Question

Give and example and explanation of how dams cause erosion

Answer 1

Step-by-step explanation:

Downstream Erosion occurs when a dam is constructed, disrupting the natural downstream flow of sediment. Take the Hoover Dam on the Colorado River as an example, where sediment that would typically replenish downstream ecosystems is trapped. Consequently, the river downstream of the dam experiences increased clarity and speed, leading to heightened erosion of riverbanks and the riverbed. This erosion is exacerbated because the sediment, which would normally replenish these areas, is now withheld.

Step-by-step explanation:

Sediment Starvation:

The dam confines sediment that would usually be deposited downstream, resulting in erosion as the river attempts to compensate for the absence of new material.

Altered Flow Regimes:

Controlled water releases from the dam often lack the natural variability crucial for shaping riverbanks and floodplains. This uniform flow can contribute to increased erosion.

Increased Water Velocity:

The reduced sediment content in the water allows it to flow more rapidly, enhancing its erosive power on both riverbanks and the riverbed.

Answer 2

Dams, such as hydroelectric power structures, can cause significant environmental damage including erosion of turbines and alterations to river ecology, with the Vajont Dam in Italy being a notable example of geological instability and erosion due to inadequate planning and environmental consideration.

Step-by-step explanation:

Dams cause erosion in several ways, and an example of this can be seen in the environment surrounding hydroelectric power dams. When rivers are dammed up, large areas of forest may be flooded, not only eliminating additional forest habitat but also increasing the water's acidity due to the decomposing plant material. This acidic water can lead to erosion of the hydroelectric turbines, thus shortening their lifespan and creating long-term maintenance issues. Sediment build-up behind dams can displace water, reducing the capacity of reservoirs and leading to environmental degradation.

Moreover, dam reservoirs cause changes in water temperatures, flow characteristics, and silt loads which disturb the natural river habitats both upstream and downstream of the dam. These changes can significantly alter the river's ecology and physical characteristics, wreaking havoc on the species that depend on that habitat. One stark example is the Vajont Dam in Italy, where inadequate geological surveys and a narrow valley selection led to a catastrophic landslide, underscoring the potential for erosion and geological instability caused by dam construction and reservoir filling.