science 9 river testing

I had two hypotheses on what caused the formation of rivers. The first hypothesis is how do buildings and new developement effect the formation of rivers. We put styrapoam in the middle of the tub and the styafoam acted as the buildings. We poured he water down at an angle and it made tributaries around the buildings so now we know that buildings an new dievelopemnt do effect the formation of riers. The second hypothesis was if dams reroute rivers. Are two hypotheses are similiar, but still they are a little bit different. We found out the same result as the first hypothesis and that it did reroute the river.