Human interaction with Rivers LC

How humans interact and effect river processes:

Three ways humans can influence the natural processes a river carries out are by

1)    Shortening  the Rivers course

2)    Construction of dams

3)    Building of artificial levees/dykes/embankments

 

1)    Shortening of the Rivers course:

·        As the river Rhine is such an important artery of trade it was decided to shorten its course by approx. 100km.It is an important waterway as it connects the North Sea, Mediterranean Sea and the Black Sea. 

·        Meanders have now been bypassed and new channels created and as a result the Rhine is now shorter, straighter and deeper.

·        The impact of this is that it has doubled the speed of the waters flow from Basle to Rotterdam. Thus its rate of erosion has increased and caused water to cascade down when there is heavy snow or rain upstream.

 

2)    Construction of dams:

·        Since the 1950’s HEP stations have been built along the upper section of the River Rhine and this has increased the problem of flooding. Thirteen HEP stations were built along the French-German border under the ‘Power Project’ and this involved the construction of a new section of the river parallel to the old Rhine. Countries are investing heavily as HEP is a renewable energy source and as fossil fuel continue to be depleted.

·        These dams cause sediments to be trapped and this reduces the rivers load. As a result the water after the dam is rejuvenated and is flowing faster which in turn transfers water downstream at a quicker pace.

·        In China the Three Gorges dam was built along the River Yangtze. This dam is 185 km high and 1.6km wide. It is used to generate power to some of the major cities such as Shanghai and to prevent flooding.

·        However as a result it has stopped the transportation of fertile alluvium downstream and now farmers have had to buy expensive fertilisers instead.

·        Also the natural habitat has been affected and as a result in 2007 the Yangtze dolphin was declared extinct.

·        In Ireland the Ardnacrusha (HEP) Scheme on the Shannon and the Blessington Lake- reservoir Co. Wicklow have been built and these have impacted numerous fish such as the salmon.

 

3)    Artificial levees/embankment/Dykes

·        Previously when the Rhine flooded it spread across the floodplains however now over 85% of its natural floodplains have been lost due to agriculture and buildings and so embankments needed to be built in order to protect these.

·        However this has closed off the natural floodplains and has simply moved the flooding downstream this previously wouldn’t have been at risk of flooding.

·        This has also resulted in more sediments being deposited in the river bed. As this has raised the level of the river then the embankments also need to be raised which in turn continues to cost the countries effected money to do so.

·        As the size of ships using the river increased in size stretches of the river were narrowed to create a deeper channel and so the river began to flow faster and the rate of erosion increased.

·        If floods pushed to towards the mouth then Dutch polders at serious risk of submergence.

·        The River Rhine flooding is now almost an annual event and in January 1995 Cologne ended up 2 metres underwater due to this, Also in the Netherlands 250,000 people and animals/poultry had to be evacuated and this seriously affected both sides of the Ijssel which is a highly intensive horticulture and agricultural area.