Decision Tree

What Is It Good For?

A decision tree can help identify what would happen under a variety of standardized alternative future scenarios. You can identify potential flaws and areas where more research may be needed. Adding the probability of outcomes helps give participants an overall view of what may happen under each alternative. This tool helps participants understand what would happen under various natural conditions, such as:

 
• Wet, average, and dry water years
• High, medium, and low water demands
• High, medium, and low population growth

As decision trees list all the alternatives being considered and their outcomes, they are also useful to keep the process on track. Participants can clearly see what the decision revolves around.

How Do I Use It?

 
1. Think of three or four possible scenarios for each alternative. Make the scenarios as consistent as possible between alternatives (for example, 100-year flood, 10-year flood, average flows).
2. Use the same measurements and analyses for each alternative.
3. Draw a square for each alternative.
4. Draw a circle for each scenario.
5. You can show further possibilities by drawing two ovals to show possible outcomes for each scenario (for example, in a high water year, this alternative may either flood the city or fill the reservoir, depending on previous water levels).

Go On