Attributes for Riverscapes with Multiple Channels, etc.

[lauren-herbine]

From @joewheaton in #563:

We need to think about what we actually want from a riverscapes perspective. This is easy for a riverscape where channel centerline exists (and lets not forget many do for NHD+HR). We still have not defined what we want though for a riverscape with multiple channels and channel segments within the riverscape segment. Do we want:

• Attributes of primary anabranch
• Attributes of primary vs. secondary anabranch
• Average of all anabranches
• Average of all channels (anabranches + tributaries + yazoos)
• Max/Min of any of above?

River Styles itself is rather vague in this regard. However, one thing that we're assuming in our discussions here (implicitly) is that we need each attribute calculated for the entire network. River Styles DOES NOT operate that way. It needs certain attributes for certain valley settings... We can play that game too and maybe side-step the ones with difficult or ambiguous calculations as they have already been flagged as something totally different.

[lauren-herbine]

Additional comments on this from @joewheaton in #240

Multi-threaded Use Cases?
It is also worth noting that we don't really play out or clarify how to calculate confinement for a valley bottom segment versus a channel reach segment. We have only really calculated this on drainage networks and we're not clear on whether active channel margins and calculation of confinement is for each anabranch separately or for all anabranches and considered for outermost (i.e. closest to VB margins).