At present the chech dam for building farmland constructed in loessarea

generally

is designed and checked according to the oppotunity of onetime in 10 year and one time in 30 years respectively

which has been dem-onstrated in practice to be lower and thought as the major reason to causedam bursting.Having been studied

the optimum designed standard of floodis one time in 20 years and one time in 50 to 100 years for designed floodand flood check respectively.On total consumption of money and material

it will save 15-20% of that

compared with the two adjucent standard ofdesigned flood.It is suggested that the major engines of the check dam bedesigned on the standard of one time in 25 years

and checked on one timein 100 to 300 years

if done as this

it would be economical.