Detective 4

The graphs below shows the relationship between IBI and land use in the riparian zone.  A higher number means more of the 150 feet on either side of the stream is occupied by that land use.  The numbers are in percentages.  Study the graphs and answer the questions.  Be prepared to explain the correct answers to your group.


Watershed Glossary

  1. Describe the relationship between urban riparian land use and IBI - as the urban land use percentage goes up, the IBI ??.  
  2. Describe the relationship between the other land uses and IBI - as the agricultural or forest land use go up, the IBI??
  3. Where are the places/times where the relationships do not seem to be consistent on the line graph?  Write those down.
  4. With high urban land use in the riparian zone, we would expect an impact on the biology because:

    - There will be more urban stormwater runoff from streets with a lot of pollutants

    A is only partly right - This is true but some other things also occur.

    - There has probably been major modifications to the stream in the riparian zone like straightening, removing vegetation, and covering the banks

    B is only partly right - This is true but some other things also occur.

    - There are more people fishing in the stream

    C is incorrect - There will actually be fewer fish because of habitat changes.

    - Both A and B

    D is correct -
  1. The IBI should be better if the percentage of forest in the riparian zone is higher because:

    - Forest areas produce higher sediment loads

    A is incorrect - Actually sediments are reduced by forests.

    - Trees in the riparian areas shade the stream and keep it cooler

    B is only partly right - This is one reason but there is another one as well.

    - Tree roots purify the stream water

    C is incorrect - The trees protect the stream but do not directly filter the stream water.

    - Trees stabilize the banks and filter sediments

    D is only partly right - This is one reason but there is another one as well.

    - B and D only

    E is correct -