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<br />There are three sections where no conclusion as to degradation or aggradation can be made.
<br />Cross Section 2 is immediately downstream from a new rip rapped grade-control structure and
<br />boat chute. The flow over this structure has caused local scour and the building of a middle bar.
<br />Under these changing conditions, no estimate is made. At Cross Sections 39 and 44, the water
<br />is deep and was not sounded in 1996. The first is in the backwater of the Public Service
<br />Company's inflatable rubber dam at the Zuni plant The latter is between two of the drop
<br />structures in the Union Avenue complex of seven drops and boat chutes.
<br />
<br />Cross Sections 49 through 53 at the upstream end of this river study were established only very
<br />recently. It is too soon to decide if the river bed is aggrading or degrading at these spots.
<br />
<br />In addition to the drops at Union Avenue, a number of riprapped grade-control structures with
<br />boat chutes have been constructed across the river to help control the riverbed leveL These are
<br />discussed farther on in the section on Grade-Control Structures.
<br />
<br />In judging the sizes of sediments on the river bed in January 1996, it was found that the low-flow
<br />channel and its margins were often covered with algae (Fig. 5), mostly brown in color, but green
<br />where the flow was faster and shallower. In addition to the algae, where the current was very
<br />low, black organic solids were deposited. In many places, the water was very murky because
<br />of suspended solids floating along. The bed could not be viewed through this water. The term
<br />Urban Veneer was adopted to describe this layer of algae growth and black sediment deposition
<br />on the river bed.
<br />
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<br />Figure 5. A view of Urban Veneer. dead and dying algae and deposited organic sediment.
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