Needle dam
![A manually operated needle dam-type weir near Revin on the Meuse River, France](/Images/godic/202501/29/Revin_Meuse_weir_20041230-_0240922.jpg")
![Needle dam in the Reuss River in Lucerne, Switzerland](/Images/godic/202501/29/Reuss_River_needle_dam0922.jpg")
![Needle dam near Louisa, KY in the United States](/Images/godic/202501/29/Needle_dam_louisa_ky0922.jpg")
A needle dam is a weir designed to maintain the level or flow of a river through the use of thin "needles" of wood. The needles are leaned against a solid frame and are not intended to be water-tight. Individual needles can be added or removed by hand to constrict the flow of the river, forming a sluice.