Gullies blocked

Letter box gullies are blocked which causes flooding in heavy rain. I have attempted to clear two of the gullies by reaching in as far as possible, but carrier pipes are full of silt and road grit. Needs jetting please to improve outfall flow to watercourse. I know this has been reported before, and reply received stated the problem was not at intervention level. The pipes are blocked, i have cleared the first foot by hand but beyond that they are still blocked. So 'not at intervention level' doesn't make much sense. I also dug out the grips on the opposite verge to help alleviate the issue. The properties at Oak Range and Esperanto get the run off if this isn't sorted.