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<br />,-: ';; ''')81 <br />";:,)J,,;;,,' , <br /> <br />III. Assertion: The structures impact the flood plain, therefore the Boating Park is not <br />in an appropriate reach of the Yampa River. (McLaughlin at Topics #2, 3, 4; Browning <br />at Paragraph #'8 1-7.) <br /> <br />Rebuttal: The Boating Park structures do not have a negative impact on the flood <br />plain. <br /> <br />My first general comment on the flood impact issue is to note a discrepancy between the <br />reports prepared by Mr. Browning and Mr. McLaughlin. Many of the comments made <br />by Mr. McLaughlin are based on a HEC-RAS study that was supposedly undertaken by <br />Mr. Browning. I have only recently received a copy of this study as it was not provided <br />with the reports and arn undertaking my own modeling analysis at this point. Of note, <br />however, is that Mr. McLaughlin cites this study and model as an "uncalibrated" draft <br />(McLaughlin at "Topic #9") while Mr. Browning, the author of the study and apparent <br />expert in hydraulic modeling and hydrology, cites the study as a final and dispositive <br />analysis concerning the impact of the Boating Park on the flood plain. My preliminary <br />analysis suggests that Mr. McLaughlin's characterization of this model as uncalibrated <br />and a draft is much more accurate. <br /> <br />Mr. McLaughlin states as his basis of opinion that it is "apparent" based on a site visit <br />that the structures constrict and impact the flood conveyance capacity of the Yampa <br />River in the Boating Park. He supports his opinion by reference to a cross-sectional <br />comparison (Figure 1 of his letter report) of a cross-section that he claims is upstream of <br />the D-Hole. This Figure is meaningless and misleading for several reasons: <br /> <br />. The section labeled as "Upstream of the D-Hole" in Mr. McLaughlin's "Figure I" <br />is marked as station 996024. This station is, in fact, downstream of the D-Hole <br />and is far enough outside of the scope of this project that it does not appear on the <br />survey conducted by the CWCB that was referenced in Mr. Browning's letter. <br />. A particular cross-section may create a flood hazard if it cannot convey a similar <br />amount of flow as the unmodified streambed. The conveyance capacity is a <br />function of velocity and area ata cross-section. Simple observation that the river <br /> <br />8 <br />