Farmland Conservation at Masuda Land Reclamation National Project

Abstract

In July 1983, the western part of Shimane prefecture was visited by the heaviest rainfall in this area in the history of observation. Maximum daily rainfall of 421 mm and maximum hourly rainfall of 97 mm was recorded. At that time, about 280ha of farmland there were no secondary disasters at all. The reasons why the land could withstand such a record-breaking localized torrential downpour were mainly two preventive programs: 1. Measures to keep a bank from breaking: (1) with a very gentle slope like 1:2.0, the bank can be set in dynamic steadiness and can he made compact. (2) Pipe drain set in a bank every two steps can prevent high pore water pressure in a bank. (3) The slope end can be reinforced by concrete gravity walls or frameworks. (4) A catchment canal set across the upper slope can protect the surface of the slope from erosion.