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.' . -,,", '-) l-' ,.J . '- ._~____~_._._n._.._. _<">.____ . . On~n oJ,;. Reaches 1 and 3 have one main channel and as shown in the above tab- ulation, there bas been a major decrease in open channel widths between 1938 and 1971. These two reaches have now grown up in many islands of good vegetative growth with a present open channel width of around 1,000 to 1,100' feet compared to the 1938 width of 2,000 to, 3,000 feet. In 'reaches 2 and 4, the Platte River divided into a major south channel and a smaller north channel. The major south, channel is now about 1,000 to 1,200 feet wide, which ' compares favor- ably with the 1938 open channel. The north channel in reaches 2 and 4 has changed with a large increase in vegetative growth, but ,this channel appears to be carrying less and less of its portion of the total river discharge. The 1977 photographs showed widths simi- lar to those on the 1971 aerial photographs. , Brid~e Restrictions The size of the bridge openings on the Platte River in this reach .has had ,its influence on the width of open channel. Table 1 sum- marizes the width of the bridges as measured on the 1938 and 1971 aerial photographs. This shows that in 1938, the bridges r~presented a significant restriction in the, width of open channel. The 1938 photographs showed numerous dikes constructed along tne Platte River between Overton and Grand Island that have also contri- buted to a reduction in open channel widths. The diversion dam diverting water to the Kearney Canal located about 1.5 miles down- stream from the Elm Creek bridge has by use of dikes reduced the main channel width of about 3,000 feet down to 700 fe~t. at the diver- sion dam as shown on the 1938 aerial photograph. "