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height and the capacity of tile, ditch alon'J it. 'I'he possibil- ity definitely exists for a major portion of the flood flow to bypass Wiggins to the Wes1: as desl::ribed above. The flood stages in wiggins would be lower than predicted by .the CWCB model, if this possibility occurred. b. The CWCB model star1:e,d just downstream of Interstate 76 (1-76). U.S. Highway 6 (Hwy 6), which has a closure structure, is located only 1:;0 feet upstream of 1-76. The flood stages computed by HEC.-,: at the Hwy 6 closure structure may be sensitive to the start:ing wa.ter surface elevations. It may be better to start tllE:~ model ':l.nother mile downstream, just downstream of u.S. Highway 34, to account for backwater effects from Hwy 34. c. The Corps modified t:he model for this study to rep- resent their modeling practices. Modifications were made with the available informa1:icm, using the same discharges and roughness coefficients as the CWCB model. Corps modifi- cations raised the flood s1:ages only sl.ightly at the BNRR closure location with 0.3 feet for .the la-year flood being the largest. However, flood stages increased 1.7, 0.1, 0.1, and 1.0 feet for the 10-, 50.., 100-, and 500-year floods re- spectively, at the Hwy 6 closure. d. After the corps modifications, .the model still had problems with flow approachinc:r critical depth. These prob- lems could not be resolved due to unfamiliarit:y with the project and insufficient cross sectional data. Therefore the results can only be considen~d approximate. The, results for the CWCB model and the Corps modified model differed most for the la-year flood profile. The Corps modified model had stage increases as high as 1.9 feet for the la-year flood profile. The la-year flood stages were still lower than the two closure structure's invert:s though. The Corps modified model had stage increases as high as 0.8 foot for the lOa-year flood profile. However, stage increases at the clo- sure structures were insignificant for the lOa-year flood. e. There, is concern that the BNRR overflow section may not function properly for th,'~ lOa-year flood, assuming all of the lOa-year discharge of 49,300 cfs passes through the project. Ove,r 50% of the flow would have to diverge from the channel, pass over the overflow section, and converge back to the channel within a 2,000 feet reach. Considerable head loss would occur along wi1:h possible erosion problems along the levee,. Also, no erosion protection exists on the downstream side, of the overflow section where the maximum ve- locities occur. This could result in total loss of the BNRR embankment at t:he overflow sl=ct:Lon location. 33