Abstract
The enterprise of Rice field dam is to install unique drainage devices in the rice fields. It is expected to mitigate peak flow rate from rice fields and to delay it. There are many types of drainage devices. It is nessesary to select a suitable devices for each region. Therefore, the purpose of this paper is to clarify storage function for each devices. We investigated water strage functions by comparison of three drainage devices, a free drainage, a box drainage vertically installed runoff control boards and a standard drainage, by hydraulics experiments and hydraulics simulations of falling water. A free drainage and a box drainage vertically installed runoff control boards are supposed to has a strage function so that they mitigate flood in the rice fields, but a standard drainage is supposed to has no storage function so that it does not mitigate it.
As results, a box drainage vertically installed runoff control boards constantly works as a storage function and a free drainage works so only under the condition of high water depth and wide rice field area. Especially, a box drainage vertically installed runoff control boards decreases by 74% of peak flow rate and delay it for 280 minutes and a free drainage decreases by 44% of peak flow and delay it for 70 minutes under the conditions: total rainfall of 141 mm during one hours, central peaked type and rice field area of 2000m2.
