SYSTEM: Urban flooding as a planning system

1. System name: Urban flooding management system

2. Brief description:

The design of cities takes into account some measures for drainage of rainwater, often in open or underground spillovers that carry water to natural waterways/rivers, or some cases, into sewer lines. As climate is changing and when rainfall becomes more intense, drainage systems are often inadequate resulting in urban flooding.

3. Current constraints (factors of production etc):

• Drainage channels designed with a maximum flow in mind

• In some cases, no consideration was given to drainage of excess rainwater, especially in unplanned settled areas

• Densely settled areas make it hard or impossible to install or modify drainage channels

• Old drainage systems expensive to upgrade or repair

4. Risks now and in the future (CC and others):

• Risk of flooding locally during heavy rainstorms

• Risk of failure of older drainage lines/blockages leaving to backflows and flooding

• Risk of levees failing and causing flooding

• Risk of dams failing and causing flooding downriver/dams overflowing and gates having to be reopened urgently, leaving to flooding

• Risk of loss of life when people unfamiliar with flood waters take chances in crossing overflowing bridges, etc

• Risk of flooding in human settlements/houses and business areas

• Risk of drainage system failure contaminating drinking water systems

• For cities at mouth of major river systems (coastal cities), risk of heavy rain in any arts of the watershed leaving to flooding downriver in the city

5. Adaptation options to address the CC risks:

• Upgrade old drainage systems and expand capacity

• Build underground storm water storage areas (e.g. water storage under the Washington Mall, in Washington DC, USA; Bangkok City) and optionally pumps to redirect water to alternative outlets (e.g. Tokyo example)

• Upgrade flow channels to re-direct storm water to parks in the city (e.g. Copenhagen)

• Redirect river flows towards coastal cities to alternative channels into the sea to reduce flooding (e.g. Nadi, Fiji)

• Slow down river flows with dams or other structures along the river, to reduce flooding in coastal cities

• Build levees

• Build walls around important infrastructure (e.g. around a museum)

• Builds walls around coastal cities (NY – xxx)

6. Required other actions to ensure adaptation is successful (e.g. baseline development investments, etc):

• Enforce zoning laws for city dwellings to avoid flooding damage of houses

• Develop evacuation plans and conduct drills

• Plan cities to include soakways, directed drainage channels, etc

7. Adaptation potential rating

• Medium?