The most critical shortcomings of these assumptions are 1.The flow of water is considered to be one dimensional but in reality it is three dimensional. 2.Darcy\'s law does not seem to hold good at high hydraulic gradients. Solution The most critical shortcomings of these assumptions are 1.The flow of water is considered to be one dimensional but in reality it is three dimensional. 2.Darcy\'s law does not seem to hold good at high hydraulic gradients..