We had a significant leak from this trough section of flat roof on the right side of the garage door, either around the scupper or from backing up under the edge of the shingles; rain ran down the inside of the garage wall and was eroding the sheetrock. Jesse suggested having a metal cap built to go up under the shingles and then over the entire corner to deflect the water. I opted for having him fill in the whole trough with spray foam insulation and close off the scupper.