Flood management planning and design of flood control facilities has evolved in recent years. Today, management of floods include planning and construction of facilities such as dams and detention facilities, coordinated operations of the reservoirs with flood control reservations, improvement of flood channels and levees, watershed management and proper land use planning. Flood control refers to all methods used to reduce or prevent the detrimental effects of flood waters. Floods are caused by many factors: heavy rainfall, highly accelerated snowmelt, severe winds over water, unusual high tides, tsunamis, or failure of dams, levees, retention ponds, or other structures that retained the water. Flooding can be exacerbated by increased amounts of impervious surface or by other natural hazards such as wildfires, which reduce the supply of vegetation that can absorb rainfall.