**By John Niemoth**

**Introduction**

There are several different river system patterns, in which it may be difficult to illustrate the different patterns associated with a hands on lab activity. The dendritic river system can be easily demonstrated on graph paper. Other river system patterns may be developed if time permits. A tree like drainage pattern is the dendritic river system, which is common for most free flowing water drainage systems in the mid plains region.

This lab is an open ended lab with the ability to graph other drainage systems after making modifications to fit the desired drainage pattern.

**Dendritic River System**

To illustrate the shape of a river system can be a great learning tool that the students can make in class or a home. It kind of represents a casino by throwing dices. It involves lines on graph paper and looks like a tree when through. This may be used in Earth Science, wetlands and water projects, etc.....

**Time**

30 minutes or longer, etc.

**Materials**

- graph paper
- one dice per group of two
- pen or pencil

**Directions**

- The graph paper is in the vertical position
- Put several lines across the very bottom to illustrate a larger stream or river.
- Put 20 dots at random throughout the graph paper on the intersections. The tree like pattern would be more dramatic if the dots were on the top half of the paper.
- Then a person rolls the dice and draws a line on the graph paper with the following directions. See end of page.
- The movement is started at the very top going row to row and from left to right like reading. May need to use a piece of paper to keep the students attention on row by row. Once you start a dot on a row, you never leave it when you go to the next row. Also, be sure they complete all the dots on the row before going to the next row. When times when you row a dice. For example, if three lines are together and the dice rolled was a one, you draw three lines three squares down so you don't have deal with that line until you get three lines down.
- dice 1-2 go straight down one square
- dice 3-4 go diagonally to bottom-right one square
- dice 5-6 go diagonally to bottom-left one square

**Suggestions**

- May want to put each dice in a baby food jar so that they don't get lost or thrown off the table. This tends to keep a roll of the dice at random since there are no hands on the dice.
- The dots may be located at the top third of a graph paper to allow for a better pronounced river system if desired to. The graph paper should be 4-5 squares per inch for the younger grades.
- To keep students from getting one row of dots or lines mixed up, put a piece of paper on top of the graph paper so that only one row of dots or lines are visible. This way, they only lower it when they get to the next row. An exception to this is when more than one dot or line meets, in which the line moves down the same number of squares as there were lines or dots that came together. Remember to draw as many lines or dots that came together when doing this. Therefore, if two lines came together, the next roll will result in two lines being drawn twice as far.
- Streams do not cross each other when they come together. They tend to follow the direction of the larger stream or river. If both streams are the same size, the direction of flow is up to the participant if they meet.
- The usage of a pencil for this activity is preferred for the younger grades or erasable ink for mistakes, which is common for the first timers.

Student copy that lists the materials needed and the procedure is on the next page.

**Conclusion**

Since students are learning a different technique, frustration can occur if they make too many mistakes early in the lab. Have students who finish early help those who are having trouble. This helps to eliminate the need to finish early or for competition. The students can associate river system patterns better after completing this lab.

For further study, this type of lab leads into the drawing, and interpretation of topographic maps. The identification of the different types of terrain on topographic maps.