Colour legend
The colour bars explain the map display. They are not a flood-risk certificate, and they are not a substitute for the exact point readout, local modelling, field knowledge, or official warnings.
HAND - height above nearest drainage
What it means
HAND is the height of the land above the nearest mapped drainage line. Low values usually sit in valley bottoms, near rivers, streams, lakes, or drainage routes. Higher values usually sit on slopes, shoulders, and ridges.
The default HAND layer uses the 0.025 square kilometre stream-initiation threshold chosen for this build.
How to read it
Yellow is low relative ground. Orange and brown are intermediate ground. Purple is higher relative ground.
Transparent areas are undefined HAND cells. That can happen around ridges, landlocked depressions, or places below the stream threshold.
Slope - steepness of the ground
What it means
Slope is the steepness of the terrain in degrees, calculated from the breached DEM. It helps explain how quickly water may move over the land surface.
Flat or gentle ground tends to hold, spread, or slow water. Steeper ground can move water faster downhill.
How to read it
Dark colours are flatter ground. Bright orange/yellow is steep ground. The display scale is capped at 45 degrees plus so extreme slopes do not flatten the rest of the map.
The point readout can still show exact sampled slope values.
TWI - topographic wetness index
What it means
TWI estimates where terrain shape encourages wetness. It combines upslope contributing area with local slope using ln(a/tan beta).
Broadly: more contributing area and gentler slope can mean greater wetness tendency.
How to read it
Dark purple/blue is lower relative wetness tendency. Green/yellow is higher relative wetness tendency.
The colour display is clipped around the common upper range. Exact TWI can be higher than the visible `6.3+` end of the bar.