Modelling River Flow

From early experiences of dropping sticks into a river and watching their passage downstream, or later it becomes evident that the speed at which the water flows may vary considerably across its width. For a straight stretch of river the flow will usually be fastest in the middle and tail away to almost zero at the banks, whilst on a bend the speed of flow is usually at its highest near the outside of the bend, where it erodes the bank, and slowest on the inside of the bend, where it builds up deposits. Experienced boatmen use this knowledge to their advantage, taking the fast water when going downstream and seeking out the slow water when travelling upstream. Water authorities, too, need to have specialised knowledge of a river's crosssection and flow pattern to be able to make accurate estimates of the volume flow of water.