Bushwalking Navigation | Using Creek Lines in Arid Environments

Ever wondered why it is so easy to get lost following a creek in an arid environment? What precautions can you take? Why is it more difficult to navigate uphill than downhill?

I have just come back from 4 days in the Vulkathunha-Gammon Ranges, over 700 km north of Adelaide where rainfall averages less than 20 mm per month with most of it falling during summer as the tail end of monsoons in the north west of Australia sweep down into northern South Australia and temperatures rise into the mid to high 30s. This has been one of the best start to the bushwalking season for many years and there are large numbers of full waterholes in the creek beds, lots of weed infestations and even a mouse plague.

Walking is usually via dry rocky creeks beds, as the ridges are often steep, rugged and exposed. Sometimes the creeks are full of native vegetation such as paperbarks (Melaleuca) and flood debris which makes movement with a full pack difficult.

Invariably navigation is a challenge, as few, if any, of the creeks have flowing water to help decide which way is downstream and it is difficult to distinguish major tributaries from mere gully's. Often creek beds are hundreds of metres wide and may have islands in the middle, which can give the impression of a creek intersection, leading to miscounting.

Creek navigation involves

• starting from a known location (use your GPS)
• deciding how far away the next creek intersection will be and whether it will be on the left or right
• calculating your walking speed and using elapsed time as a guide to when the next intersection should occur
• counting creek intersections as you go
• checking map to ground as you walk for obvious features such a gorges, cliffs, bends in the creek and stopping if they don't appear in the correct sequence and place
• using your compass to check the direction of each creek at each intersection with that expected from the map
• checking for debris against tree trunks and trickling creeks to decide which way the creek is flowing
• checking your location frequently with your GPS, even if you think you know where you are, as often parallel creek beds, can appear to be very similar. 
• deciding on a catching feature so you don't go too far or a handrail you can follow (see below for glossary)

If you have a GPS, then set up a route linking waypoints you have pre-determined at each creek intersection (decision point). This will give you distance to the next intersection, time to next intersection and bearing, but has severe limitations if the creek bed is very windy as all directions are "as the crow flies". The GPS should never be relied upon without confirmation from map to ground, especially in narrow gorges where reception can be poor.

Uphill navigation following creek lines is always more difficult than downhill, as there always at least two uphill choices at each intersection but coming downhill, it is unlikely that you would decide to go back uphill at the intersection, knowing that the main creek must be going downhill.

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