Backwater effects on wave propagation are investigated experimentally and theoretically for various initial water depths, by discharging different inflow hydrographs into a rectangular channel. The wave is induced by a constituted inflow tank. Water depths are measured both in the tank and in three sections along the channel by means of a computerized recording system, consisting of conductivity type probes, a simple voltage divider circuit and a data acquisition card. Experiments are realized for five typical inflow hydrographs. Explicit and implicit finite differences approaches are used for numerical analysis to extract the pattern of wave peak variation by time and flow section. In consequences of experimental and theoretical analysis, wave attenuation mechanism is discussed depending on initial water depth and shape of the inflow hydrograph supplied. (C) 2009 Elsevier Ltd. All rights reserved.