in Design
Rivers in justified text
Rivers are channels of white space that run down through justified text. Why they form, how to spot them, and how to get rid of them.
A river is a line of white space that seems to flow down through a block of text, formed when word spaces in successive lines happen to fall close to one another. Once you have seen one, it is hard to stop seeing it. The eye follows the white channel instead of the words.
Rivers are almost always a feature of justified text, and they are one of the most common signs that a page has been set in a hurry.
Why they form
Justified text is aligned on both the left and right edges. To achieve that, the typesetting software has to adjust the space in each line so that it fills the measure exactly. Most of that adjustment happens in the word spaces.
When the word spaces in a line are stretched well beyond their natural width, gaps open up. If gaps in consecutive lines line up vertically, or nearly, they read as a single channel. Rivers can meander diagonally as well as running straight down, and the loose word spacing that causes them is often visible even when no clear river has formed.
Several conditions make rivers more likely: a narrow measure, which gives each line fewer spaces to share the adjustment; a large type size for the measure; long words, which are hard to fit; disabled or restricted hyphenation; and loose word-spacing settings that allow very wide spaces.
How to spot them
Rivers are easier to see when you stop reading. Turn the proof upside down, hold it at arm’s length, or look at it with your eyes half closed. The text becomes a grey texture, and any channels of white stand out against it.
On screen, zooming out has the same effect, although print proofs remain more reliable.
How to get rid of them
Improve the composition. Good layout software can consider a whole paragraph at once when deciding where to break lines, rather than making each line work on its own. In Adobe InDesign this is the Adobe Paragraph Composer; the approach traces back to the line-breaking algorithm Donald Knuth and Michael Plass developed for TeX. Paragraph-level composition spreads spacing more evenly and produces fewer rivers.
Tighten the spacing limits. Justification settings define how far word spaces may shrink or stretch. Narrowing that range forces the software to find better breaks. Some designers also allow a very small amount of letter spacing or glyph scaling, but these should be kept to amounts that no reader could see.
Allow sensible hyphenation. Hyphenation gives justified text far more places to break, and it is usually the single most effective remedy. It needs its own careful settings, so that the cure is not worse than the disease.
Reconsider the measure or the size. If rivers keep appearing, the column may simply be too narrow for the type. A slightly smaller size or a slightly wider measure can solve many problems at once.
Fix individual paragraphs. After the global settings are right, a few paragraphs will still misbehave. A typesetter can adjust tracking very slightly on a single paragraph, or, with the agreement of the author or editor, change a word.
Or do not justify
Ragged-right setting, where lines end naturally and the right edge is uneven, keeps word spaces consistent and cannot form rivers in the same way. It suits narrow columns and some kinds of book very well. Most novels are still justified, by convention and because a well-justified page looks settled, but that is a choice rather than a requirement.
Either way, the aim is even texture: a page whose colour is steady enough that nothing in it pulls the eye away from the words.