Introduction

“Investigate why the characteristics of the River Glaven lead to the need for flood management”

Hypothesis:

1. As you go downstream the width and depth will increase, this means that the capacity of the river will increase, therefore making it less likely to flood.

2. As you go downstream discharge1 will increase, therefore the amount of water carried in the channel is higher and so could potentially increase flood risk.

The River Glaven is located in UK, East England, in North Norfolk (map 1). The source of the river is Bodham and the river flows 16.3km where it reaches the mouth at Cley-next-to-the-Sea which empties into the North Sea (map 2). The highest point above sea level is only 75m. It has a small catchment area of only 115km² and therefore the river is quite small in general.

Map 1 – Map to show the location of Norfolk in the UK

Map 2 – Map of North Norfolk outlining the location of the River Glaven.1 Discharge – how much water is in the river.

Norfolk where the River Glaven is located

Background theory

I am examining whether width, depth and discharge all increase as the river flows downstream. This theory is clearly noted via the Bradshaw model (diagram 1). If they all increase the potential for flooding is increased for discharge as there is more water in the river. For the width and depth the likelihood of flooding will decrease as the river now has a larger capacity.

Diagram 1 – The Bradshaw Model

All decrease downstream

All increase downstream

Background information

The river has already had flood management. The river has had a major restoration project that took place in August 2010. The project took place over 400m of the river and had already prior to this restoration had some changes made i.e. straightening the river which probably happened for milling purposes. The restoration in August was restoring some of the features such as back pools, riffles and meanders as well as narrowing it and connecting it back up to its flood plain. It was done to make the river flood in this piece of the river instead of downstream to the local mill. Since the refurbishments it has been seen that the riffles are now full of invertebrates and aquatic plants. The restoration seems to have been a success.

There is also a minimum chance of flood as the geology of the area is chalk based (which means it is porous). Surrounding ground is dry so can soak up water. Taking all facts into consideration means there are no significant flooding issues. The flooding issues that do occur can be managed with changes on a small scale and monitoring at gauging stations. There are five mills that interrupt the river but only one mill (Letheringsett) is still fully operational and is the only one in Norfolk too.