What is a space for time study and why do we use it?

BACI - Before after control impact Before you add measure you characterize everything. Then introduce measure look at the same reach and see the effects over time. The meassure is only introduces in part of the stream. Then the reach part without meassure is control. This is the strongest statistical meassure But it takes such a long time. So its maybe not the best strategy because it takes to long. Instead we use space for time. Instead of waiting, we look at similar streams. We select are group of streams that are for instance chanelized and a group with neanders that in all other aspects are similar and then we compare them. Then we assume that if we restore the chanalized streams they will turn into the same as neanders. When modifying remember what the reference stream looks like. Don't just drop giant rocks etc if they would not naturally be there. The reference site is basicly where do we want to be - how would they have looked naturally. Bottom right - to see if they are more or less equal. The letters indicate where they are different. We want them to mostly the same but of course if we change substrate then substarte will not be the same.