International Conference on Rain Water Cistern Systems
"Rainwater Catchment for Future Generations"
Keelung, Taiwan, R.O.C. - August 1991
9: Alternative Uses of Cistern Water
A Simple Weir for Economical
Research Institute of Forests and Rangelands, Iran.
Diversion dams or weirs sometimes constitute the most expensive and troublesome
structures in the design and construction of floodwater spreading (FWS) systems.
Many plan for construction of potentially viable FWS systems have bee cancelled
in the feasibility stage studies because, on occasions, the expenses involved
in the design and construction o a single weir or diversion dam far outweigh the
cost of the rest of the project. Thus, justification of the entire project hinges
on designing a workable structure at a low cost. Gabion provides a useful material
for construction of simple, inexpensive weirs which could be fitted into many
designs, and may be. built by unskilled laborers.
Fifteen pieces of 3 0 x 4 0 m, 3 mm diameter galvanized wire netting were used.
to construct a.0.60 m high on a 28.0 m wide ephemeral river on a debris cone to
diver up to 5m3 s-l of floodwater to a 25 ha FWS system in the Gareh Bygone Plain
in, southern Iran. The costs were at least 136 times lower than building a hydraulically
efficient, concrete structure having the same capacity.
Although the intake structure behind the weir located on the inside of the
river bend, and at a 9° angle to it, no detectable deposition of sediments
has--taken-place at this point during 6 years of operation. These hydraulic anomalies
deserve further attention.
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