Tutorial 04 Rivers and faults

Part of the tutorial: page 4 of 12

▶ Watch this page: part 4 of the tutorial video (about 2 min), with narration and subtitles.

Tutorial 4: Rivers and faults

Add and remove river sources, draw a river of your own, and open a rift valley with a tectonic feature, reshaping it by its points and with Undo.

Start from: 03-climate-and-biomes.json, the map as it is at the end of Tutorial 03 Climate and biomes. Download it, then open Maps on the rail and click Import JSON; the map is listed under its name, and Load opens it. Or carry on with your own map from Tutorial 03 Climate and biomes.

Rivers are worked out by themselves: they rise where the land is high and wet enough, and run downhill to the sea or into another river, pooling into lakes in hollows on the way. The Rivers and faults tool lets you move where they rise, draw rivers of your own, and draw tectonic features that reshape the land around a line.

Steps

1. Click Rivers and faults on the rail, the last tool in the Shape group, then choose Source on the bar. Every river source the module placed is shown as a ring: a river rises at each one.

   

   Source mode: a ring marks every river source.

2. The dry east of the continent has no rivers. Zoom in on it, and click the high ground in the middle of the desert, south-east of the inland sea's eastern bay: a river source is added there, and its river runs west across the desert to join the river flowing into the bay.

   

   The new river crossing the desert.

   A river source you add makes a river whatever the land and climate are like there. Drag a source to move it.

3. The north-west is crowded with rivers. Click Reset view and zoom in there, then Ctrl+Click (Cmd+Click on macOS) the middle ring of the three in a row south of the two snow-capped peaks. Its river is gone, and a black marker shows where it was removed; Ctrl+Click the marker to bring it back.

   

   A removed river source, marked in black.

4. The southern forests have no rivers. Choose River on the bar and set River width to Medium. Then click from the hills in the south of the continent eastwards to the coast, and right-click to finish. A custom river runs exactly along your line, from its higher end to its lower, and the ground is lowered into a gentle valley around it.

   

   The custom river across the southern forests.

   The new river opens in the inspector as you place its first point; Reset view in the map controls shows the whole map beside it. If your line ends on land, the river carries on downhill from its end by itself.

5. Now a tectonic feature. Choose Fault on the bar, set Tectonic fault type to Rift, Fault line thickness to 90 and Fault line strength to 0.15, for a shallow rift that floods only in places. Click across the south of the continent from the west coast to the east coast, starting and ending a little out to sea, and right-click to finish. A rift is land being pulled apart: a valley of tilted blocks with raised shoulders, its floor flooding where it drops below sea level. Drawing it on past both coasts lets it open into the sea, since a rift rises back to the ground level at its ends.

   

   The rift across the south of the continent, open to the sea at both ends.

   Tip: draw a tectonic feature where the land or seabed suits it: a rift across a continent, a mountain range along high ground, a subduction zone along a coast facing the ocean, a hotspot chain across open sea. See Rivers and faults for each feature's settings, which open in the inspector.

6. Every line you draw keeps its points, so you can reshape it afterwards. Drag the rift's middle point a little south: the rift is worked out again along its new line.

   

   The rift with its middle point dragged south.

   While drawing, Shift+Click the line to add a point and Ctrl+Click a point to delete it.

7. Click Undo (top right of the map, or press Ctrl+Z). The point goes back where it was, and the rift with it. Every change you make is one step of undo, and Redo beside it puts the change back.

   

   After Undo: the rift is back on its first line.

8. Choose Select on the bar to stop drawing, close the inspector, click Reset view, and save the map. That completes the land: the next tools populate it.

What you should see

A new river across the desert in the east, one river fewer in the north-west, a river of your own across the southern forests to the east coast, and a rift valley across the south of the continent, open to the sea at both ends.

To compare your map with the tutorial's, or to start the next page from exactly this map, download 04-rivers-and-faults.json and import it in Maps with Import JSON.

In Foundry

Everything on this page is the same in Foundry.

On your own map

Check the rivers once the terrain and climate are settled: a terrain edit can change their course. The Hydrology section sets how high and how wet the land must be for a river to rise, and how wide and winding rivers are. Tectonic features take on the character of the ground they cross, so look at it first: a Mountain range along hills, a Subduction zone along a coast facing the ocean, a Rift across a continent, a Hotspot chain across open sea. On a large map, Pause regeneration on the bar lets you place several points before the terrain is worked out again.

Next: Tutorial 05 Populating the world

Related: Rivers and faults, Terrain, FAQ