Hydrologic Response Units
Units of common soils, land cover, and slope used in continuous simulation modeling.
| Earth Engine asset | Hydrologic_Response_Units (open) |
| Period | released 2026-11-02 |
| Units | HRU |
| Data type | Categorical |
| Pixel size | 2.4 m (EPSG:3857) |
| Pixel type | uint8 |
| Download | Cloud-Optimized GeoTIFF (666.4 MB) |
| Catalog entry | STAC item |
Description
Hydrologic response units (HRUs) are discretized landscape units based on common soils, land cover, and slope characteristics. The HRU approach provides a computationally efficient method of pre-computing hydrologic response for later use. Results for a particular watershed can be calculated by summing or averaging the results for individual HRUs.
Each combination of parameters was modeled in separate batched simulations. HRUs were designated by a three-digit number according to the following convention:
- First digit: Soil type (0 = Outwash, HSG A/B; 1 = Till, HSG C/D; 2 = Saturated)
- Second digit: Land cover (0=Forest, 1=Pasture, 2=Lawn, 5=Impervious)
- Third Digit: Slope (0=Flat, 1=Mod, 2=Steep)
For example, a site with Type C soils, with forested land cover, on a
moderate slope would be represented by 101. This schema allowed for
HRUs to be stored as an eight-bit unsigned integer on a Puget-Sound wide
raster, minimizing storage size.
Layer Access in Earth Engine
The JavaScript below loads this layer in the Earth Engine Code Editor. An Earth Engine account is required. The "open" links above show each asset's details in the Code Editor.
// Import the layer data dictionary
var data = require('users/stormwaterheatmap/apps:data/public')
// To view data dictionary, print to the console:
print('Data:', data)
// Get this layer from the layer data dictionary:
var layer_name = data.rasters["Hydrologic Response Units"]
// Add the styled layer to the map:
Map.addLayer(layer_name.layer)
// Raw image for analysis:
var raw_image = layer_name.layer.eeObject
Map.addLayer(raw_image, {}, 'Hydrologic Response Units')
Visualization
| Label | Raster value | Color |
|---|---|---|
| Outwash, Forest, Flat | 0 | #E5F5F9 |
| Outwash, Forest, Moderate | 1 | #99D8C9 |
| Outwash, Forest, Steep | 2 | #2CA25F |
| Outwash, Pasture, Flat | 10 | #E0ECF4 |
| Outwash, Pasture, Moderate | 11 | #9EBCDA |
| Outwash, Pasture, Steep | 12 | #8856A7 |
| Outwash, Lawn , Flat | 20 | #E0F3DB |
| Outwash, Lawn , Moderate | 21 | #A8DDB5 |
| Outwash, Lawn , Steep | 22 | #43A2CA |
| Till, Forest, Flat | 100 | #ECE7F2 |
| Till, Forest, Moderate | 101 | #A6BDDB |
| Till, Forest, Steep | 102 | #2B8CBE |
| Till, Pasture, Flat | 110 | #ECE2F0 |
| Till, Pasture, Moderate | 111 | #A6BDDB |
| Till, Pasture, Steep | 112 | #1C9099 |
| Till, Lawn , Flat | 120 | #E7E1EF |
| Till, Lawn , Moderate | 121 | #C994C7 |
| Till, Lawn , Steep | 122 | #DD1C77 |
| Saturated, Forest, Flat | 200 | #FDE0DD |
| Saturated, Forest, Moderate | 201 | #FA9FB5 |
| Saturated, Forest, Steep | 202 | #C51B8A |
| Saturated, Pasture, Flat | 210 | #EDF8B1 |
| Saturated, Pasture, Moderate | 211 | #7FCDBB |
| Saturated, Pasture, Steep | 212 | #2C7FB8 |
| Saturated, Lawn , Flat | 220 | #F7FCB9 |
| Saturated, Lawn , Moderate | 221 | #ADDD8E |
| Saturated, Lawn , Steep | 222 | #31A354 |
| Impervious, Flat | 250 | #FEE6CE |
| Impervious, Moderate | 251 | #FDAE6B |
| Impervious, Steep | 252 | #E6550D |