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Stream channels respond on short time scales to regional events , such as changes in discharge during flooding , and to local changes , including increased runoff from urbanization . Because of their high moisture content , individual components of forest canopies and other vegetative covers ( e.g ., leaves , branches , trunks ) represent discrete scattering and absorbing elements to the microwave power transmitted by imaging radars . For this reason , we strongly endorse a series of projects over the next few years to test the suitability of SAR interferometry for volcano monitoring and to determine requirements for future satellite missions , partly or wholly dedicated to volcano monitoring . Inspect all new plants and their associated soil carefully for the symptoms and signs noted above . Over major portions of the middle and high latitudes , and at high elevations in the tropical latitudes , snow and alpine glaciers are the largest contributors to runoff in rivers and to ground-water recharge . A national SAR program for oceans and ice can be formulated considering the concerns of present-day ocean and atmospheric science , the history of past achievements in SAR ocean observations , the state of development of ocean backscatter and hydrodynamic theory , and the recent instrument advances in SAR engineering . While it may not be possible to do so in all circumstances , the intention is to provide appropriate assistance to staff and to take a positive attitude to making adjustments . Switchgrass stands up in the winter and provides food for birds and cover for wildlife , and can be quite attractive with hoarfrost or ice on the flowers . These teams would be funded to exploit data from both NASA and non-NASA sources , and would be charged with development and testing / validation of new applications , both scientific and commercial in nature . In this chapter , we address how surface deformation data can be used for the very practical benefit of eruption prediction and to address even more fundamental scientific problems bearing on understanding magmatic systems .