Bella Bear's Global Adventures from Sussex in the UK to the Amazon Rainforest and Madagascar
WATER AND FLOODING
The Lewes Railway Land Nature Reserve is situated on the edge of the River Ouse on a flat piece of land known as a flood plain. As the name suggests this is the natural area of a river that floods when water level is very high.
Even though the land is now a nature reserve it is still allowed and even encouraged to flood when necessary. During times of exceptional flooding parts of the nature reserve are covered in water.
In the past, many towns, including Lewes, were built next to rivers because they provided an important source of water. Rivers were also a great way of transporting goods and people around the country at a time when there were few roads and before railway. Some towns grew up in places where the river was spanned by a bridge or where a ferry took peoe across the river.
The right hand photograph shows the flood water level from the river Ouse in October 2000 when there was a particualry big flood. It is marked on the Linklater Pavillion wall, but the flood occurred before the Pavillion was built.
Much of this flooding is due to the Winterbourne Stream which flows through the north end of the nature reserve and is an important part of the patchwork of interconnecting habitats. As its name suggests it only really flows in the winter.
In the summer the winterbourne is a slow meandering stream.
Winterbourne Stream
Play the video above which shows how dramatic the flooding can be. Filmed 13th January 2016
In the UK we no longer need to live near water, but houses close to rivers are still popular places for people to live becaue of the beautiful views and soothing nature of life near a river.
Unfortunately many houses have been built on flood plains which is not a good thing. Our warming climate due to man made climate change is causing the sea level to rise which effects rivers too and more moisture in the air means more rain and a greater chance that flood plains will flood, including any houses that are built on them.
Many miles of land around a river are drained by a river system of streams. Water from the high ground runs eventually into the river. This area of land is called the watershed.
Lewes Railway Land Nature Reserve and Seasonal Flooding
In the winter months, a much larger volume of water flows along the winterbourne and direct into the River Ouse.
However at high tide, there is a large flap at the point at which the winterbourne stream enters the river and so as the tidal water rises the weight of water closes the flap.
This means that the Winterbourne cannot escape to the river and so it backs up getting deeper and deeper until it tips over into the woodland and into heart of reeds. The Winterbourne stream water level may rise by two and a half metres.
Summer view (above). Winter view (below)
Some of this water at the north end of Heart of Reeds (reed bed) goes through a pipe to the pond dipping area and then by another pipe to chilly brook meadows.The water that floods into the woodland will eventually reach the Leighside pond which is then temporarily engulfed.
By allowing the Winterbourne to naturally flood the reserve, this saves about 8 cellars in Lewes town from being flooded on every high tide. As the tide level in the River Ouse falls, the Winterbourne stream can again flow back into the river Ouse.
When it rains, the rain water from the surrounding hills will run into streams like the Winterbourne and all these streams will eventually flow into the river. This is added to by water from towns that flow into the river through the storm drains.
During winter storms this can be a lot of extra water flowing into the river. If it is high tide, when the river is naturally deeper, there is a big danger that this water will flood. This is why the Winterbourne is allowe dto flood into the reed bed.
Streams and Watershed.
Climate Change
Our climate is changing due to a global rise in air temperature caused by carbon dioxide from the burning of fossil fuels. This rise in temperature is contributing to sea level rise and flooding. This has also caused the oceans to become warmer to. This 'global' warming is causing more Polar ice to melt and causing oceans to expand causing a rise in sea level. This sea level rise not only threatens coastal aras but rivers too as many are very tidal.
Warmer oceans release more moisture into the air and so this means more storms too, especially winter storms which can also cause flooding.
But of course some places will have less rain and may suffer from drought. It is possible that we may have wetter winters and hotter dries summers. We will need to adapt to these changes and so will animals and plants.
TO FIND OUT MORE ABOUT THE OCEAN CLICK THE FOLLOWING LINK TO VISIT ED THE BEAR WEBSITE. CLICK VISIT ED THE BEAR
TO FIND OUT MORE ABOUT HOW SEA LEVEL RISE MIGHT AFFECT THE RIVER OUSE AND LEWES VISIT THE RAILWAY LAND LIVE WEBSITE. CLICK CLIMATE CHANGE