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\ , analysis was performed to quantify out-of-bank flows in streets and a revised profile, based on a smaller flow in the channel (with the remaining flow being out of bank), was prepared. This analysis permitted a benefit/cost study of proposed channel improvements for Montrose Arroyo. When the Gingery plan was complete, there was no need for changes to designations for Ceda~ Creek or Dry Cedar Creek. In the case of Montrose Arroyo the Qecision was made to leave the Hydro-Triad delineation designat~d since it was more conservative than the Gingery delineation. The work On the two Flood I~surance Studies was begun in 1978. preliminary F.I.S. report~, and revisions to them, were prepared in 1983. Changes were ~ade to all three stream delineations. On Cedar Creek the contractor stated that, to the best of his recollection, the Hydro-TriaQ/Gingery profile and delineations could not be proved or disproved. For budget reasons i~ was decided not to pr.pare a revised profile. Instead the old delineation was shown as an approximate floodplain with no accompanying profile. The fa~t that a Gibson's store and its parking lot are in one of the ov.rflow areas of the floodplain is one good reason for detailed delineation. I suggest that in view of our roles in supervising both previous studies and in \ designating the Hydro-Triad study, nO designation of approximate ~ floodplain information on Cedar Creek be recommended. Instead the existing designation should ~emain in effect and FEMA should be strongly encouraged to use that information as detailed information. On Montrose Arroyo the contractor used Gingery's information. Unfortunately the Gingery study did not include a profile for the portion of Montrose Arroyo downstream of North 8th Street to its confluence with Cedar Creek. Again the choice was made to provide an approximate delineation for that portion of Montrose Arroyo (about 1/2 mile) instead of extending the Gingery profile downstream. In addition, some of the out-of-bank flow was shown as stopping at the point where Gingery's mapping ended, rather than continuing downstream toward Cedar Creek or Uncompahgre River. Also the out-of-bank flow was delineated as B-zone (500-yearfloodplain) because it was lOa-year flooding that was shallow enough by FEMA guidelines. In other words, even though the areas would currently be subject to laO-year flooding, flood insurance would not be required. Although the F.I.S. for Montrose County indicates that changes were made to the Hydro-Triad profile for Montrose Arroyo, no differences were discernible for that unincorporated area when I compared the two profiles. The delineations are very close also. ) -2-