What are the possible problems arise if we maintain slope opposite to the flow direction of water ?
It depends on what type of water, but I will assume it is either storm or sanitary flow or possibly stream flow. Secondly, I will assume that this is in a pipe or culverted stream. A negative slope would cause low velocities. It is not recommended that velocities go below 2-3 feet per second in most collection systems because the sediment (solids) will drop out and clog the pipe. Eventually this will lead to a blockage in the system. Second, depending on the amount of negative slope and type of water (sanitary sewage) if you allow it to pool it can cause odor problems and possibly corrode the pipe if Hydrogen Sulfide is produced.
