Environmental Impact
The building of a large structure such as a bridge will have effect the environment in many ways, including the aural, environmental, material, and visual impacts.
Aural means hearing. This often overlooked effect can have disastrous results for the local wildlife and/or residents around the bridge. A quiet park full of bird, squirrels and deer can become an abandoned grass field in a few short years if living things are scared away by the roaring noise of a new freeway overhead.
People that have lived in a quiet area may suddenly find their peaceful neighborhood changing very quickly as a result of a bridge.
The construction of a bridge can be a very damaging process to the
local area when it is being built. Even if trees are replanted and
grass sown, the area will often never be the same again. How a
bridge is constructed in such environmentally-sensitive areas is just as
important as what it looks like.
Bridges that cross over water must not alter the water flow or the natural users of the river. An example are fish that migrate along a river; a bridge that blocks their passage would have huge environmental impacts along the entire river since other wildlife might go hungry if the fish are not able to reproduce.
The materials that are used in bridge construction have to come from somewhere,
and if they are from non-renewable sources (cannot be replaced within 100
years) then there will be a negative impact on the environment. Wood
is an example of a renewable resource.
The finished bridge should not seem completely out of place in its
surroundings either. This is related to the principles of aesthetics,
but goes beyond how the bridge looks itself. A massive concrete
bridge would be completely inappropriate for a park bridge over a stream,
while a small arch bridge painted in wood-like colors would blend in with
the area.
See also construction site.