Tweak salt front animation

[cnell-usgs]

TO DO

• add Philly for better context

Brian Pellerin says..."RE Salt front figure: Could you put Philadelphia or Drinking Water Intakes on the first map for context? You put "Drinking Water Intakes" in the second map, but mention it during the section before.

• research impact of rising sea level on philly drinking water intake

Brian Pellerin says..."Rising sea levels": "Sea level rise is expected to push the salt front further upstream. With just 3 feet of sea level rise, the salt front is predicted to travel once again within the reaches of Philadelphia and threaten fresh water supplies." Is it true that 3 ft will threaten Philly? We should be sure.

• Make Road Salt section appear without delay

DONE

• make map bigger
• include some sort of scaling to indicate how many miles the salt front is moving
• add additional view, possibly scroll triggered, that shows the record high of salt fornt to draw connection between intra-annual variation, sea level rise, and threat to human drinking water intakes

[cnell-usgs]

Here DOI-USGS/delaware-basin-story#90 a new view is set up for the salt front animation. This needs more thought, but the idea is to go from:

1. natural movement of the salt front to
2. predicted salt front position at 1, 2, and 3 ft sea level rise. Sea level rise markers are drawn on, and the salt front movement moves upstream within that range.
3. The predicted upstream movement threatens human uses and when coupled with drought can be higher than that. Draw on drinking water intakes and Philadelphia, remove seal level rise markers, indicate record drought position?

[cnell-usgs]

The salt front animation has been modified to use clip-path rather than animationMotion to be able to use a color fill to represent the salt front, and open up annotation space for the planned changes. The animation movement is based on monthly medians for the salt front position (https://www.state.nj.us/drbc/hydrological/river/salt-front.html). DOI-USGS/delaware-basin-story#94

Moving forward, I'd like to:

• rotate the edge of the clip-path to be perpendicular to river
• add opacity gradient to the salt front so it is not so clearly defined. Possible options to explore for this are (a) to animate offset within a linearGradient or (b) animate an opacity mask position

[cnell-usgs]

This is what it would look like with the gradient animated. Needs some refinement, but wondering what you think @jread-usgs @ellenbechtel @aappling-usgs ?

[jordansread]

Looks like a great update to me!

[aappling-usgs]

Yep, love it!

[cnell-usgs]

Left to do:

• fix bug with mobile breakpoint that makes the map disappear on small screens

[cnell-usgs]

Following up on data source for sea lvel rise predictions. This info is sourced from here:
https://www.state.nj.us/drbc/library/documents/shallcross_saltfront_CDRWforum_oct2019.pdf

The original source is unclear, following up with DRBC contact on that