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Water · Select a property, draw a box or polygon, or upload a boundary

Drainage map for your property: where water flows and ponds

This drainage map for your property shows where water flows across the ground in heavy rain and where it will pond once the low spots fill. Channels are drawn as an ordered stream network from the USGS 3DEP lidar model; ponding areas come with depth, area and volume.

It shows the flow paths the terrain itself creates, clipped to your boundary, and exports them as GeoJSON or KML for a drainage designer.

Free to run · pay to download

See the full result on the map free, with no account. Download the drainage channels as GeoJSON or KML with a pass: US$29 for 24 hours, US$99 for 30 days or US$399 for 12 months, a one-off payment in US dollars that never renews. Every download on the site is included while the pass lasts.

Open Water & Drainage on the map →Pass prices and what’s included

Who uses this

  • Landowners. Find where water runs and sits before siting a house, a shop or a driveway.
  • Drainage and landscape designers. Plan swales, French drains and culverts on real flow paths.
  • Farmers and ranchers. See which draws carry the most water and where fields pond.

When to use it

  • Finding where water runs across a property after heavy rain, and which draws carry the most.
  • Locating low spots that will hold water, for drainage design or to avoid siting a building there.
  • Planning culverts, swales and fence crossings.

Tools for your job

Water & Drainage is one step in a bigger question. These are the jobs it helps with, and the tools that go with it.

For the job: Buying a lot or rural acreage

What is the ground like, and how does it compare with the others on my list?

  1. 1.Property — Selects the county taxlot so every other tool is clipped to the boundary.
  2. 2.Property Report — A PDF with contours, slope, aspect, winter sun, drainage and elevation for that one parcel.
  3. 3.Saved Properties — Up to 5 places side by side: elevation, slope, winter sun and drainage.
  4. 4.Water & Drainage (this tool) — Where water will run and pond across the property in heavy rain.

For the job: Drainage, flooding and wet ground

Where does the water go, and where will it sit?

  1. 1.Water & Drainage (this tool) — The drainage channels across an area, and where water ponds once low spots fill.
  2. 2.Wetness Map — Which parts of a field the shape of the land keeps wet.
  3. 3.Catchment — All the land that drains to one culvert, draw or low corner.
  4. 4.Landforms — Hollows, valleys and footslopes at a glance: where water gathers.

How to use it

  1. Select a property, draw an area or upload a boundary.
  2. Run. Switch between the stream network and ponding views in the panel.
  3. Export the channels as GeoJSON or KML to open in GIS or Google Earth.

Step by step: Mount Hood

We follow where rain and snowmelt run off Mount Hood’s south side, and where it would pond.

1.Zoom to the area or select a property, then choose Preview on map.

2.The stream network: the panel gives the total length and number of channels. Thin, dark lines are small draws high up; thick, bright lines are where they meet and carry the most water.

3.Switch to Ponding. The panel gives the area, the greatest depth and the volume. Long blue strips along a road usually mean a culvert the terrain does not know about.

What it showed

  • Check where the main channels run before placing a building, a driveway or a septic system.
  • Culverts and pipes are not in the terrain, so water backed up behind a road fill is a place to check, not a prediction.
Try it yourself on Mount Hood →

How it works

Small pits in the USGS 3DEP bare-earth model are filled so water can always find a way downhill. Each cell then passes its water to its steepest neighbor, and the number of upstream cells is counted for every cell. Cells that collect more than a threshold are drawn as channels and ranked by Strahler order, where two first-order streams meeting make a second-order stream.

Ponding compares the filled surface with the original ground: wherever the fill raised the ground, water would stand there, and the difference is the depth.

Reading the results

Thicker, higher-order lines carry more of the area’s water. First-order lines are the small feeder draws.

Ponding depth, area and volume describe the low spot when full. Real ponds drain into the soil and evaporate, so these are upper bounds.

Limits and caveats

  • Culverts, pipes, levees and ditches narrower than the sampling are not in the terrain, so water is routed over roads and through embankments.
  • Channels are cut off at the edge of the area. Use Catchment to see where a channel’s water comes from beyond the boundary.
  • Where lidar has not been flown, the USGS 3DEP model falls back to its 1/3 arc-second layer, about 33 ft per pixel, and downloads state what share of the area came from it. That coarser model is not fit for site-scale decisions. DOGAMI reports about 99% of Oregon covered by at least one lidar project. The fallback is rare.

Data and attribution

Results come from the USGS 3D Elevation Program (3DEP) bare-earth elevation model: lidar at 3.3 ft per pixel where it has been flown, and the 1/3 arc-second model, about 33 ft per pixel, elsewhere, with elevations above NAVD 88. The tools with a surface option (Sunlight, Viewshed, Sightline, Object Heights) read DOGAMI’s statewide digital surface model of trees and buildings.

USGS 3DEP elevation data and USGS maps are U.S. Government works in the public domain: you may use the results, including commercially. A credit to the USGS 3D Elevation Program is appreciated, and every file you download carries it. DOGAMI lidar products are published by the State of Oregon; credit "DOGAMI / Oregon Lidar Consortium". County taxlot boundaries are the assessor's GIS data, not surveys, and each county publishes its own disclaimer, shown with the parcel. The aerial basemap is from Esri and follows Esri's terms; it is not included in downloads.

Questions

Is this a flood map?

No. It shows where terrain sends water and where it can sit, not flood depths for a given storm. For flood hazard, check FEMA’s flood maps and your county.

What does it miss?

Culverts, pipes, levees and ditches narrower than the sampling are not in the terrain, so water is routed over roads and through embankments. Check the result against what you see on site.

Ready to try it?

Open Water & Drainage on the map →

Free to use, no account. The analysis runs in your browser on public-domain USGS 3DEP data. Downloading the results needs a pass: see pricing.