Where Did My Beach Go?

Topic(s):

Hydrosphere, Lithosphere, Oceans

Scenario:

"The sand dunes are gone. So is the salt grass. The house now sits at the water's edge, stranded like a beached whale. A whale on stilts, that is." Shifting Ground Website

Approximately 235 acres (more than 181 footballs fields) of land along the Texas gulf coast are lost annually to erosion. In recent years Surfside Beach, a village approximately 60 miles south of Houston, has been particularly hard hit losing up to 9 ft of beach per year. As erosion progresses the shoreline moves inland and what was once private beach front property is converted to public beach. Several houses have already been lost to the ocean and other homeowners are being forced to relocate because Texas law does not allow houses on open access beaches.

Sediment generated by weathering of rocks and shells is transported to beaches by rivers, wind, waves, and currents. These same sediment transport processes can also be agents of erosion, carrying sand away from beaches. The flux of sediment to and from beaches constantly changes as weather events and tidal cycles influence the strength and direction of the wind, waves, and currents.

Coastal erosion is a continuous and natural process, but human activities can accelerate the rate of erosion. Globally, land along coastlines is being flooded and erosion is progressing further inland as sea level rises due to anthropogenic climate change. This problem is exacerbated in areas, like those along the U.S. Gulf Coast, where the land is subsiding as vast amounts of water and oil, which partially support the overlying sediments, are removed for human consumption.

Many communities around the world are facing problems with coastal erosion, rising sea level, and land subsidence. However, at Surfside Beach, the problems have been made particularly severe by human modifications to rivers and coastlines. In 1929, the U.S. Army Corps of Engineers diverted the mouth of the Brazos River 6.5 miles to the south to keep sediment from filling up the ship harbors and canals in the City of Freeport. Prior to this diversion, Surfside Beach was located on the stable river delta east of Freeport. With the river now transporting its sediment load further south, this original delta has been starved of its sand supply and erosion has outpaced deposition. Additionally, jetties, groins and seawalls constructed to prevent erosion at other locations have interfered with the longshore transport of sand, further reducing the supply of sediment to Surfside Beach.

The economic impacts of coastal erosion and land subsidence are as significant as those from hurricanes. In the U.S. coastal erosion causes billions of dollars of damage every year. Because engineering attempts to modify sediment transport (river diversions, sea walls, groins, etc.) can actually exacerbate the problem, the best approach for minimizing the damage due to coastal erosion is to prohibit building in low lying coastal areas.

Task:

Basic task: Your group has been contacted by a group of homeowners whose houses are threatened by the ongoing erosion at Surfside Beach. The homeowners have requested that you investigate the situation and make recommendations for how to minimize their losses due to the erosion.

Comprehensive task: You have been hired by the Village of Surfside Beach to help them develop a long term plan for dealing with coastal erosion. Specifically, the Village wants you to 1)estimate how much erosion has occurred in the last 50 years, 2) estimate how much erosion will likely occur in the next 50 years, 3) provide an estimate of where the shoreline will be in 50 years, and 4) make recommendations for minimizing property damages and economic losses due to erosion. In order to help you get started, the Village has given you existing maps, data and reports that address the coastal erosion problem. You can access these resources at the Texas General Land Office and at Texas Coastal Geology.

Date: 4/27/2010

Scenario Images:

When Brooks and Merry Porter bought their home a quarter-century ago, sand dunes stood between their house and the beach. But coastal erosion, partly due to government projects such as dam and jetty-building, has put the shoreline at their front step. Source: from National Public Radio

Map showing coastal areas within the United States where coastal erosion takes place. Source: from USGS

Interactions of factors that influence land loss. Modified from Morton (1977). Source: from USGS

Sand is transported alongshore by currents formed when waves strike the beach at an angle. Sand is also carried along the shore in a zigzag pattern by waves rushing onto the beach and back into ocean. Source: from USGS

This series of images depicts erosion and accretion along a jetty. (From Washington State Department of Ecology, 2004; modifications by Betsy Boynton,U.S. Geological Survey. Source: from USGS

Resources:

An Overview of Coastal Land Loss: With Emphasis on the Southeastern United States (Cycle A)
This USGS report provides an overview of coastal erosion. It has a strong emphasis on physical processes and interactions among various spheres.

Audio slideshow about erosion at Surfside Beach (Cycle A)
This audio slideshow contains interviews with homeowners whose houses have been impacted by the severe beach erosion at Surside Beach.

Coastal erosion - from Oceanography in the 21st Century: an online textbook (Cycle A)
This website contains an overview of coastal erosion processes and some case studies.

What is Coastal Erosion? (Cycle A)
This primer on coastal erosion covers both natural and anthropogenic causes of coastal erosion.

Beach erosion (Cycle B)
Topics covered in this Why Files feature article include: the nature and extent of beach losses, the role of beaches in protecting coasts, some measures -good and bad- to prevent coastal erosion, predicted effects of global warming and sea-level changes on beaches and the impact of melting ice sheets on global ocean volume.

Severe Beach Erosion at Surfside, Texas Caused by Engineering Modifications to the Coast and Rivers (Cycle B)
This consultant's report provides an overview of the history of Surfside, Texas and discusses the causes for the ongoing severe beach erosion.

With Climate Change Comes Floods (Cycle B)
This NPR news story describes how global warming causes sea level rise and discusses the impact of sea level rise on coastal areas.

Houston-Galveston, Tx: Managing coastal subsidence (Cycle C)
This USGS report describes subsidence in the Houston area that is due to excessive pumping of groundwater and extractions of oil and gas.

U.S. Army Corps of Engineers Coastal and Hydraulics Laboratory (Cycle C)
This is the U.S. Army Corps of Engineers Coastal and Hydraulics Laboratory's Erosion Control website. Follow the links for information about beach nourishment, groins and other coastal structures.

Sample Investigations:

Coastal geologic materials (Cycle A)
This is an interactive computer activity that describes the origins of coastal sediments.
Difficulty: beginner

Surfside Beach Shoreline Change Maps (Cycle A)
This Texas General Land Office website has eerial photographs depicting the erosion at Surside Beach.
Difficulty: beginner

Coastal geologic processes (Cycle B)
In this interactive computer activity, learners investigate the forces that help shape coastlines.
Difficulty: intermediate

Coastal wave mechanics visualizations (Cycle B)
This websites contains links to several QuikTime movies that illustrate the motion of waves and how waves and currents shape coastlines.
Difficulty: intermediate

Rising temperatures, disappearing coastlines (Cycle B)
This interactive graphic from NPR depicts how global warming could alter coastlines around the world.
Difficulty: beginner

Carolina coastal science (Cycle C)
This website contains several resources for educators including: case studies that can be used in inquiry based lessons, images that be used to stimulate classroom discussions, QuickTime videos depicting coastal processes, and a teacher's guide.
Difficulty: intermediate

Coastal erosion: Where's the beach? (Cycle C)
In this activity, learners graph beach profile data to investigate coastal erosion and sediment transport.
Difficulty: advanced

Standards:

• Science
  National Science Education Standards - Science Content Standards http://www.nap.edu/readingroom/books/nses/html/overview.html#content The science content standards outline what students should know, understand, and be able to do in the natural sciences over the course of K-12 education.
  • K-12 UNIFYING CONCEPTS AND PROCESSES
    The understandings and abilities associated with the following concepts and processes need to be developed throughout a student's educational experiences:
    • Evidence, models, and explanation
    • Constancy, change, and measurement
  • GRADES 5-8 CONTENT STANDARDS
    • Science as Inquiry (Std A)
      • Abilities necessary to do scientific inquiry
      • Understanding about scientific inquiry
    • Physical Science (Std B)
      • Motions and forces
    • Science in Personal and Social Perspectives (Std F)
      • Populations, resources, and environments
      • Natural hazards
• Geography
  Geography for Life: National Geography Standards, 1994
  • THE WORLD IN SPATIAL TERMS
    Geography studies the relationships between people, places, and environments by mapping information about them into a spatial context. The geographically informed person knows and understands:
    • How to use maps and other geographic representations, tools and technologies to acquire, process, and report information from a spatial perspective
  • PLACES AND REGIONS
    The identities and lives of individuals and people are rooted in particular places and in those human constructs called regions. The geographically informed person knows and understands:
    • The physical and human characteristics of places
  • PHYSICAL SYSTEMS
    Physical processes shape Earth’s surface and interact with plant and animal life to create, sustain, and modify ecosystems. The geographically informed person knows and understands:
    • The physical processes that shape the patterns of Earth’s surface
  • HUMAN SYSTEMS
    People are central to geography in that human activities help shape Earth’s surface, human settlements and structures are part of Earth’s surface, and humans compete for control of Earth’s surface. The geographically informed person knows and understands:
    • The characteristics, distribution, and migration of human populations on Earth’s surface
  • ENVIRONMENT AND SOCIETY
    The physical environment is modified by human activities, largely as a consequence of the ways in which human societies value and use Earth’s natural resources, and human activities are also influenced by Earth’s physical features and processes. The geographically informed person knows and understands:
    • How human actions modify the physical environment
    • How physical systems affect human systems