Floods Week 4

Questions for Homework & Discussion  Would you live in a flood-prone area?)  What level of risk from flooding is acceptable to you?  How would you know if the flood risk was assessed accurately?  What should be done to prepare for the hazard and prevent catastrophe?  Would you live in a flood-prone area?)  What level of risk from flooding is acceptable to you?  How would you know if the flood risk was assessed accurately?  What should be done to prepare for the hazard and prevent catastrophe?

Questions to consider  What causes the flood hazard to vary?  What is the impact of climate change on the flood hazard?  The five concepts from Chapter 1  What are the types of flooding?

Causes of Flooding  Heavy rainfall  rate of rainfall exceeds infiltration capacity of soil  Heavy rainfall  rate of rainfall exceeds infiltration capacity of soil

Drainage Basin  area contributing to river  drainage density  soil permeability  relief  area contributing to river  drainage density  soil permeability  relief

Floodplain  flat area next to a river  area subject to flooding  stores flood water  flat area next to a river  area subject to flooding  stores flood water

Hazards  Flooding  Sedimentation  Erosion  Flooding  Sedimentation  Erosion  Transportation disruption  Disease  Displacement  Agricultural losses

Risk Zones Flooding: Presidential disaster declarations related to flooding Green: one declaration Yellow: two declarations Orange: three declarations Red: four or more

Forecasting Floods

Predicting Floods  Measure rainfall  Model runoff response  Measure rainfall  Model runoff response  drainage basin characteristics  channel characteristics  past events

Response to Flood Hazard  Flood control  dams  retention ponds  levees  channelization  Flood control  dams  retention ponds  levees  channelization

Response to Flood Hazard  Insurance: only through federal government  Zoning  Insurance: only through federal government  Zoning

Human Impact  Increases runoff  pavement  buildings  drainage improvements  Increases stage  levees  bridges  channel alteration  Increases runoff  pavement  buildings  drainage improvements  Increases stage  levees  bridges  channel alteration