most widely used hydraulic structures as flow measuring and flow control devices in open Channels.
Conventional rectangular, triangular, and trapezoidal weirs are among the oldest weirs. The concern of this
paper is to study the effect of height and surface roughness(that coming from different of construction
materials)of crump weirs on discharge coefficients (Cd) under different flow conditions.
This work was conducted in experimental flume by using three sizes of crump weir and three
types of surface roughness. The obtained results show that Cd values will increase with increasing flow rate
as well as with decreasing in crump height; an increase in surface roughness of crump weir can makes great
reduction in Cd value. (The water level to weir height) h/P effect on Cd values increase with increasing in
crump weir height. An empirical relation was obtained to estimate the coefficient of discharge Cd under
different height and surface roughness of crump weirs.
Key words: weir, roughness, surface, flow.