Rivers - Crossings

1. Many different river crossings have been developed over time.

2. Stepping stones are one of the oldest river crossings.

3. Stepping stones were a prehistoric invention and are the only type of bridge not to involve a span.

4. As long as there was enough space between the stones for the water to flow through, they were quite successful.

5. A ford is a shallow place in a river or stream that allows it to be crossed by wading, or driving on horseback or in a car.

6. Fords usually happen naturally.

7. Fords become impassable after heavy rain as the road will be submerged when the river level is high.

8. Bridges are the most common river crossings

9. They were built over rivers and canals to allow people or vehicles to cross them.

10. Timber was used to build the first bridges, but, later stone and concrete were used as stronger bridges were needed.

11. The earliest bridges were made by placing logs or planks over the top of stepping stones.

12. The design of any bridge depended on its function and the nature of land it was being built on.

13. Many bridges in the past were made from short, arched spans.

14. Any number of spans could be combined together to make a long bridge.

15. The spans had to be short to stop the bridge from collapsing.

16. However, too many piers going into the water could slow the flow of the river and cause problems.

17. Suspension bridges are often built over rivers where they are at their widest.

18. Strong brick or stone columns are built into the river banks, or into the river itself.

19. Massive steel cables are slung between the tops of the columns.

20. The cables curve downwards in the middle because of their weight.

21. Smaller steel cables hang from them holding the road or rail deck below.

22. Movable bridges are often needed over rivers, canals or at the entrances to harbours.

23. Some bridges, like Tower Bridge in London, can be raised to allow tall ships to pass through.

24. Swing bridges pivot around a gear mechanism.

25. In its closed position, a swing bridge carrying a road over a river or canal allows traffic to cross.

26. When a boat needs to pass the bridge, road traffic is halted and the motors rotate the bridge.

27. Some bridges, like Robert Stephenson’s High Level Bridge over the River Tyne, are designed for both vehicles and trains.

28. The bridge was the first of its kind in the world, with rail traffic on the upper deck and road traffic on the lower.

29. Sometimes, tunnels are used to cross beneath a river such as in the Dartford River Crossing.

30. An aqueduct is an artificial channel for water built to carry water from one place to another.

31. Aqueducts often look like bridges and carry water over a valley or hollow.

32. Large, navigable aqueducts carry canals over other rivers, railways, valleys or roads and can be used by boats or ships.