The researchers used GIS technology to estimate how much water would run off in a specific area called the Northern Collector Water Tunnel. They looked at factors like land use, soil type, rainfall, and elevation to predict the amount of floodwater that would be produced. By analyzing all these factors, they found that the amount of runoff in the area is increasing slowly due to minimal changes in land use. During heavy rains, the volume of floodwater can be as high as 95,632,371 cubic meters, while during low rains, it can be as low as 7,120,686 cubic meters.