浸透型流出抑制施設の動向と今後の課題

抄録

In Japan, urbanization on river basins is very rapid, especially in the three megalopolitan areas (Tokyo, Osaka, Nagoya). Along with the urgent river improvement works, run-off control facilities are needed in such basins.
Run-off control facilities are classified into two types, detention type and infiltration one, according to its form and function. The history of run-off control faciliti es started from the storm water detention pond. Recently application of infiltration type facilities is increasing mainly in and around the Tokyo Megalopolitan area.
The study on storm water infiltration facility has p r ogressed since the infiltration ability of the Kanto loam layer was proved larger than expected. It is expected that infiltration facilities such as infiltration pit, trench and permeable pavement are useful for onsite treatment of storm water.
Comparing the detention-typ e facility with the infiltration-type one from the viewpoint of run-off control, the former makes the runoff peak delayed and flat, and the latter has a basic function to cut the bottom part of the run-off. Infiltration-type facility is thought to be useful not only for run-off control but also for recharging groundwater. Thus it has a role to restore the hydrological circulation weakened by urbanization.
From the viewpoint of flood control plan, techn i c a l subjects on the storm water infiltration facility, which are described below still remain.
(1) Simple survey method for defining the infiltration ability of the ground
(2) Estimation method of the infiltration ability of infiltration facilities
(3) The influence of the facility on surrounding environment
(4) Estimation method of the run-off control effect
Infiltration type run-off control facilities a re used on a small scale and dispersively.