Why contours are your first safety tool

Before you leave the car, the map already tells you whether your planned route is a gentle amble or a leg-burning grind. Contour lines are the key. They turn a flat sheet of paper into a three-dimensional landscape, showing every rise, every hollow and every steepening of the ground. Learning to read them fluently is the single most useful hillwalking skill you can develop — more useful, in many ways, than a compass bearing, because contours tell you what the ground is actually doing before you commit to it.

On British hill maps, contours are usually drawn at 10-metre vertical intervals. That means every line represents a height above sea level, and the gap between lines shows how quickly you gain or lose that height. The closer the lines, the steeper the slope. The wider the gap, the gentler the going. It really is that simple — but the detail is where the skill lies.

Spacing: the language of steepness

Start by looking at the spacing. If contour lines are far apart, you are looking at easy, rolling ground — the kind of terrain where you can chat and eat a sandwich. If they bunch together, the slope is steepening. If they almost touch, you are looking at a steep drop, a crag, or ground that will demand hands on rock. On a 1:25,000 map, contours that merge into a solid black band usually mean a cliff face. Avoid those unless you are deliberately scrambling and know what you are doing.

Even spacing means a uniform slope — no surprises. Uneven spacing, where lines alternate between close and wide, tells you the slope is broken by terraces or small shelves. That can be useful: those shelves often make natural rest stops or safe places to reassess. But they can also hide unexpected drops. Always ask yourself: if I walk up this line, what will the ground feel like under my boots?

Shapes: spurs, valleys and ridges

Contours are not just about steepness. Their shapes reveal the bones of the land. A V shape pointing uphill (towards higher ground) marks a valley, a beck or a re-entrant — a hollow in the hillside. Water collects there, and the ground is often boggy. A V shape pointing downhill marks a spur or ridge — a finger of higher ground sticking out into lower ground. Spurs are your friends: they offer drier, firmer walking and often a clear line of ascent.

Where two summits are linked by a dip, you will see a saddle or col — two sets of concentric rings with a lower gap between them. That is a natural crossing point. Where contours form a series of tight, concentric rings, you have a summit or a knoll. The innermost ring is the highest point. If the rings are very close together, the summit is sharp and the final pull will be steep.

Ridges are shown by long, narrow bands of contours that run in a line, with ground falling away on both sides. Following a ridge is often the safest way up a hill in poor visibility, because you have a handrail of descending ground on either side. But be careful: some ridges have unexpected steepenings or rocky steps. Check the spacing as you go.

Spotting crags and steep ground

Crags are marked not just by tight contours but often by short black hachures — little tick marks that point down the slope. These are a clear warning. If you see hachures on a section of your route, the ground is broken by rock. It might be a small outcrop you can step around, or it might be a serious cliff. Without local knowledge, assume the worst and plan a detour.

Also watch for contours that suddenly stop or bunch into a thick line where a stream or a road cuts through. That can indicate a steep-sided gorge or a waterfall. In winter, these places hold snow and ice long after the rest of the hill has thawed. In summer, they can be slippery and loose. A route that looks fine at a glance can become a serious undertaking if you ignore these details.

One practical trick: trace your planned line of ascent with your finger. Every time the contour spacing tightens, ask yourself how many contours you are crossing and how much height that represents. Ten contours at 10 metres each is 100 metres of ascent — a decent pull. Twenty contours is a serious climb. If they are packed into a short horizontal distance, you are in for a steep, tiring slog.

Planning a route with contours in mind

Let us say you want to reach a summit from a valley car park. The direct line might look shortest, but if the contours are tightly packed all the way up, it will be exhausting and possibly dangerous. Instead, look for a spur or ridge that takes a longer, gentler line. The contours will be more widely spaced, and you will have natural handrails. You might add a kilometre to your walk but save yourself an hour of struggle and a lot of risk.

Use contours to plan escape routes too. If the weather turns, where can you drop off the hill safely? A broad spur with gentle contours is a good option. A steep, hachured crag is not. Note these options before you set off, and mark them mentally. Also count the total ascent: add up the contour crossings on your planned route. A typical hill day might involve 800 to 1,000 metres of ascent. If your route has 30 contour crossings on the way up alone, you know it will be a big day.

Finally, remember that contours are only half the story. They do not show vegetation, bog, or path quality. But they show the shape of the land — and that is the foundation of every safe hill route. Read them carefully, and you will walk with more confidence, less effort and far fewer nasty surprises.