Flooding can affect many areas of the world, whether coastal or inland, and many of the conditions for imaging are the same. Requirements for this application are similar the world over. The SAR data is most useful when integrated with a pre-flood image, to highlight the flood-affected areas, and then presented in a GIS with cadastral and road network information. The land / water interface is quite easily discriminated with SAR data, allowing the flood extent to be delineated and mapped. RADARSAT in particular offers a high turnaround interval, from when the data is acquired by the sensor, to when the image is delivered to the user on the ground. For these reasons, active SAR sensors are particularly valuable for flood monitoring. Flooding conditions are relatively short term and generally occur during inclement weather, so optical sensors, although typically having high information content for this purpose, can not penetrate through the cloud cover to view the flooded region below. Turnaround time is less demanding for those involved in hydrologic modelling, calibration/validation studies, damage assessment and the planning of flood mitigation. Many of these users of remotely sensed data need the information during a crisis and therefore require "near-real time turnaround". The identification and mapping of floodplains, abandoned river channels, and meanders are important for planning and transportation routing. Users of this type of data include flood forecast agencies, hydropower companies, conservation authorities, city planning and emergency response departments, and insurance companies (for flood compensation). ![]() Incorporating remotely sensed data into a GIS allows for quick calculations and assessments of water levels, damage, and areas facing potential flood danger. Remote sensing techniques are used to measure and monitor the areal extent of the flooded areas, to efficiently target rescue efforts and to provide quantifiable estimates of the amount of land and infrastructure affected. Inland floods can result from disruption to natural or man-made dams, catastrophic melting of ice and snow (jökulhlaups in Iceland), rain, river ice jams and / or excessive runoff in the spring. Flooding is necessary to replenish soil fertility by periodically adding nutrients and fine grained sediment however, it can also cause loss of life, temporary destruction of animal habitat and permanent damage to urban and rural infrastructure. A natural phenomenon in the hydrological cycle is flooding.
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