Because you might have just done something different with the experiment and messed up someway during the test
If this is for the scientific process unit, the answer is passing laws to prevent certain types of scientific research. I know because I had this question in biology.
Low infiltration capacity means that the soil cannot absorb much water per volume. The first step in erosion in a landscape dominated by low-infiltration capacity is the raindrop splash. This is where raindrops displace the soil from their original place because the soil cannot absorb adequate amounts of water.
The official term is a megaflash :)
