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A laboratory study was conducted on stepped and unstepped weirs in order to find their efficiency of dissipating flow energy. Thirty six weirs were constructed and tested to compare between stepped and unstepped weirs in flow energy dissipation, twenty seven of them were stepped while the rest were unstepped. Three heights of stepped weirs (P=36,45,54)cm were used with different numbers of steps (n=9,12,15) , and three downstream slopes of stepped face (h/l=1/2,1/3,1/4) were tested, while for unstepped weirs one height of weir (P=54)cm and three downstream slops (=26.6 o ,18.4 o ,14 o) were tested. The results showed that increasing height of weir and decreasing both number of steps and downstream slops stepped face of the weir will cause an increase of the ratio of flow energy dissipation, and the stepped weirs are more efficient in flow energy dissipation compared with unstepped weirs. The percentage of flow energy dissipation (E%) is increased by increasing the ratio of height of weir to critical water depth (P/d c), the ratio of length of the step to critical water depth (l/d c) and the ratio of height of step to critical water depth (h/d c) while it decreases by increasing the discharge (Q). Imperical relationships between the ratio of flow energy dissipation and factors affecting it were obtained in stepped weirs.

The main objective of this study is to investigate the experimentally the coefficient of discharge for three baffle sluice gates and compared with single gate. The channel slope was changed tow times (0, 0.0075). For this purpose three baffle sluice gates were made from fibber class with (1cm) thick, (30cm) wide and (15,25,30)cm height for first, second and third gate respectively. The three gates have been sharp edge from the top and bottom with 2mm thick .The distance between the three parallel baffle gates were changed three times (2, 3.5, 5) cm. The analysis of results showed that discharge coefficient Cd in horizontal channel is larger than its value in inclined channel with direction of flow and the change in space between gates didn ' t cause an important difference between values of discharge coefficient Cd. The values of Cd were between (0.561-0.736) for horizontal channel and three gates, while when the channel inclined the values of Cd were between (0.523-0.662) for three gates.

The aim of this research is to calculate experimentally the coefficient of discharge for cutthroat flume. Nine models were contracted with different angles (α=30°, 45°, 60°), for each angle, Three ratios of width of cutthroat to width of channel B c /B were used (B c /B%=20, 33.3, 50); the slopes of the channel were changed five times (S=0.0, 0.001, 0.002, 0.003, 0.004) for each ratio. The results show that the coefficient of discharge C d increases as the slope S increases, and as the ratio B c /B, is the ratio of head of water through cutthroat to width of cutthroat h c /B c , critical depth through cutthroat to width of cutthroat y c /B c increases, and for a constant ratio B c / / B, C d increases as α increase. An empirical model was predicted to calculate the C d in terms of the perimeters (S, h c /B c , y c /B c , B c /B , , and α), finally the water surface profiles were drawn and there were in a continuous trend.