Teacher Site Map
8th Grade Core
USOE Science Home Page

Dams, Road Building And The Environment

For centuries, dams, roads and bridges have been built across rivers. These structures allow water to be trapped for drinking, recreation and irrigation water for farming. They allow people to cross rivers and transport supplies from city to city. An important use of dams is the production of hydroelectric energy. They are also used to control flooding. Unfortunately, dams and the roads that cross them can harm the environment. Because of these problems, people are looking to find alternatives to dam building. Alternatives to hydroelectric dams include alternative energy sources like wind and solar power.

Floods occur when there is rapid runoff of water, sometimes including dirt and large debris. Dams help control flooding by collecting runoff and debris. This debris includes rich sediments that at one time enriched farmland and built beaches with sandy runoff. To control floods, flooding waters can be slowly released through dam floodgates. Because of this, dams are usually very successful in controlling floods.

However, sometimes people become over-confident when building dams and good ecological and engineering practices are no longer followed. For example, dams have given people the confidence to build in areas that once were too close to rivers and flooding. Unfortunately, no dam can completely control river waters. There is always a chance that the dam will break. If this happens, the rapid rush of river waters can destroy homes and businesses in the floodplain.


Because of the ecological problems of dams and road building, people are looking for alternatives or ways to minimize their impact. When roads and dams are built, they affect the habitat of fish, birds and other animals. Reservoirs that fill up behind a dam can displace homes, farms and people.

The costs of dams are very expensive. Because the cost is so high and the problems so varied, people are looking for other methods to control floods and produce energy. Erosion prevention methods, like good logging and farming practices can help prevent flooding from occurring in the first place. Alternative energy sources for power production can reduce the need for hydroelectricity. By reducing the need for dams, roads, and other man-made structures, we reduce the environmental damage that they cause.



  1. List several reasons that people are looking for alternatives to dams?
  2. List two alternatives to hydroelectric energy.
  3. What is the problem with dams trapping debris from rivers?
  4. List a negative aspect of dam and road building on plants and animals.
  5. Explain an alternative to dam building that also prevents flooding.


Suppose that your town was considering building a dam on a river near you.

  1. List the pros and cons of dam building.
  2. What members of the community might be opposed to building the dam?
  3. What members of the community might be in favor of building the dam?

Review Science safetey rules here.

Get the plug-ins: Get Adobe Acrobat Reader , and Get Quicktime Player. (The QuickTime plug-in is needed to play sounds and movies correctly.)

Want to share photos of you or your friends doing this activity? Send it in an e-mail with the following information:

  1. The title of the activity
  2. The URL (Internet address)
  3. Your name.

Remember that no pictures can be used that show student faces or student names on it. 

Teachers should view the Teacher Site Map to relate Sci-ber text and the USOE 8th grade science core.

Updated October 24, 2008 by: Glen Westbroek

Science Home Page | Curriculum Home Page | 8th Science Core Home Page | USOE Home Page

Copyright Utah State Office of Education.