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<br />expensive ($2.100 pcr river km). high-resolution L1DAR sensor. which provided 17-cm vertical <br />accuracy on bare ground. is also being evaluated and may provide an acceptablc medium. <br /> <br />4.0 Physical Resources <br /> <br />The physical resourccs program provides information and assessments of dynamic <br />hydrologic and geomorphic processes rcsulting from Glen Canyon Dam operations that directly <br />and indirectly affect the CRE. The overall objective of the program is ecosystem sustainability of <br />hydrologic and geomorphic processes and interactions and long-tcrm conservation of sediment in <br />main-stem and riparian environments. The habitats of concern include channcl environments <br />(cobble and gravel bars. dcbris fans. and talus shorelines) where benthic organisms occur and <br />which are used by spawning fish; aquatic near-shore habitats (sandy shorelines and backwaters) <br />that are used by juvenile native fish and that provide substrates for plants; terrestrial habitats that <br />support riparian Ilora and fauna; terrestrial substrates used by recreational visitors; and terrestrial <br />substrates that support and preserve cultural resources up to the stage associated with pre-dam <br />river terraces. This overall objcctive is being approached by three program clements, which also <br />have implications for biological and cultural resources. <br /> <br />I. Long-ternl monitoring of line-grained sediments in key storage settings documenting <br />system-wide changes in these deposits (morphology, volume, area distribution, <br />and grain-size characteristics) relative to dam operations and natural tributary <br />inputs. <br /> <br />2. Long-tern] monitoring and evaluation of coarse-grained sediment inputs (with respect <br />to volume. grain-size. and topographic changes within debris fans, eddics. cobble <br />bars, and the channel suhstrate) from tributary debris tlows and Glen Canyon <br />Dam operations relative to system-wide. coarse-sediment mass balance and <br />distributions of aquatic and terrestrial habitats. <br /> <br />3. Developing or refiniug existing stream-tlow and suspended-sediment transport models, <br />considering a subset of river reaches grouped by their common characteristics <br />and behavior. to better predict average sand-bar deposition and erosion responses <br />to varied discharge rates, fine-grained sediment supply, and thermal conditions, <br />and to better understand coupled suspended-sediment and strcam-tlow processes <br />along the main channel. <br /> <br />Grain size is an important paramcler, especially with respecH9 the 10 lowest size classes <br />within the sand, silt, and clay categories. However, these fine grain sizes are also the most <br />difficult to detect with remote sensing due to the small size of the particles. Past monitoring <br />within this program concentrated on just 4-5 reaches within the first 100 river miles, on the <br />assumption that these sites adequately represented corridor changes from dam operations. <br />Monitoring within this program has now becn expanded to 1\ reachcs that are distributed <br />throughout 230 miles of the corridor. As in the biologic resource program, the parameters that <br />are monitored by the physical resource program can be separated into two catcgories: aquatic and <br />terrestrial. <br /> <br />4./ Aquatic Environment <br /> <br />Unlike the biologic resource program, the physical resource program is concerned mainly <br />with thc inorganic (geologic) components within the aquatic environment, which are easier to <br />detect and monitor using remote-sensing data. <br /> <br />18 <br />