state's settlement pattern clearly shows that Lake Michigan was more of a magnet for people than the Mississippi. Yet the Mississippi River system was very important.

Native Americans, explorers, fur trappers, and traders all made use of this river network. The rivers provided access for early settlers to the new frontier. As settlers cleared land and grew crops, rivers and lakes carried supplies, delivered crops to markets, and floated logs to sawmills. The downcutting of the river exposed a variety of resources along the banks, including clay, rocks, coal, and minerals.

The Mississippi offered numerous opportunities, but it was a hazardous stream to navigate and caused serious problems for navigators. Particularly hazardous was an eleven-mile-long stretch of rapids between Hamilton and Nauvoo. That reach of the river is in a gorge and flows over

State of Illinois
Human Environment Interaction

Humans and

All places on the earth have advantages and disadvantages for human settlement. High population densities have developed on flood plains, for example, where people could take advantage of fertile soils, water resources, and opportunities for river transportation. By comparison, population densities are usually low in deserts. Yet flood plains are periodically subjected to severe damage, and some desert areas, such as Israel, have been modified to support large population concentrations.

Cultural and Physical Relationships. People continue to modify or adapt to natural settings in ways that reveal their cultural values, economic and political circumstances, and technological abilities.



limestone. Glaciers were instrumental in creating that reach by changing the course of the ancestral rivers that flowed here. The Hamilton-Nauvoo stretch is a relatively new channel; the water has neither eroded the bedrock nor carved a broad floodplain, which is characteristic of the river above and below the rapids. The rapids so disrupted traffic on the Mississippi that cargo often was off-loaded at one end of the rapids and carried by some other means to the other end, where it was reloaded onto boats or barges.

As riverboats became bigger and were powered by steam, the Hamilton-Nauvoo gorge and other hazards on the Mississippi posed so many transportation problems that the federal government began modifying the river to improve navigation.

The Army Corps of Engineers has engineered a variety of projects to control and confine the river. The rapids at Hamilton were the Corps' first project because they were the first permanent obstacle to navigation upstream from New Orleans. The lock and dam that we can see on the river at Hamilton is the last of three major construction projects at the site. (A lock is a device that lifts or lowers a vessel from one water level to another in order to permit navigation through a dam.) Work began with a survey in 1829. Two more surveys (one led by Lt. Robert E. Lee), along with a futile effort to blast a channel into the rock of the river bed, resulted in no significant progress until after the Civil War.

In 1867 work was started on a five-foot-deep channel with three locks to bypass the rapids. The 78-foot-wide channel opened to traffic in 1877. Total lift throughout the canal was nearly 19 feet. The facility included the only dry dock above St. Louis. (Total lift refers to the difference in elevation a boat is lifted or lowered through a lock or series of locks. A dry dock is a facility that enables a boat to be supported in a water-tight enclosure; water is pumped out of the enclosure permitting maintenance to be performed on the hull below the vessel's waterline.)

In 1899 it was decided to build a dam across the river. While the dam's main purpose was to generate electricity, it would also flood the rapids. A three-lock canal with one 38-foot lift-lock would replace the old locks. Construction began in 1913, and the lock opened to traffic three years later. The dam's dimensions were seven feet deep, 110 feet wide, and 400 feet long. The lock served for forty-four years, but as other larger locks were constructed up and down the river, the 1913 facility eventually became outmoded as river traffic increased and vessels and barges became larger.

Planning for a larger lock began in 1940, construction began in 1952, and the facility was completed in 1957. The new lock, still in use today, has a channel 1,200 feet long, 110 feet wide, and 13 feet deep, and the same lift of 38 feet. A fifteen-barge tow can be locked through without breaking it down. A typical locking operation takes approximately thirty minutes and in the process either fills or empties the lock channel with 38 million gallons of water.

Today, there are twenty-nine locks on the upper Mississippi River; fifteen are along the Illinois shore, and the southernmost one is at Granite City, Illinois, near St. Louis. Those incredible engineering feats are a good example of humans modifying their environment to serve their needs.

Workers were needed to make those improvements, and improved transportation in turn attracted new industries and more workers. Many river improvements were undertaken during the Great Depression when the federal government budgeted billions of dollars for public work projects, which included wages for many workers. Because special equipment was needed for some operations, new factories were created. Industries located near rivers, not only because they provide energy, but also because water transportation is comparatively cheap, especially for hauling bulky, non-perishable goods.

Much of the grain harvested in America's interior is delivered to elevators along the river where it is loaded on barges bound for New Orleans and shipped to all parts of the world. Crushed rock, sand, limestone, coal, petroleum products, and scrap iron are some of the materials that can be economically shipped on the river and done so more reliably because of locks and dams.

The slack-water pools created by dams have encouraged various forms of recreation boating, water skiing, fishing, and hunting. Scores of marinas and sports shops and a host of other retail stores cater to the needs of those who spend their leisure time on or near the river. Recently, gambling has attained new popularity on replicas of the riverboats that once plied the big rivers.


Engineering projects have not been restricted to the Mississippi River. Its major tributaries have been similarly modified. Both the Illinois and Ohio are hard-working rivers; the Illinois transports more river tonnage than the Mississippi above their confluence. The Chicago River is connected to the Illinois by the Chicago Sanitary and Ship Canal, creating a link between the Great Lakes and the Mississippi, which gives Chicago and its industries access to two vast transportation systems.

Rivers and streams provide a great deal for people. Geographers and historians agree that a country's or region's livelihood, prosperity, and strength are directly related to their river systems. It would be difficult to imagine Europe without the Rhine or the Central United States without the Mississippi. Life would surely be different. As we have seen, humans have modified their rivers and streams to gain even more benefits, but these benefits have not come without costs.

Engineering of waterways has brought immediate direct rewards to humans, but long-term costs are often not so apparent, particularly to the environment. A stream is a complex natural system; it has inputs, outputs, energy, throughflow, and storage. It will adjust to the modifications humans have made, attempting to achieve equilibrium between its components. If any component of a stream is altered, disturbing its equilibrium, the stream will adjust to regain that balance. This adjustment can take a long time, and the results can be unforeseen but significant.

Sediment is a major problem. A river system is more than running water. It carries a tremendous number of sand, silt, and clay particles. In a free-flowing river, those sediments are either carried downstream, or they settle depending on the velocity of the water. During floods, when a stream spills over its banks, the sediments are deposited on the floodplain. Those particles contain plant nutrients that contribute to the general fertility of the soil, which explains why the land along rivers is some of the world's most desirable agricultural land. Sediment also nourishes wetlands with fresh nutrients that are needed at the bottom of the food chain to keep ecosystems healthy.

Dams are sediment traps, which leads to several negative consequences. First, the sediments that are impounded behind a dam cannot nourish the floodplain and wetlands as they do in a free-flowing river which leads to a decline of quality. The classic example of this decline is the lower Nile and its delta, both of which have been denied sediments since the construction of the Aswan Dam. The agricultural lands along the river need ever-more fertilizer to be productive, and the rich delta lands are receding because the balance between sediment supply and sediment removal by ocean currents is tipped in favor of the currents.

In addition, as sediments accumulate behind a dam they reduce water-storage capacity. That limits the effectiveness of a dam for flood control. The buildup can attract different species of plants and alter the ecosystem. Above the Hamilton Dam, water lilies have steadily been proliferating outward from shore in water that is becoming more shallow. This environment is growing less attractive for many species of fish enjoyed by fishermen. It is even less attractive for people participating in a variety of water sports. The buildup of silt covered the water supply inlet for the city of Hamilton, which was originally upstream of the dam; it had to be relocated below the dam.

Another modification found along streams is the levee. These earthen barriers have been constructed to confine the water to the main channel, preventing flooding. The benefits here are obvious; farmers do not have to contend with water-saturated fields. Tilling and harvesting can be scheduled more to their liking, and there is not as great a concern over crops being destroyed.

Again, those alterations are not without costs. Floods and the veneer of sediments they deposit are what made the land fertile in the first place. Levees block that cycle. After repeated harvests the soil wears out, causing the farmers to become more dependent on fertilizers. We now know excess fertilizers work their way to the river, leach into the water supply, and often cause biochemical reactions that have a negative effect on a stream's plants and animals.

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