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I.vl;-::l'2 the storage that is now a multipurpose carryover to flood control in order to better support the flood con- trol function, we would use this model to tell us what the impacts would be. Not only to flood control, but to all other purposes as well-navigation, irrigation, and so on. In the early days, starting back in 1953, these rules that were put together were passed by a coordinating committee. A committee that was organized at the request of the then Division Engineer. It was made up of state agency representatives and interested federal agencies. They met twice annually, similar to the pub- lic meetings that we now have, to discuss the annual operating plan, or the way they felt the reservoirs ought to be operated. The. Chief of the Reservoir Con- trol Center also served as chairman of the group. It was disbanded in 1981 and public meetings have been held since 1982. That group did function for nearly thirty years. I would like to talk about each of the functions and just make a few comments on how we support and decide how to help each of the functions that we serve. I will start with flood control. These are not neces- sarily in an order of priority nor are they alphabetized. Flood control is the only function that requires evac- uated storage, so we discuss that one first. Chet made a really good presentation back at our public meeting in October explaining that we still have flood prob- lems, but they are not like the flood problems we ex- perienced years ago in 1881 or 1927, or this photo that was taken at the airport in Omaha in 1943, or 1952, which is commonly referred to. You have probably seen this picture before where they were building flash- boards on the flood wall in downtown Omaha to pre- vent the 1952 flood from overtopping the flood wall and flooding downtown Omaha. These kinds of floods have been eliminated. We've not eliminated some of the floods like the one that occurred in 1984. This is a tributary to the Platte, Salt Creek. Over on the Missouri River, just upstrcam from there above the Platte, is Offutt Air Force Base. Vou can see a runway at Offutt in the upper right. You can also see the farmland that has heen flooded, and the flooded cabins along the Missouri down in the lower part of the picture. That was the most devastating flood we've had since 1952. This drawing is put together to demonstrate the difference in flows that we had upstream and down. stream. The width of the river shown reflects the amount of water that was in the river. We were re- leasing 10,000 cubic feet per second (cfs) from Gavins Point when we had 103,000 cfs at Sioux City. The river grew to 115,00 cfs at Omaha, 180,000 at Nebraska City, almost 200,000 at St. Joseph and 250,000 at Kansas City. So we had tributary contributions that were tre- mendous. This was the second year of large tributary runoffs downstream. 1983 was also very large. 1986 and 1987 have had higher than normal contributions by tributaries downstream, but not of the magnitude that we had in 1983 and 1984. The stages were reduced on the Missouri River by 7 feet at Sioux City, 6 feet at Omaha and 4 feet at Nebraska City as a result of our operation of the res- ervoirs. We determine that by the amount of water that was going into storage as well as the amount of water that was flowing past each of these points, using a rating curve to estimate, or a staged discharge re- lation to estimate what the stage would have been if the reservoirs hadn't been in place. That sevcn foot reduction at Sioux City occurred at a time when water was about mop board deep through the marina, which you will probably bear a little bit ahout this afternoon. Not all floods are that dramatic. There are situa- lions that cause difficulties for people. This is a picture that was taken just west of Hamburg. Some wet fields are very wet due to rainfall. Notice the river in the upper left is very high, the overbank areas are wet and the high water on the river side prevents drainage from the protected side of the levee. This has been a com- mon problem in both the fall of 1986 and then again in early 1987. I show a bar chart (Figure 3) of the damages prevented to demonstrate that some years we have very large damages prevented. That is, the system is credited with having reduced damages along the river by large amounts. Other years like 1977, we had none and again in 1981 hecause there were no signif- icant floods or no flows that. would have created any flooding. We determin. the damage that is prevented. That is actually done in .John Velehradsky's shop. Once we tell him how much the stages have been re- duced, they have a relationship between the damage that occurs at given stages and determine how much damage was actually prevented. The bulk of the damage in 1987, the damage pre- vented that is, was the result of elimination of urban flooding. Areas like Sioux City, Omaha, Council Bluffs, and so on received no damage because of the combination of levees, floodwalls and the reservoirs. When the flood walls and the reservoirs both do their share in preventing the damage, they are shared equally between the two or there are other relation- ships. This includes only that credited to the main stem. There would also be very significant damages prevented credited to the levees and the flood walls. 27