Understanding topographic features for your hikes

Navigating the great outdoors can sometimes feel daunting, especially when it comes to reading a topographic map. However, understanding how to interpret these maps is essential for any hiker. They provide valuable information about the landscape, showing not only the basic landmarks but also the intricate details of the terrain.

What Are Topographic Maps?

Topographic maps are two-dimensional representations of a three-dimensional landscape. Their primary function is to illustrate the shape of the land, including how it rises and falls. This information is vital for determining the best approach to a mountain or valley. Unfortunately, many hikers I encounter on the trail seem unsure of their location or direction. Some may not carry a map at all, while others struggle to read it.

Learning to read a topographic map isn’t as challenging as it may seem. With some training, practice, and ongoing use, anyone can master it. The symbols, contour lines, and directional indicators on the map can be deciphered with a little patience.

Decoding Contour Lines

Contour lines are crucial elements of topographic maps. They represent elevation changes in the landscape:

• Close Contour Lines: Indicate steep terrain. The closer the lines are, the steeper the slope.
• Far Apart Contour Lines: Suggest flatter terrain. The greater the distance between the lines, the gentler the slope.

Contour Intervals

The contour interval represents the vertical height difference between adjacent contour lines. Most topographic maps use a contour interval of 10 metres, but this can vary based on the terrain:

• 20 Metres: Common in steep areas.
• 5 Metres: Often used in flat regions.

You may also encounter form lines (broken brown lines), typically found on orienteering maps, which indicate height for features less than 10 metres high.

Key Land Forms to Recognise

Understanding specific land forms can significantly enhance your navigation skills. Here are a few important features:

• Hills and Knolls: Represented by loop contours or several concentric loops, indicating the height of the hill.
• Saddles: Low points between two knolls, appearing like a saddle, with higher ground on two sides and lower ground on the other two sides.
• Steep and Flat Terrain: Look for contour lines that are close together for steep areas and spaced apart for flat ground.
• Gullies and Spurs: A gully is a small valley where water flows during wet weather, while a spur is a ridge jutting out from a hill. In Australian terrain, erosion often creates a pattern of gullies and spurs. To distinguish between them, note that spurs point away from the highest point (the knoll), while gullies point towards it.

Navigating Up and Down

Determining which way is uphill or downhill can be tricky. Here are a few tips to help you navigate:

• Index Contours: Look for the thicker contour lines, usually marked every 100 metres, which show specific heights.
• Identify Watercourses: Water flows downhill, and its courses will be lower than the surrounding land. As you move downstream, watercourses typically merge and grow larger.
• Closed Loop Contours: These indicate hilltops, with the surrounding land dropping off in elevation.

Experienced orienteers often navigate by carefully analysing contour lines and matching them with the physical landscape. This skill is especially valuable in many parts of Australia, where distinct gully-spur landforms dominate the scenery.

Learning on the Trail

The best way to master map reading is through practice in the field. Combining theoretical knowledge with hands-on experience will reinforce your understanding of the landscape features. So grab your map, head out, and start exploring—your confidence will grow as you learn to interpret the contours of the land around you.

Some Important Land Forms

Hills and Knolls – Hills and knolls (or small hills) are shown by a loop contour or several concentric loop contours depending on how high the hill is.

Saddles – Named after a horse rider’s saddle, it is a low point between two knolls. It looks up to higher ground on two sides, and looks down on to lower ground on the other two sides.

Steep and Flat Terrain – Contour lines close together indicate steep terrain; contour lines a long way apart indicate flatter terrain.

Gullies and Spurs – A gully is a small valley, usually where water runs in wet weather. A spur is a sloping ridge jutting out from the side of a hill. In most Australian terrain, hillsides have been eroded to form a series of gullies separated by spurs. Every bend in a contour indicates either a gully or spur. It is crucial to be able to tell which of the two it is. To distinguish between a gully and a spur. Find the highest point (the knoll) SPURS point away from the knoll and downhill GULLIES point towards the knoll and uphill. On many topographic maps gullies can be picked by the blue lines denoting watercourses.

How to know which way is uphill and downhill? It is not always easy to tell! Topographic maps have a thicker ‘index’ contour, usually every 100 m, that have heights marked that you can match up to work out up and down. Alternatively, locate a high point or a low point, and follow the contours from there. Here’s a few hints:

1. Watercourses flow in land lower than that immediately surrounding them.
2. Water flows downhill. Watercourses get larger and join each other as they flow down to lower country.
3. Look for closed loop contours indicating hill tops. The land immediately surrounding is lower

Experienced orienteers do much of their navigation by carefully reading the contours, and matching them with the shape of the landscape around them. This is particularly so in many parts of Australia where there is a distinct ‘gully-spur’ landform covered in open forest, with very little other detail. Interpreting features of the landscape is best learned in the terrain with a map. It can also be reinforced by undertaking suitable theoretical exercises.