Runoff control structures

ENTRY DATE: 19.11.2013 | LAST UPDATE: 19.11.2013

CATEGORIES:

  • Water Resources
  • Runoff control

TECHNOLOGIES MATURITY:

Applicable immediately

Technology Owners:

Each contractor. For reference, please see members' list on the website of the Association for Rainwater Storage and Infiltration Technology

Needs Address

The need to temporarily control runoff into rivers if climate change results in an increase in heavy rainfall events.

Adaptation effects

A reduction or elimination of flood-caused damage by controlling increases in river flow volumes due to climate change. 

Overview and Features

Run off control structures temporarily store rainfall. When a heavy rainfall event occurs, the volume of runoff into rivers increases dramatically, increasing the danger of flood damage. A water storage design can release the rainwater to the river over a longer period of time. 

Major sites for consideration:

  • Public facilities such as parks, schools, city hall, municipal offices, etc.
  • Single-family homes, housing developments, high-rise residential buildings
  • Large commercial facilities (e.g., supermarket parking lots in suburban areas)

Types:

  • Excavation type: The water storage area is excavated to create a water storage area.
    Example: Excavate the ground surface of a park deeper than the surrounding area to create water storage capacity. During regular times it can be used as a playing field or playground. When holding water it functions as an excavated pond. 
  • Berm type: Create water storage capacity by building a low berm around the water storage area.
    Example: A low berm was constructed around the perimeter of a school ground, creating a basin.

    Left photo shows normal conditions, right photo shows water storage.
    Source: http://www.arsit.or.jp/
  • Pilotis type: Build buildings on pillars or pilotis, creating a water storage space below.
    Example: A gymnasium is built on pillars, creating space on the ground level for vehicle parking, and for water storage. 

Cost

Initial costs:

  • Initial costs vary greatly depending on the size of the storage area and materials used.

Subsidy programs:

  • In Japan, legislation provides tax incentives, and low-interest financing is available from the Development Bank of Japan.

Energy source

None required

Ease of maintenance

Cleaning is required after release of stored water, as the storage area, drainage channels and orifices can become blocked by a buildup of soil and debris. One solution is to build a pit to remove debris upstream of the storage area, and to install a screen at the outflow point. 

Considerations

Technicians from consulting and construction firms are required at the design and construction phases.

Co-benefit, suitability for developing countries

This technology is accessible to developing countries, as runoff control structures can be built to store rainwater using the local terrain in its natural form, without the need for materials such as concrete. 

Information Resources

Association for Rainwater Storage and Infiltration Technology 
Introduces a variety of rainwater storage and infiltration designs (in Japanese only).
http://www.arsit.or.jp/