Dealing with the rise in the sea level and higher river discharges

In Europe it is either drought or flood

The consequences of climate change will be different for different parts of Europe: in one place it will be drier on average and in another place it will be wetter on average. In addition, in the same area different extremes could interchange with each other: longer dry periods and longer wet periods. In the future Europe will more frequently have too much or too little water.

The rise in sea level due to climate changes requires coastal defences

Sea level rise due to climate change calls for coastal defence. Since 1990 the future sea level rise has been taken into account in the management of our coast. This has happened in three ways:

  • through using the anticipated rise;
  • through assuming a rise in sea level of 60 cm/century when making investments that have a planned lifespan of 50-100 years;
  • through assuming the upper level of the KNMI predictions of 85 cm/century for precautionary measures for the coming 200 years.

Every year 12 million cubic metres of sand from the North Sea are brought to the coastal area. This supplementation provides sufficient protection against the current sea level rise of approximately 20 cm/century. If more of the coastal foundation threatens to disappear under water over the course of time, then the volume of sand will be increased. If the sea was to rise by 85 cm in the coming hundred years, then annually 60 million cubic metres of sand would be added. Thanks to this supplementation, we are managing to maintain the coastline with its beaches and dunes at the required level and no beaches will disappear due to the rising sea level. Elsewhere in the world, for example with small sandy beaches along rocky coasts, it could be a different story.
For the construction and maintenance of works with a lifespan of approximately 50-100 years, such as dikes, a rise in the sea level of 60 cm per century will be assumed. The strength of these dams will be tested every five years using the latest scientific insight into the strength that the sea water can exert against the dams.

The rising sea level will make beaches disappear

Sea level rise due to climate change calls for coastal defence. Since 1990 the future sea level rise has been taken into account in the management of our coast. This has happened in three ways:

  • through using the anticipated rise;
  • through assuming a rise in sea level of 60 cm/century when making investments that have a planned lifespan of 50-100 years;
  • through assuming the upper level of the KNMI predictions of 85 cm/century for precautionary measures for the coming 200 years.

Every year 12 million cubic metres of sand from the North Sea are brought to the coastal area. This supplementation provides sufficient protection against the current sea level rise of approximately 20 cm/century. If more of the coastal foundation threatens to disappear under water over the course of time, then the volume of sand will be increased. If the sea was to rise by 85 cm in the coming hundred years, then annually 60 million cubic metres of sand would be added. Thanks to this supplementation, we are managing to maintain the coastline with its beaches and dunes at the required level and no beaches will disappear due to the rising sea level. Elsewhere in the world, for example with small sandy beaches along rocky coasts, it could be a different story.
For the construction and maintenance of works with a lifespan of approximately 50-100 years, such as dikes, a rise in the sea level of 60 cm per century will be assumed. The strength of these dams will be tested every five years using the latest scientific insight into the strength that the sea water can exert against the dams.

The climate has not always caused it

During the summer of 2007 a number of rivers burst their banks in England after it had been raining for a long period. According to the media the flooding in England was due to climate change.
An extremely wet month need not have anything to do with climate change. The weather is so fickle that such extremes are possible without climate change. Only after a long period, in which many such extremes have taken place, can it be statistically established whether an extreme summer such as that in England in 2007 is part of the trend of a changing climate.
Large quantities of persistent rain in the same area do not happen very often. There can be many years between two similar extremes in the same area, years in which the land use can change drastically. In countries such as England and the Netherlands there has been a lot of building in flood-sensitive areas in the last century. If it now rains heavily, it can cause far more damage and inconvenience than before. It appears then that climate change is leading to large-scale flooding while in fact the scale of the flooding itself has not changed but the resulting damage has increased because we are now living closer to the water. Thus the climate is not always been the cause.

Title

Lorem ipsum ...

Controlled flooding reduces the flooding elsewhere

The Dutch river dikes can safely keep out an extremely high water level. If we want to protect ourselves against even higher water levels (with an even smaller chance of occurring) then that higher river level can be managed through the raising of dikes and the construction of new rivers.

New rivers increase the discharge capacity between the dikes. That new rivers are advocated against flooding from climate change is therefore understandable: it is a measure that reduces the probability of flooding. Up until 2015 more space for water will be provided between the dikes of the Rhine and the Meuse in the Netherlands. Not by constructing new rivers, but by digging more washland, removing obstacles in the winter bed, digging side gullies by the main gully, extending local dikes and by raising dikes where river widening is not feasible.
The probability of a flood can also be reduced by allowing a flood to occur elsewhere (an emergency overflow) where a flood can cause relatively little damage. A controlled flood restricts the flooding elsewhere. However this is not a straightforward option. The social resistance against the designation of emergency flood plains is so great that areas previously selected have been deselected.

The dikes are not high enough to cope with the rise in sea level

 As soon as a dam no longer reaches this standard, it will be reinforced taking into account a rising sea level of 60 cm per century. Thus the dikes will always be high enough to cope with the rising sea level.
The Dutch coast must be reinforced in order to be able to cope with the rise in sea level and greater wave strength. When being reinforced, the sea walls will be made higher as well as wider.  Space has already been reserved behind the dams for possible future reinforcements, starting with the expected maximum scenario of 85 cm rise in sea level per year over a term of 200 years.

The Dutch coast must be reinforced in order to deal with the rise in the sea level and greater wave strength

 As soon as a dam no longer reaches this standard, it will be reinforced taking into account a rising sea level of 60 cm per century. Thus the dikes will always be high enough to cope with the rising sea level.
The Dutch coast must be reinforced in order to be able to cope with the rise in sea level and greater wave strength. When being reinforced, the sea walls will be made higher as well as wider.  Space has already been reserved behind the dams for possible future reinforcements, starting with the expected maximum scenario of 85 cm rise in sea level per year over a term of 200 years.

Coastal areas are at increasing risk through the rise in the sea level

If coastal areas do not arm themselves against the rising sea, they are running increasing risks because of the rising of the sea level. The KNMI considers the probability to be small that the sea level at the Dutch coast will rise by more than 85 cm by 2100 in comparison with 1990. However, even if it were to rise this century by one to one and a half meters, then the increase can be controlled by extra sand supplementation to the coast, adaptations to the sea dikes and innovations such as wave-resistant dikes.

A rise in the sea level of 2 to 3 meters over the coming centuries can be dealt with easily by sand supplementation and higher dikes. In this timescale river widening and dikes are still the solution to the rise in sea level and higher river discharge. In any case we will then have to look at the areas where the problem of higher river discharge and a rising sea level are combined. These are the lower reaches of the Rhine and Meuse (in particular the areas around Rotterdam-Dordrecht) and Lake Ijssel (where higher Ijssel discharge can be less easily drained into Lake Wadden (Waddenzee).

The coast can easily cope with the predicted rise in the sea level of one to one and a half meters in the coming century

If coastal areas do not arm themselves against the rising sea, they are running increasing risks because of the rising of the sea level. The KNMI considers the probability to be small that the sea level at the Dutch coast will rise by more than 85 cm by 2100 in comparison with 1990. However, even if it were to rise this century by one to one and a half meters, then the increase can be controlled by extra sand supplementation to the coast, adaptations to the sea dikes and innovations such as wave-resistant dikes.

A rise in the sea level of 2 to 3 meters over the coming centuries can be dealt with easily by sand supplementation and higher dikes. In this timescale river widening and dikes are still the solution to the rise in sea level and higher river discharge. In any case we will then have to look at the areas where the problem of higher river discharge and a rising sea level are combined. These are the lower reaches of the Rhine and Meuse (in particular the areas around Rotterdam-Dordrecht) and Lake Ijssel (where higher Ijssel discharge can be less easily drained into Lake Wadden (Waddenzee).

Dikes are the solution to the rise in the sea level

If coastal areas do not arm themselves against the rising sea, they are running increasing risks because of the rising of the sea level. The KNMI considers the probability to be small that the sea level at the Dutch coast will rise by more than 85 cm by 2100 in comparison with 1990. However, even if it were to rise this century by one to one and a half meters, then the increase can be controlled by extra sand supplementation to the coast, adaptations to the sea dikes and innovations such as wave-resistant dikes.

A rise in the sea level of 2 to 3 meters over the coming centuries can be dealt with easily by sand supplementation and higher dikes. In this timescale river widening and dikes are still the solution to the rise in sea level and higher river discharge. In any case we will then have to look at the areas where the problem of higher river discharge and a rising sea level are combined. These are the lower reaches of the Rhine and Meuse (in particular the areas around Rotterdam-Dordrecht) and Lake Ijssel (where higher Ijssel discharge can be less easily drained into Lake Wadden (Waddenzee).

The floods in England were caused by climae change

During the summer of 2007 a number of rivers burst their banks in England after it had been raining for a long period. According to the media the flooding in England was due to climate change.
An extremely wet month need not have anything to do with climate change. The weather is so fickle that such extremes are possible without climate change. Only after a long period, in which many such extremes have taken place, can it be statistically established whether an extreme summer such as that in England in 2007 is part of the trend of a changing climate.
Large quantities of persistent rain in the same area do not happen very often. There can be many years between two similar extremes in the same area, years in which the land use can change drastically. In countries such as England and the Netherlands there has been a lot of building in flood-sensitive areas in the last century. If it now rains heavily, it can cause far more damage and inconvenience than before. It appears then that climate change is leading to large-scale flooding while in fact the scale of the flooding itself has not changed but the resulting damage has increased because we are now living closer to the water. Thus the climate is not always been the cause.

Meltwater from the glaciers forms a small part of the total water flow

The larger rivers that flow through the Netherlands are the Rhine and the Meuse. The Meuse is a rain river and the Rhine is both a rain and a meltwater river. The meltwater from the Rhine comes from the glaciers and snowfall in the Alps. Meltwater from the glaciers forms a small part of the total water flow because the surface of glaciers, including the volume of ice in the Alps, is very small in relation to the surface of the catchment area of the Rhine. If all the glaciers in the Rhine catchment area were to melt in the next 50 years, the discharge at Lobith would increase by less than 1% as a consequence. The melting of glaciers will therefore neither cause flooding nor a shortage of water.

However the consequences of climate change for the snowfall in the Alps and with that the discharge from the Rhine is much greater. The area of the Alps where snow falls each winter is after all much larger than the area which is covered with ice. In the current climate this snow stays on the ground until the following spring. Therefore in the winter, when normally speaking the highest discharge occurs at Lobith, there is little water in the Rhine from the Alps. In the late spring and summer the melting snow increases the discharge at Lobith and thus the meltwater contributes to a smaller probability of low water in this period.

In the short term the melting of glaciers will cause floods; in the long term it will cause a water shortage

The larger rivers that flow through the Netherlands are the Rhine and the Meuse. The Meuse is a rain river and the Rhine is both a rain and a meltwater river. The meltwater from the Rhine comes from the glaciers and snowfall in the Alps. Meltwater from the glaciers forms a small part of the total water flow because the surface of glaciers, including the volume of ice in the Alps, is very small in relation to the surface of the catchment area of the Rhine. If all the glaciers in the Rhine catchment area were to melt in the next 50 years, the discharge at Lobith would increase by less than 1% as a consequence. The melting of glaciers will therefore neither cause flooding nor a shortage of water.

However the consequences of climate change for the snowfall in the Alps and with that the discharge from the Rhine is much greater. The area of the Alps where snow falls each winter is after all much larger than the area which is covered with ice. In the current climate this snow stays on the ground until the following spring. Therefore in the winter, when normally speaking the highest discharge occurs at Lobith, there is little water in the Rhine from the Alps. In the late spring and summer the melting snow increases the discharge at Lobith and thus the meltwater contributes to a smaller probability of low water in this period.

The consequence of the earth’s warming for the Netherlands is that the rivers will swell due to melting snow peaks

Climate change means that the precipitation in the Alps in the winter will be more often in the form of rain and less in the form of snow. This means that the winter discharge from the Alpine area will be greater and the discharge in the spring and summer will be smaller. In the period in which the highest discharge now appears at Lobith, the Rhine discharge will be still higher. The Rhine will, just as the Meuse, be a river that is primarily fed by rainfall. The Rhine will not swell because of melting snow peaks but because of more rain. In the summer period low discharge will occur more often and sooner because there is no more meltwater available.

Deforestation in poor countries causes an increase in flooding

The Dutch river dikes are designed to protect the country from extremely high river discharge. The extremely high discharge appears only when it rains long and hard on a big scale, in the catchment area of the rivers and when the substratum is saturated or frozen. In these circumstances it makes little difference what the land use in the area is: the ‘sponge’ of the substratum is saturated and the precipitation quickly ends up in the rivers.
Poor countries in, for example, Asia have a much lower level of protection than the Netherlands. Relatively frequent high waters can lead to problems and then the type of land use is of importance. The more frequently occurring high waters appear in quantities of precipitation that in themselves are not so extreme for these areas. With this precipitation the substratum of a wooded area is not yet saturated and the ‘sponge’ can still absorb a lot of water. The ‘sponge effect’ dampens the extent of the river discharge. However if the region’s wooded areas are turning into agriculture or urban areas, the sponge effect is reduced. Rain then flows more quickly towards the river and the amount of discharge can become high. Thus deforestation in poor countries causes an increase in the number of floods.

Higher river levels can be solved by raising dikes and constructing new rivers

 The Dutch river dikes can safely keep out an extremely high water level. If we want to protect ourselves against even higher water levels (with an even smaller chance of occurring) then that higher river level can be managed through the raising of dikes and the construction of new rivers.

New rivers increase the discharge capacity between the dikes. That new rivers are advocated against flooding from climate change is therefore understandable: it is a measure that reduces the probability of flooding. Up until 2015 more space for water will be provided between the dikes of the Rhine and the Meuse in the Netherlands. Not by constructing new rivers, but by digging more washland, removing obstacles in the winter bed, digging side gullies by the main gully, extending local dikes and by raising dikes where river widening is not feasible.
The probability of a flood can also be reduced by allowing a flood to occur elsewhere (an emergency overflow) where a flood can cause relatively little damage. A controlled flood restricts the flooding elsewhere. However this is not a straightforward option. The social resistance against the designation of emergency flood plains is so great that areas previously selected have been deselected.

New rivers are advocated to cope with flooding caused by warming

The Dutch river dikes can safely keep out an extremely high water level. If we want to protect ourselves against even higher water levels (with an even smaller chance of occurring) then that higher river level can be managed through the raising of dikes and the construction of new rivers.

New rivers increase the discharge capacity between the dikes. That new rivers are advocated against flooding from climate change is therefore understandable: it is a measure that reduces the probability of flooding. Up until 2015 more space for water will be provided between the dikes of the Rhine and the Meuse in the Netherlands. Not by constructing new rivers, but by digging more washland, removing obstacles in the winter bed, digging side gullies by the main gully, extending local dikes and by raising dikes where river widening is not feasible.
The probability of a flood can also be reduced by allowing a flood to occur elsewhere (an emergency overflow) where a flood can cause relatively little damage. A controlled flood restricts the flooding elsewhere. However this is not a straightforward option. The social resistance against the designation of emergency flood plains is so great that areas previously selected have been deselected.