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RMA2 begins with the assumption of a universally flat water surface elevation. Using revision cards and hotstart files, a simulation can. be stepped down to reflect real world conditions. As the simulation is stepped down, the previous solution is used to provide initial guesses to the next solution. If the simulation is stepped down too quickly, the solution is likely to diverge and the model will crash. The time needed for a given step is dependent on a number of factors including the size of the mesh, the speed of the computer, and the relative change in tlowcharacteristics in each step. With a Pill500 processor and 256MB of Ram, . each iteration in a model with 20,000 elements can take up to 3 minutes to process assuming nothing else is running onthe.computer. A total of 1,000 successful iterations may be required to step the model down to a real world condition. During this process, it may become obvious that the mesh has to be refined in someway. If the mesh is altered in any significant way, hotstartfiles cannot be used and the stepdown process nwst be started again using a flat water surface elevation. BABITA T AVAILABILITY On September 15, 1999, ata flow of 287cfs, aerial photographs were flown at a scale of 1 "=600'. The aerial photography included the survey site and the representative reach section described for the fish sampling. Aerial photos were qualitatively used to compare habitat availability in the surveyed study sites to longer sections of the river. The images of the sites were rectified using ground control points and the Imagine software package. These images were then registered in the Surface Modeli!lg Software (SMS) and were used for reference in ~~ating~h~pnite.element mesh. Aerial photography for the IS-Mile Reach. . ~; , .;: were purchased from Mesa County. The county rectified the photo with highly precise UTM coordinates. The IS-Mile Reach photographs were taken on September30 and October 1, 1997 at a flow of3000 cfs. 26