Cobb streams: official vs lidar (5 ac)

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In the traced area

After hiding lines in lakes and reservoirs, lidar (5-acre cutoff) matches 83% of official stream miles within 20 m (about 65 ft). 55% of lidar miles (about 909 of 1,665) are not on the official map. The traced area is 18 of 26 watersheds, about 54% of the county. Unmasked: 82% match, 59% excess of 1,852 lidar miles.

Layers

Stream buffers (estimate) Blue buffers Blue lidar lines Show confidence (dashed = less certain)

Darker band is the 50 ft buffer; lighter band is the 25 ft setback. Uncheck Blue buffers to see the amber version. Estimate only, needs a survey; existing homes may be grandfathered.

When Blue lidar lines is on, lidar channels are one stream blue; official Cobb streams are a darker, thinner navy so they stay distinct. Uncheck it to get the orange / red / yellow colors back.

Confident (near a mapped stream, or larger drainage) Less certain — verify in field (small lidar-only channels, bridges, map fills)

Applies to the 3 ac cutoff in the Willeo test area and in Fulton (Proctor Creek / Lois Place). Less-certain reaches get a lighter buffer. Countywide Cobb 3 ac can be added later.

Lidar cutoff

Official Cobb streams Lidar 5 ac (near official) Lidar only (not on official map) Lidar 3 ac (test area, near official) Lidar 3 ac only (test area) Gap-closed lines (test area)

Yellow ticks are culvert bridges (≤60 m). Dotted blue lines are filled from Cobb’s official map where lidar missed a stretch.

Bridged gaps (≤60 m) Filled from county map (lidar miss) 3 ac test section (Willeo Creek) Water bodies (lakes, ponds, reservoirs) Show lidar lines in water Official streams outside traced area Federal stream map (NHD) Traced-area boundary Untraced area mask

Fulton County — Lois Place

Lidar lines in the Proctor Creek watershed, compared with the federal stream map. Research preview; estimates, survey required.

Fulton lidar cutoff

Fulton lidar (near federal streams) Fulton lidar only (not on federal map) Fulton gap-closed lines

Yellow ticks are culvert bridges (≤60 m). Dotted lines are filled from the federal stream map where lidar missed a stretch.

Fulton bridged gaps (≤60 m) Filled from federal stream map Federal stream map in Fulton Lois Place survey creek Proctor Creek watershed Fulton County outline Fulton 5 ac, whole county (simplified)

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