Cases of Coastal Erosion
Coastal erosion is a natural process that can be accelerated by improper land use. It has become a large problem in the Gulf of Mexico, especially in Louisiana and Texas for several reasons. In Texas and (1) ___________there is a process known as alongshore drift. This means that the ocean currents move a specific direction and so sand and other sediment is moved alongshore (along the shore) in (2)_______________. When rivers are dammed they no longer supply sand to the river deltas and this alongshore drift cannot resupply the beaches with sand. The beaches eventually (3) _____________ and begin to erode. On the eastern coast of the United State alongshore drift is northward, so barrier islands and other beaches tend to migrate northward. On the west coast of the US the drift is southward and so beaches lose sand where anything blocks the southward movement. Some jetties have been built that began to starve the beaches southward of sand supply and this has become a problem for those beaches.
In Louisiana the problem is a little different because there are several factors (4) _______________ of coastal erosion. Louisiana is losing 18,500 acres of wetlands each year to coastal erosion. One large part of the problem is that this area was once part of the Mississippi River delta floodplain, and as levees have been built to prevent flooding, the areas have been deprived of additional sediment supply from the river. Another part of the problem is that the sediments that the area is built on tend to settle over time. The Mississippi River has built a pile of sediments of sand and mud (5) _____________. With time this sediment compacts and sinks, causing flooding where the surface is no longer being resupplied from the river. Even another factor has been discovered that this part of the North American continent is sinking possibly as a response to the melting of glaciers on the upper part of the continent about (6) ____________. Since the northern part of the continent is still rising because of the weight of the ice removed when the glaciers melted, it works like a teeter-totter and the southern part is going down. This coastal erosion was in large part the cause of much of the damage to New Orleans during last yearís hurricanes, as it created storm surge conditions that were more extreme than expected.
Figure 8.2 Iceland Coastal Erosion
8.2.3. Read the text again. Decide which statements refer to Texas (T) and which to Louisiana (L):
1. The sand is moving in particular directions.
2. The beaches lose sand with the lapse of time.
3. The shores erode very quickly.
4. Natural disasters caused erosion.
5. The river canít supply the sand to the beaches because of the dams.
6. There are three factors that cause coastal erosion.
8.2.4.Read the following text and use the word given in bold at the end of each line to form a word that fits in the space on the same line:
Date: 2015-12-11; view: 604