Allgäu forest plays an important role as a brake when there is too much water.
Was that why the Allgäu was lucky in disaster during the most recent storms in July?
Was even greater damage prevented in the settlement areas because the forest, the mountain forest, has largely fulfilled its functions?
Such questions were and are being discussed more and more, both in water management and in forest administration and protection forest management.
One thing is clear: the forest can also be an “umbrella”, a brake when there is too much water.
In any case, it plays an important role.
“The function of the mountain forest can best be seen where it no longer exists.
Look at the countries in southern Europe where forests were cut down in earlier times.
The erosion can no longer be stopped even by the most complex technical measures, and in the event of flooding the mud and water masses shoot unchecked into the valleys, ”says Karl Schindele, head of the Kempten water management office, depicting a scenario that one would rather not experience.
Mountain forest holds back water
“This is why the mountain forest is incredibly important for erosion protection and natural water retention in the area.
In the event of major floods, however, the mountain forest alone cannot adequately protect our settlements.
The technical flood protection must also be implemented here. "
In Bavaria there are three specialist units for protective forest management.
They are based at the offices for food, agriculture and forestry in Kempten, Weilheim and Rosenheim.
The protection forest management is a repair company.
The Bergwaldoffensive is about prevention.
Can the mountain forest guarantee flood protection?
When water overflows, it is very quickly not just a matter of belongings, but of life and limb.
The events of the recent past have brought issues of flood prevention (again) into focus.
Flood protection is one of the most important protective forest functions.
Can the mountain forest actually make a contribution?
If yes, which one?
Karl Schindele: “It can, but not indefinitely.
When it comes to avoiding or reducing floods in the Allgäu, the forest in the mountains is at the beginning of the causal chain. "
Deep roots, lots of storage space
When it comes to retaining water, the most important thing happens underground, explains Schindele.
“Of all land use forms, the mixed mountain forest has the lowest surface runoff.
That doesn't mean that forest floor can soak up unlimited water. ”If it rains hard enough and or long enough, the“ sponge forest floor ”will eventually be too full to hold the water.
It only stores it where there are pores.
No pores without roots.
The more intensely and deeply a soil is rooted, the higher its storage capacity.
The deep-rooted fir tree is particularly valuable here.
But: It depends on the mix of tree species.
"The fir needs good company."
The large amount of water required by trees has a positive effect.
They cover it by drawing water out of the ground.
The nature of the soil also plays a role.
Forests can even improve "bad" soils.
Grass with a root depth in the centimeter range cannot keep up.
Bare rock does not store water
And people also play an important role.
Silvicultural measures have a positive or negative effect.
Gaps in the tree population should be as small as possible, and maximum caution is required when harvesting wood.
Area-wide driving should be avoided because the water absorption capacity decreases when the soil is compacted.
The positive effects can also be seen above ground.
Trees hold back water in their crowns and it evaporates through needles and leaves.
Retained and evaporated water does not get into the soil.
This reduces the amount of water to be stored and relieves the soil.
And clearly.
Trees (branches, twigs, needles, leaves) break the kinetic energy, which is particularly important in the event of heavy precipitation, because it dampens the impact on the ground.
So soil is erosion protection.
Closed mountain forests prevent soil erosion by almost 100 percent.
Wherever ground has disappeared in the mountains, it never comes back.
Technical measures are laborious, expensive and not always successful.
Bare rock does not store water.
