Dogwood Valley Rd down to Watts Bar Lake: two tiles of Tennessee's 2.5 ft lidar, 737 to 1,185 ft, 10 ft contours (bold every 50 ft), parcel lines from Tennessee Property Boundaries, home in red. Tap anywhere to read the ground and the parcel it is in.
Press Rain and the storm falls on every cell of a 10 ft grid read from the same lidar. Each cell takes in what its soil can drink — the USDA survey's hydrologic group, slowed under roofs and pavement in the land cover — and the rest runs to whichever neighbours sit lower, pooling in the sinkholes this karst is full of and following the hollows down to the lake. The cloud rains on one spot while you hold it, so you can trace where a roof or a field drains. The faint blue lines are the drainage the lidar itself implies: every pixel of the 1 m model, pit-filled, and the land draining through it counted.
It is a cartoon, not an engineering model: the water has no momentum, the ground does not fill up, and the depths are exaggerated so a thin sheet still shows. Where it goes is honest; how deep it stands is not.
| 1-yr | 2-yr | 5-yr | 10-yr | 25-yr | 50-yr | 100-yr | 200-yr | 500-yr | 1000-yr | |
|---|---|---|---|---|---|---|---|---|---|---|
| 5-min | 0.34 | 0.40 | 0.47 | 0.53 | 0.62 | 0.69 | 0.77 | 0.84 | 0.94 | 1.03 |
| 10-min | 0.54 | 0.64 | 0.75 | 0.85 | 0.99 | 1.10 | 1.22 | 1.33 | 1.49 | 1.63 |
| 15-min | 0.68 | 0.80 | 0.94 | 1.08 | 1.25 | 1.40 | 1.54 | 1.68 | 1.88 | 2.04 |
| 30-min | 0.93 | 1.10 | 1.34 | 1.56 | 1.85 | 2.10 | 2.36 | 2.62 | 2.99 | 3.31 |
| 60-min | 1.16 | 1.38 | 1.72 | 2.04 | 2.46 | 2.85 | 3.24 | 3.67 | 4.29 | 4.83 |
| 2-hr | 1.37 | 1.63 | 2.01 | 2.39 | 2.89 | 3.34 | 3.81 | 4.32 | 5.05 | 5.70 |
| 3-hr | 1.48 | 1.76 | 2.16 | 2.55 | 3.07 | 3.55 | 4.04 | 4.57 | 5.32 | 6.00 |
| 6-hr | 1.84 | 2.17 | 2.62 | 3.07 | 3.67 | 4.21 | 4.76 | 5.36 | 6.20 | 6.95 |
| 12-hr | 2.29 | 2.70 | 3.24 | 3.77 | 4.46 | 5.07 | 5.68 | 6.34 | 7.22 | 7.99 |
| 24-hr | 2.80 | 3.35 | 4.08 | 4.66 | 5.45 | 6.08 | 6.72 | 7.37 | 8.25 | 8.94 |