Impact of People on the Coastline Humans have

Impact of People on the Coastline Humans have tried to modify the coast to make it more stable – more suitable for building homes, hotels, etc.

Impact of People on the Coastline Humans try to prevent coastal erosion mainly in one of 2 ways: A. By interfering w/ the longshore drift or transport of sand & B. By redirecting wave energy striking a stretch of beach

Methods of Stabilization A. Breakwaters B. Groins C. Jetties D. Seawalls E. Beach replenishment

Breakwaters 1)Breakwaters are generally built offshore & parallel to the beach. These long structures protect the beach from wave action. Breakwater

Breakwaters 2)The negative consequence of a breakwater is that when the waves are blocked natural sand movement is also blocked, causing coastal erosion downshore.

Breakwaters 3)

Breakwaters

Breakwaters

Groins 4)Groins are rock structures built perpendicular to the shore. Groins are built on eroding beaches to trap sand & promote accretion. Groins

Groins 5)The negative consequence of groins is that groins cause erosion on the downshore side of the groin. Groins

Groins 6) Groins

Groins

Groins

Groins

Jetties 7)Jetties are built to keep river, lagoon & other waterway channels open. They stabilize the openings for marinas, ports & harbors. Jetties

Jetties 8)Like groins, jetties are made of large boulders or concrete materials & are built perpendicular to the shore. Jetties

Jetties 9)The negative consequence of jetties is that they cause erosion on the downshore side. Jetties

Jetties 10) Jetties

Jetties

Jetties

Seawalls 11)Seawalls are built on the shore to prevent erosion of the beach especially by storms. 12)However, the problem is seawalls increase the turbulence of the water at the front of the barrier, which promotes erosion at the bases of the

Seawalls 12)Ultimately, the seawall is weakened, undermined & destroyed by the pounding of the waves.

13)

Seawalls

Before After Seawalls

Is there an alternative?

Alternatives to Artificial Barriers 14)Beach replenishment is the process of adding sand to the beaches. Sand is dredged from the continental shelf & pumped onto the beach.

Miami Beach Before beach replenishment After beach replenishment

Alternatives to Artificial Barriers 15)The problem with beach replenishment is it is only a temporary solution (only lasts 2 -4 years) because sand will always be removed by longshore currents & storms.

Alternatives to Artificial Barriers 16)Another alternative to artificial barriers is relocation.

Summary 17)The coastal zone is a dynamic environment that results from a variety of natural processes, like waves, currents, tides, storms, multiple sources of sediment, rising sea level, & coastal development by humans.

Summary 18)It is an extremely important region economically because the majority of the human population lives within 50 miles of the coast

Summary 19)Unfortunately, human impact on the coast is increasing, interfering with natural processes, and producing unintended ill effects.

Migration of Assateague Island

Sources • http: //www. usm. edu/marine/mar 151/MAR_151_C hap_11 b. html • http: //www. kqed. org/w/coastalclash/armoring. html • http: //www. glerl. noaa. gov/seagrant/glwlphotos/Mic higan/images/Mc. Kinney/mckinney 04. jpg • http: //www. geol. ucsb. edu/faculty/sylvester/UCSB_ Beaches/groins. html