We jump to the text


  • Zhongwen
  • 한국어
We extend letterWe make letter standardWe reduce letter
  • FAQs 
  • Read Out Loud/Zoom (Easy Web Browsing) 
  • Site map 
  • Search in the Site
To the sightseeing top
The present position: TopWe conduct a business of the inside of thisIt is discussed rainwater drainage plan of the inside of this
We display page for print

Discussion of rainwater drainage plan

Discussion of rainwater drainage plan in development projects

In conduct of development projects, it is necessary to restrain so that rainwater spillage after development becomes at the same level as development Susumu. About quantity of retention that restraint needs (outflow inhibitory dose), measures such as regulating pondage are necessary in consultation with Internal Water Maintenance Department.

1. Development projects which is targeted for discussion

Development activity, construction of building or large-scale repair, setting of outdoor parking lot
(extended building of discussion, outdoor parking lot, pavement of land)

2. Plottage of development projects needing discussion

1,000 square meters or more
(more than 3,000 square meters of reduction of area requirements → 1,000 square meters or more)

3. Submission of rainwater drainage plan, flow of discussion

Submission of rainwater drainage plan, flow of discussion

  1. Submission, discussion
  2. Instruction, advice
  3. Rainwater outflow restraint
    Setting of facility
  4. Setting completion
    Examination of completion

When we refuse instruction, advice

  1. Refusal
  2. Advice
  3. Publication such as Full Name

4. Calculation (rainwater drainage technology standard) of rainwater outflow inhibitory dose in development projects

We retain differences between development Susumu and rainwater spillage after development (for one hour) (adjustment capacity)
A. Development projects more than 3,000 square meters…Adjustment capacity = outflow inhibitory dose
i. Development projects less than 1,000 square meters - 3,000 square meters
  …Adjustment capacity X 1/2 (relaxation rate (※ note)) = outflow inhibitory dose
※Note relaxation rate is provisional measures. In addition, we can put pdfin the sewer junction area (Portable Document Format: 1,020 kbytes)
It is not applied to development projects less than 1,000 square meters - 3,000 square meters.


Civil Engineering Division Internal Water Maintenance Department
Phone number 076-220-2341
FAX number: 076-220-2476

Help us to improve this website by submitting your impression on the site.