Holland is essentially a delta area, bringing three major European rivers to the sea: the Rhine, Maas (the Meuse) and Schelde are the major components of the so characteristic Dutch river landscape. You may notice several landscape aspects:
You see high dikes at some distance from the water. Between the dike and the water you see meadows, farmhouses laying on small hills, and more and more natural areas with willow trees, reed, creeks etcetera. This typical area between the dyke and water is called "uiterwaard" in Dutch. It means something like outside land.
About dykes and floods
In summer the water levels in the rivers are low. You may notice the low summer dikes, preventing the uiterwaard to flood if it rains more than usual. The ground can be used as meadows in this time. In winter, water level is much higher. This would require very high dikes. The Dutch found a better solution. They use the uiterwaard as spare capacity for the river. The high winter dyke protects the land. In 1993 we had extremely high water levels. In some areas of the country it became a really dangerous situation. In that time over 100.000 people were evacuated. Since that time the Dutch government decided improvements for the dikes were necessary. Not only by making dykes higher, but also by reserving more space for the water. In some areas flooding of houses is quite common, it happens once in a few years.
Usually a flood is not caused because the water streams over the dike, but because the bottom side of the dike starts leaking water. It looses its stability and may break then.
In the picture above you see a sketch showing how the system works in summer.
In winter you see the summer dyke may disappear under water. The winter dike gives protection. I exaggerate quite a lot in this picture, normally the water will stay just at the foot of the dyke.
An important use of the uiterwaard are the stone bakeries or stone factories as we say. Holland does not have mountains, so natural stones are very rare. The rivers bring large amounts of clay down from the mountains. Because clay consists of small particles, they only will drop if the water is streaming quite slow. The uiterwaarden are a very good place for clay deposits. This resulted in the Dutch stone bakeries you will see at many places along the rivers. This also explains why you see so many houses constructed of bricks in Holland. The stone factories dig the clay in the uiterwaarden. The holes form small lakes.
Wild cows and horses
Uiterwaarden are more and more used as nature reservates.To keep the grass short and to prevent trees to grow, nature protection organisations use half wild cows (usually Galloways) and horses. If you hike in these areas, you should be aware of this. It is better not to touch them and keep a safe distance of at least 25 metres.