SGUK Outdoor Skills Challenge 40: Predict Where Water Will Pool After Rain

After a spell of heavy rain, some parts of the ground dry quickly while others remain muddy for days. You can often predict where the water will collect before the rain even starts, simply by looking at the shape of the land, the soil and the way the surrounding ground drains.

This is a useful skill for anyone who spends time outdoors. It can help you choose a better place to pitch a tent, avoid muddy paths and understand why certain parts of a campsite become waterlogged. The trick is to look beyond the surface and work out where water is likely to travel when gravity takes over.

Your Challenge

Choose a safe outdoor area and study the ground to identify at least five places where rainwater is likely to collect or flow. Before the next rainfall, record your predictions and explain what features of the landscape led you to them.

After it rains, return to the area if conditions are safe and compare your predictions with what actually happened.

What You’ll Need

• A notebook and pencil or a phone for recording your predictions.
• Suitable outdoor clothing and footwear.
• A simple sketch or photograph of the area, if useful.
• Access to the same area before and after rainfall.

Take the Challenge

1. Look at the shape of the ground

Start by looking at the landscape as a whole. Water flows downhill, so depressions, hollows and the bottom of slopes are good places to look for possible pooling.

A shallow dip in a field might not be obvious when the ground is dry, but look across it from a low angle and you may notice the change in level. On a woodland path, a slight hollow between raised edges can act like a channel, collecting water that runs off the surrounding ground.

Identify three low points and write down whether you think water will collect there. Don’t just look at the lowest spot immediately around you; consider where water could travel from further uphill.

2. Examine the soil and surface

The ground itself affects how much rainwater soaks in and how much runs across the surface. Sandy or gravelly soil often allows water to drain away more readily than compacted clay, although the result depends on the soil beneath it and how wet it already is.

Look for compacted ground on paths, frequently used grass areas and places where people or vehicles regularly pass. These surfaces may absorb less water, allowing rain to run towards nearby hollows.

Clay-heavy ground can remain wet for a long time, particularly after prolonged rain. Bare soil may also become muddy where water flows over it. Make a note of the ground type where you can identify it, but avoid assuming that appearance alone tells you exactly how quickly water will drain.

3. Find natural channels and slopes

Follow the shape of the land with your eyes. A slope directs water towards lower ground, while small channels can concentrate runoff into a narrow route.

Look for shallow grooves, worn tracks, dips between raised areas and places where vegetation appears to follow a line downhill. These may indicate where water has travelled during previous rainfall.

Pay attention to what lies at the bottom of each route. Water may spread out across a flat area, collect in a hollow or continue towards a ditch or stream. Your task is to predict where it will go next, rather than simply marking the first low point you find.

Never enter a drainage channel or approach a fast-flowing stream to investigate it. Observe from a safe position.

4. Check the ground around obstacles

Fences, walls, tree roots, raised path edges and other obstacles can influence how water moves. A wall may direct runoff along its base, while a raised path can prevent water from draining naturally across the ground.

Look for places where the flow might be diverted or trapped. A small hollow on the uphill side of an obstacle could collect water, while a gap may allow it to pass through.

Trees can make the situation more complicated. Their roots and surrounding soil may influence runoff, while the canopy can intercept some rainfall before it reaches the ground. Don’t assume that every spot beneath a tree will stay dry; water can run down trunks, drip from branches and flow across the surrounding soil.

5. Make five predictions

Choose five locations in your area and record what you expect to happen after rain. For each location, write down:

• Where you think the water will collect or flow.
• What features of the land led you to that conclusion.
• Whether you expect a temporary puddle or ground that stays wet for longer.

For example, you might predict that water will collect in a shallow dip on a path, run along the bottom of a grassy slope, or gather on compacted ground beside a raised edge.

Be specific enough that you can check your prediction later. Instead of writing “the field will be wet”, identify the particular hollow or section of ground you expect to hold water.

6. Check your predictions after rain

Once it has rained, return to your observation area when it is safe to do so. Avoid flooded paths, unstable banks, fast-flowing water and areas where poor visibility or slippery ground creates a hazard.

Compare the actual conditions with your notes. Did water collect where you expected? Did it drain away more quickly than you thought? Did a channel carry water towards a different low point?

Rainfall intensity and duration matter. A brief shower may not produce much runoff, while prolonged or heavy rain can saturate the soil and overwhelm normal drainage routes. Your predictions may therefore be accurate after one downpour but differ after a light shower.

Record what you learned and consider whether the ground type, slope or drainage features explain the result.

7. Apply what you’ve learned to campsite selection

The same observations can help you choose a more suitable place to camp. Avoid hollows, obvious drainage routes, the bottom of slopes and ground that is already waterlogged. A spot that looks flat and comfortable during dry weather may become unpleasant or unsafe when rain arrives.

Choose firm, well-drained ground and follow the site’s rules and any local guidance. Don’t pitch in dry streambeds, flood channels or places where water may rise quickly. Even if a location appears dry, it may be part of a route used by runoff during heavy rain.

Check Your Results

Review your five predictions and compare them with the conditions after rainfall.

• Did you identify low points where water collected?
• Did you recognise areas where compacted or less permeable ground encouraged runoff?
• Could you follow the likely direction of water downhill?
• Did obstacles or drainage channels change the route?
• Did you account for the amount of rain and how wet the ground was beforehand?

You don’t need to predict every puddle correctly. What matters is being able to explain your reasoning and improve it after seeing what happened.

Complete the Challenge

To complete Challenge 40, you must:

1. Study a suitable outdoor area before rainfall.
2. Identify at least five places where water may collect or flow.
3. Record why you chose each location.
4. Compare your predictions with the conditions after rain.
5. Take a photograph of your observation area or notes as evidence.

If rainfall doesn’t arrive while you’re working on the challenge, you can still record your predictions and submit them, then add your observations after the next suitable rainfall.

How to Submit Your Challenge

Share your evidence

1. Go to your SGUK member profile.
2. Open Social Activity.
3. Upload a photograph of your notes, sketch or observation area.
4. Add the hashtag #SGUKChallenge40.
5. Share it for verification.

You can include one prediction that proved correct and one that surprised you. Your observations may also help other members learn how to read the landscape.

Once you’ve shared your evidence and it has been verified, the SGUK Outdoor Skills Challenge 40 is complete and the completed challenges figure will be updated on your profile.

Challenge 40 Checklist

Want to Push Yourself?

Try the same exercise in two different places, such as a woodland path and an open grassy area. Compare how the slope, vegetation and soil affect the movement of water.

You could also sketch a simple map using arrows to show the direction you expect runoff to travel. Mark the low points, possible channels and places where water might escape. After rain, update the sketch to show what actually happened.

What’s Next?

Understanding where water collects is useful when planning a route or choosing a campsite. If you haven’t completed it yet, try SGUK Outdoor Skills Challenge 39: Learn the Risks of Carbon Monoxide When Cooking in a Tent to build your awareness of another important aspect of camping safety.

You can complete SGUK Outdoor Skills Challenges in any order, so choose whichever skill you’d like to practise next.

Learn. Practise. Master.

That’s what the SGUK Outdoor Skills Challenge is all about.