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Hydrologic Response Units

Units of common soils, land cover, and slope used in continuous simulation modeling.

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: Hydrologic Soil Group Number (0 = A/B, 1 = C, 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 commands below can be used to access this layer within the Google Earth Engine Code Editor. A Google Earth Engine account is required.

// 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"]

Viewing

Individual objects contain all the info used in the stormwater heatmap. To add it to the map, add the layer object.

var display_image = layer_name.layer
Map.addLayer(display_image)

Analysis

To get the raw image data for analysis, access the eeObject key.

var raw_image = layer_name.layer.eeObject
Map.addLayer(raw_image,{},'Hydrologic Response Units')

Visualization

Palette

LabelRaster valueColors
Outwash, Forest, Flat0#e5f5f9#e5f5f9
Outwash, Forest, Moderate1#99d8c9#99d8c9
Outwash, Forest, Steep2#2ca25f#2ca25f
Outwash, Pasture, Flat10#e0ecf4#e0ecf4
Outwash, Pasture, Moderate11#9ebcda#9ebcda
Outwash, Pasture, Steep12#8856a7#8856a7
Outwash, Lawn , Flat20#e0f3db#e0f3db
Outwash, Lawn , Moderate21#a8ddb5#a8ddb5
Outwash, Lawn , Steep22#43a2ca#43a2ca
Till, Forest, Flat100#ece7f2#ece7f2
Till, Forest, Moderate101#a6bddb#a6bddb
Till, Forest, Steep102#2b8cbe#2b8cbe
Till, Pasture, Flat110#ece2f0#ece2f0
Till, Pasture, Moderate111#a6bddb#a6bddb
Till, Pasture, Steep112#1c9099#1c9099
Till, Lawn , Flat120#e7e1ef#e7e1ef
Till, Lawn , Moderate121#c994c7#c994c7
Till, Lawn , Steep122#dd1c77#dd1c77
Saturated, Forest, Flat200#fde0dd#fde0dd
Saturated, Forest, Moderate201#fa9fb5#fa9fb5
Saturated, Forest, Steep202#c51b8a#c51b8a
Saturated, Pasture, Flat210#edf8b1#edf8b1
Saturated, Pasture, Moderate211#7fcdbb#7fcdbb
Saturated, Pasture, Steep212#2c7fb8#2c7fb8
Saturated, Lawn , Flat220#f7fcb9#f7fcb9
Saturated, Lawn , Moderate221#addd8e#addd8e
Saturated, Lawn , Steep222#31a354#31a354
Impervious, Flat250#fee6ce#fee6ce
Impervious, Moderate251#fdae6b#fdae6b
Impervious, Steep252#e6550d#e6550d

Source

The Nature Conservancy