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Draft Final Completion Report [0 UDWR for Contract #93-1070, Amendment 3 36 deposited on the river left side of the secondary channel at the downstream end of the bar. The bank-attached bar became emergent between the June 22 and August 15 surveys. During this period, only small changes in morphology were measured on the top of the bank-attached bar. The thalweg filled at all cross-sections within this subreach. The bar shoulders, which are the submerged bars between the emergent point or bank-attached bar and the thalweg, were eroded throughout the reach. During the base flow period of summer and fall 1993, the thalweg in the study reach continued to fill and erosion occurred on the bar shoulders. The bank-attached bar was reduced by 0.1 to 0.2 m during this period at cross- section 8 (Appendix C), possibly by the high winds observed during this period and which are common (Andrews and Nelson. 1989). 1993 Emer2ent bar form After flood recession. the eri1ergent bar was very different in form from the previous year. The net aggradation of tte bar measured during the 1993 field season was approximately 0.5 m in the secondary channel, and between 0.5 and 1.0 m on the surface of the bar platform. The chute channels that formerly had crossed the upstream portion of the bar in 1992 no longer existed. Although the vegetated area upstream of cross-section 8 scoured sufficiently to remove existing vegetation (compare Fig. 8 and Fig. 17a), the saltcedar and willows were not removed from the downstream vegetated area just upstream from cross-section 7. The area of the bar above 95.0 m increased from 0 to 3540 m2. Krider (1994) analyzed the sedimentary structures of the newly aggraded bar. He showed that the bar platform and secondary channel aggraded at least 0.3 m, with aggradation occurring by deposition of low-amplitude (0.1 to 0.2 m) migrating dunes at high flows, and by deposition of climbing ripples during the descending limb of the hydrograph. The downstream and lateral increases in bar extent were accommodated by the advance of slipfaces. These slipfaces had heights up to 1 m in some locations and were formed with sediment supplied from downstream-migrating dunes on the bar platform. 1994 - O:mnel cross-section measurements Overwinter flows eroded the downstream end of the bar (near cross-section 7), and small mid-channel bars became emergent near cross-sections 7 and 10. The location of the thalweg migrated from river left to the bar margin in the vicinity of cross-sections 9 and 10 during this period.