Using rivers, lakes and coastlines for navigation

Water bodies follow a clear order: water flows downhill, small streams join to form larger ones, these form rivers, and lakes and coastlines have shapes that do not change as quickly as a forest track. This order makes water reliable features. Flow direction points downhill, a confluence is an unambiguous point, and a lake shore or a coastline is a long line you can hardly miss.

On the map, water tells you a lot about the terrain. Where a stream crosses contour lines, they usually form a 'V' or 'U' whose point faces upstream. This lets you see which way is up and which is down even without height figures. A stream always lies in a hollow or a valley, never on a ridge – which helps you match valleys and ridges on the map correctly.

In navigation you use water in two ways. As a handrail, you walk on a path beside the water and tick off tributaries, bridges and islands. As a catching feature, a stream or lake shore lies across your route: when you reach it, you know you have gone far enough – or too far.

A common piece of advice says that if you are lost you should follow a stream downhill because it will lead you to people. This is dangerous. Stream courses often get narrower and steeper, lead into gorges, over drops and waterfalls, or into marshes and dense, impassable bankside vegetation. First clarify your position (stop, calm down, check the map), then choose a safe route – that may be a path running along the stream at a safe distance, but not the stream bed itself.

Using water as a handrail does not mean crossing it. River crossings are dangerous: current, cold and slippery stones are easily underestimated, and even knee-deep fast water can knock a person over. When in doubt, look for another route or a bridge. After heavy rain or during snowmelt a stream can swell quickly, even if it is not raining where you are. Also avoid balancing across wet stones along the bank.

On tidal coasts the water rises and falls about twice a day in many places, and the times shift from day to day. Beaches, rocky points, shoreline paths and tidal flats can be flooded in a short time, cutting off the way back. Check the tide table for that exact place beforehand, plan your return with a generous buffer and heed local warning signs. In an emergency, call the local emergency number (112 in the EU).

Study the water on the map beforehand: which way does it flow? Where do tributaries join, and on which side? Where are bridges, footbridges, islands, bays or distinctive shoreline shapes? These are your checkpoints. The more of them you know in advance, the more confidently you can confirm your position on the way.

Small streams are tricky. Some only carry water part of the year and dry up in summer; some maps draw such streams as dashed lines. Conversely, after rain, trickles appear that are on no map. Confuse such streams and you can quickly end up in the wrong valley. Large, permanent water bodies are therefore more reliable as handrails than small ones.

Bankside paths are often harder going than expected: wet, slippery, overgrown, with many side streams. Allow more time and rather stay on a path at a safe distance from the bank than struggle along right next to the water.

Water features are ideal for valley walks, on lake and coastal paths and as a catching feature on compass legs. They are especially strong as catching features: a wide river across your route stops you from walking far past your target without noticing.

They are less suitable in trackless gorges and on steep stream courses, on tidal coasts and tidal flats without a current tide table, and in floods, when banks and paths may be under water. Water bodies also change: drought, floods and construction can alter banks, stream courses and paths, while the map stays the same.

Land navigation manuals list water bodies as typical handrails and catching features. At the same time, mountaineering literature and rescue organisations warn against river crossings and against descending along stream courses without thought. Both belong together: water is an excellent signpost, but not a path.

And one more point that has nothing to do with navigation but is often asked: even clear stream water can contain pathogens. If you have to drink it, disinfect it first, for example by boiling, and follow the advice in the water entries.