After the “5·12” earthquake in Wenchuan,many congeries have occurred beside the bank of the river and cut down the flow area of the river section,leading to water block at upstream.The characteristic of water block caused by congeries with different sizes and shapes was researched through flume experiment.The experiment was carried out for different river bed slopes.It was found that the relative height of water block will increase with the increase of the congeries size and the river bed slope.But the influence effect will drop down when the flow become supercritical flow.An empirical formula was deduced through experimental data fitting to identify the different effect on water block height caused by congeries sizes and river slopes.The physical dynamic difference was analyzed to distinguish the influence on water level block effect in subcritical and supercritical flow condition.
