Daylighting streams means taking the waterflow out of an underground sewer, and instead turning it back into an above-ground streamflow, reducing how often the sewers overflow and also creating a pretty little stream!!
I say “turning it BACK” into an above-ground stream because very often— almost always— mainline sewers and storm drains follow very closely the historic drainage routes or stream routes in that region. This is because our underground infrastructure generally follows surface topography, and topography has a strong ability to endure despite urban development.
However, things do change— valleys are filled and hills or bumps are leveled over time— and so when you think about daylighting a stream or river, you have to make sure that your idea for a route DOES actually flow downhill the entire way! Also, because the waterflow is CURRENTLY underground, often you have to find a way to keep it flowing downhill even though the place you want to start from might be BELOW the level of the surrounding landscape.
This is the case for Tibbetts Brook in the bronx, which currently heads into a big sewer tunnel from a small lake in Van Cortlandt Park. (It also flows above-ground north of the bronx.)
The most-often-proposed route for daylighting is along the abandoned rail line next to a below-grade highway. I think this is too out-of-the-way, and i’d love to see the brook flowing down the center of Broadway in the bronx— underneath the elevated subway lines— or down Tibbetts Ave a couple blocks west of Broadway. See below for brief comparison of elevation issues/non-issues for both routes.
My proposed route: along Tibbetts Ave and/or along Broadway. See image below for screenshot of map with elevation profile of route along Tibbetts Ave.
1.08 miles, starts from Tibbet and W 240th St
Has 3 “uphill” moments on this profile, but only at 1 foot each time-from 19 to 20 feet, from 19 to 20 feet, and from 14 to 15 feet
Starting elevation approx 24 feet
CURRENTLY PROPOSED ROUTE - along old rail line
Details on this route, taken from reviewing the elevation profile
(when i first made these maps, i used a convenient website that maps your running route, specifically because it automatically showed elevation profiles. Then they updated their website and now I can’t find the elevation profile. Google Earth does offer elevation profile options as well as do some websites using google maps api.)
RAIL LINE ROUTE:
1.51 miles, starts from south edge of Van Cortlandt Lake in this diagram, at elevation of 20 feet (currently water flows out view flume in a north-west direction from this end of the lake, so this is changing the route of the water slightly.)
NOTE: there is currently some elevation RISE in all directions from Van Cortlandt Lake, approx from 20 feet altitude at lake to about 30 feet at Broadway (west edge of park) and along south edge of park. However, this elevation map might be inaccurate, as the old rail line follows a valley from park and to the Major Deegan.
[Note: review this area via walking and determine if actual land is downsloping. Elevation here could be from LIDAR data which would generalize the elevation after measurements of the tops of trees, and might not have included valley area.]