**2. Types and causes of floods**

Depending on where they occur, floods can be classified into different types as: watershed, riverine, urban, coastal, and glacial. These different types of floods have different spatial scales. For example, glacial outburst cause flooding at a local level but can be more extensive if the dam is broken. Coastal flooding are confined to coastal areas and can wipe out beaches and damage wetlands and vegetation by bringing in salt sea water. Flooding is quite common in urban areas these days, because urban areas turn pervious areas into impervious areas which do not infiltrate rainwater. The different types of floods are caused by extreme rainfall, hurricanes, tides, combined rainfall and snowmelt, improper drainage, improper watershed management, dam/levee breaching, or glacial outbursts. The ubiquitous cause is extreme rainfall, but rainfall and snowmelt together are also a common cause, especially in areas where snowfall is extensive as in the United States.

Likewise, in monsoon climate countries in Asia, destructive floods occur each year massive investments made in flood defenses notwithstanding. In China, damages caused by floods have been over US\$200 billion per decade. Floods during the monsoon season have been commonplace in the Yangtze and its tributaries.

### **3. Flood management**

It is accepted that floods cannot be entirely eliminated because nature cannot be fully controlled, but they can be managed so that the damages caused by them are mitigated. Thus, flood management involves two aspects: technical and nontechnical. Technical aspects are primarily engineering, including hydrometeorologic, hydrologic, hydraulic, geotechnical, and structural; and nontechnical aspects are education, socio-economic, political, legal, communication, internet, and administrative.
