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3 <br /> was given National awards from the American fisheries Society and the Urban Rivers <br /> Restoration in 1996. If the perception was that the W-weir is a dangerous boating structure, <br /> wouldn't the city have called for its removal? Why weren't all of the W-weirs removed if such a <br /> perceived hazard exists? All of the W-weirs were in the same condition over the last 10 years, <br /> requiring little to no maintenance. <br /> The design objectives, hydraulics of the W-weirs and their performance is quite different than <br /> the "study"reports. I will address the specific topics individually as raised by the Lacey report: <br /> 1. "failing W-structures located in the first phase of improvements": The monitoring of all <br /> the structures,including the W-weirs, do not show them as failing;quite the contrary, <br /> they have been stable for the 10 years of their existence. Other W-weirs that have not <br /> been removed are still in place and stable. The structures are still being used by the <br /> boating public at high flows without incident, as they have for the past 10 years on the <br /> San Juan through downtown Pagosa. The photographs from the Lacey report in Figure 1 <br /> and Figure 2 show the W-weir still intact,even after a 5,000 cfs flood in 1995 had <br /> occurred. One large rock that had come in during the flood is shown in Figure 2 on the <br /> right side of the W-weir structure. If maintenance would have been performed,then this <br /> one, lone rock would have been removed. This would not have necessitated the removal <br /> of the entire structure! Figure B and Figure C of this report show the W-weir at flows of <br /> 1/3 bankfull stage and at bankfull stage,respectively. This structure has remained intact <br /> and has been functioning as these pictures show. The photographs in Figures B and C <br /> will also be referred to in subsequent discussion. <br /> 2. The quote supposedly from my writings that describe "drop,pool,riffle"is not correct. <br /> The bed features below a W-weir create a run,pool, glide feature. A drop is not designed <br /> through either left or right thalweg to prevent a hydraulic jump, causing footer scour and <br /> fish migration problems. The design for W-weirs(Figure 5, Rosgen, 2001)distinctly <br /> shows that the structure invert is at the bed of the channel. A run is a"shooting"flow or <br /> one with high velocity to help route bedload through the structure,as well as route boats <br /> safely through the structure. A drop would be the opposite of the published design <br /> criteria included in Figure 5. The pool below the run is deep, yet of lower gradient and <br /> lower velocity. If a boater tips over in the run,the flows shoot the boater into the pool, <br /> where the lower velocity water allows the boater to easily get out of the river. The <br /> photographs of the W-weir structure in Figures A and B show the velocity distribution of <br /> the higher velocity in the two thalwegs and the low velocity region on both banks, even at <br /> high water, <br /> 3. The charge that the"W-weir only considers biological processes"but not"flow-control, <br /> stability,boat passage, safety and aesthetical appeal'is unfounded and incorrect. <br /> • <br /> a. Flow control. The W-weir is a structure designed to redistribute velocity <br /> vectors away from streambanks into the thalweg. The increase in flow into the <br /> thalweg region not only increases the velocity, but also the depth of flow. This is <br /> important for boat passage and sediment transport. Velocity isovels(cross- <br /> channel distribution of vertical velocity profiles) for a W-weir on the San Juan <br /> immediately downstream of the removed W-weir are shown in Figure C (Rosgen, <br />