H flumes are a hybrid between flumes and weirs.  H flumes can measure a wide variety of flows, from very low to extremely high volumes.  H flumes were developed by the US Forest Service as small portable flumes to measure water flow.  The measuring point of the H flume, selected during development, is in the draw down effect, this means that H flumes are very sensitive to slight errors in measuring point position.  A straight uniform approach must be provided that matches the inlet width of the H flume.  H flumes require a non-impeded discharge so that there can be no submergence (backup in the flume).  For more information on monitoring H flumes see the FC200, Open Channel Flow Monitor.