**Session No. 3**

**Course Title: Coastal Hazards Management**

**Session Title: Sandy Shores and Barrier Islands**

**Author: Professor John J. Bruno, University of North Carolina at
Chapel Hill**

**Time: 30 minutes**

**Objectives**

3.1 Outline the dynamic geological processes that create sandy shores
and barrier islands

3.2 Outline the organisms and communities found on sandy beaches and
barrier islands.

3.3 Outline some ecosystem services of sandy beaches and barrier
islands.

3.4 Discuss some of the hazards to sandy shore communities.

**Scope**

This session introduces students to the geological and biological
aspects of barrier islands and sandy shore communities. As a foundation
session, the material is basic in nature, providing background
information in a predominantly lecture format, supported by PowerPoint
slides of the habitats and organisms found in the sandy shore
environment.

**Readings**

*Instructor and Student Reading:*

Bertness, M.D. 1999. *The Ecology of Atlantic Shorelines*. Sunderland,
MA: Sinauer, pp. 8-10; 301-311.

*Additional Background Reading:*

Pethick, J.P. 1986. *An Introduction to Coastal Geomorphology*. MA:
Edward Arnold.

Kaufman, W. and O.H. Pilkey Jr. 1983 . *The Beaches Are Moving: The
Drowning of America's Shoreline.* Durham, NC: Duke University Press.

####### General Requirements

The content of this session should be presented as a lecture, supported
by PowerPoint slides that illustrate some of the key concepts and
communities of sandy shores and barrier islands. This lecture can be
combined with the lecture presented in Session Four on estuaries and
estuarine habitats, as the two are logically linked.

The course preparers have organized the subject matter in Sessions Two
through Five to be presented as lecture with accompanying slides.
However, the instructor may choose to canvass the class to discover if
any students have a background in zoology, biology or ecology, in which
case further in-depth discussion of the material may be encouraged.

**PowerPoint Slides:**

**PowerPoint** **3.1** Core Banks: A North Carolina Barrier Island

**PowerPoint** **3.2** Dune Blow Out

**PowerPoint** **3.3** Barrier Island and Estuary

**PowerPoint** **3.4** Estuarine Habitats created in part by Barrier
Islands

**PowerPoint** **3.5** Sand Dune Plant Community

**PowerPoint** **3.6** Wild Barrier Island Horses

**PowerPoint** **3.7** Barrier Island Zonation

**PowerPoint** **3.8** Barrier Island Zonation

**PowerPoint** **3.9** Sand Dune Plant Community and Maritime Forest

**PowerPoint** **3.10** Sandy Beach/Barrier Island Development

**PowerPoint** **3.11** Sandy Beach/Barrier Island Development

######## **PowerPoint** **3.12** Sandy Beach/Barrier Island Development

**PowerPoint** **3.13** Sandy Beach/Barrier Island Development

#### 

#### **Objective 3.1 Outline the dynamic geological processes that create sandy shores and barrier islands.**

**Requirements:**

The contents should be presented as lecture, supported by PowerPoint
slides.

The following slides will be used during this Objective:

**PowerPoint** **3.1** Core Banks: A North Carolina Barrier Island

**PowerPoint** **3.2** Dune Blow Out

**PowerPoint** **3.3** Barrier Island and Estuary

**PowerPoint** **3.4** Estuarine Habitats created in part by Barrier
Islands

**Remarks:**

###### [Definitions and geographic distribution of sandy shores and barrier islands]{.underline}

-   **A beach** is an *"aggregation of unconsolidated sediment, usually
    sand, that covers the shore".*

-   **Sandy shorelines and beaches** are found throughout **tropical and
    temperate regions** of the world, especially in locations with high
    sediment input from rivers and little or no glacial scouring, which
    can scrape away costal sediments.

-   **Barrier islands** are generally long, thin islands of beach, sand
    dunes, and vegetation that usually run parallel to the mainland, 50
    m to 20 km offshore.

> **\[PowerPoint 3.1 Core Banks: A North Carolina Barrier Island\]**

-   They usually form **chains**, separated by **channels** created by
    storms and maintained by tidal flux.

-   Barrier islands are especially **common on coastlines with wide
    coastal plains and continental shelves.**

    -   There are 10,765 km of barrier islands in North America,
        fringing 18% of the coastline.

    -   Barrier islands are especially common on the gulf and east
        coasts of North America below Boston.

    -   Florida has 533 km of barrier islands and Alaska has 1266 km.

##### [Dynamics of sandy shores and barrier islands]{.underline} 

-   The shape and location of beaches and barrier islands are **highly
    dynamic** and constantly modified by storms, winds, waves, tides,
    currents, and vegetation.

-   **Beach slope** is a fundamental geological property of beaches and
    varies greatly among beaches and seasons.

    -   **Beach slope** is complex, but is thought to be controlled in
        part by **sediment size** (cobble and shingle beaches are often
        steeper than sand beaches) and **wave height,** **angle, and
        size**.

        -   **Steeper waves** are thought to **create flatter beaches**
            by eroding sediment off the beach and depositing it on an
            offshore sand bar. This profile is often referred to as a
            **"winter beach".**

    -   **Blow outs** are portions of a sand dune that are altered by
        wind.

> **\[PowerPoint** **3.2** **Dune Blow Out\]**

-   **Washover fans** are fan shaped depositions of sediment on the
    landward side of a barrier island created by waves rushing over the
    island during storms.

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-   Barrier islands migrate landward naturally in a natural process
    called **barrier island rollover**. This is a complex response to
    sea level rise and the deposition of sediments on the coastal size
    of the island.

    -   The **rate of island migration varies** but can exceed 100 meter
        per century.

    -   **Evidence** of barrier island rollover on current exposed
        seaward beaches is the **peat of former marshes** and **trunks
        of trees** left from estuarine marshes and terrestrial and
        island forests.

-   **Major storms and hurricanes** frequently **reshape barrier islands
    and beaches** and **close old channels and inlets** to the estuary
    and **create new ones**.

    -   The length and shape of **spits, bars, and other features** are
        also **constantly changing**. A series of aerial coastal
        photographs would illustrate this point.

**[Classification of sedimentary emergent shoreline
features:]{.underline}**

-   **Bay barriers** are connected to the mainland at both ends.

-   **Spits** are attached to a beach or barrier island at one end and
    grow along the shore with the direction of the prevailing longshore
    current.

-   **Barrier islands** are not attached to the mainland at either end.

**[Role of barrier islands in the generation of estuaries]{.underline}**

-   Barrier islands play a **critical role** in the **geological
    generation of most estuaries.**

> **\[PowerPoint 3.3 A Barrier Island and Estuary\]**

-   The physical structure of the island creates **shoreward protected
    locations**. These areas are largely unaffected by ocean waves.

> **\[PowerPoint** **3.4 Estuarine Habitats created in part by Barrier
> Islands\]**

-   The presence of the barrier islands is **essential to many estuarine
    habitats and organisms**.

**Objective 3.2** **Outline the organisms and communities found on sandy
beaches and barrier islands.**

**Requirements:**

The contents should be presented as lecture, supported by PowerPoint
slides.

The following slides will be used during this Objective:

**PowerPoint** **3.5** Sand Dune Plant Community

**PowerPoint** **3.6** Wild Barrier Island Horses

**PowerPoint** **3.7** Barrier Island Zonation

**PowerPoint** **3.8** Barrier Island Zonation

**PowerPoint** **3.9** Sand Dune Plant Community and Maritime Forest

**Remarks:**

# **[Community Description]{.underline}**

####### Community inhabitants of sandy beaches and barrier islands

-   Barrier islands are fundamentally generated by the **deposition of
    sediments** and their subsequent transport by wind. However
    **coastal vegetation** also plays a critical role by stabilizing
    sediment, and ultimately building and shaping sand dunes.

> **\[PowerPoint** **3.5 Sand Dune Plant Community\]**

-   **Small plants** (e.g. beach rocket) that live just above the high
    tide mark are often responsible for creating **embryo dunes** or in
    some cases, facilitating their grow.

-   These **plants trap sediment**, by slightly reducing wind velocity.
    Sediment deposition build up a small dune, the plant grows, and a
    positive feedback is initiated.

-   Embryo dunes can also be initiated by debris deposited at the high
    tide mark.

-   These dunes build vertically and are eventually **colonized by other
    plant species**, including dune-stabilizing grasses such as American
    dune grass (*Ammophila*).

-   The positive feedback between plant and dune growth generates a
    large dune, parallel to the shoreline called the **fore dune**.

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-   Barrier islands are also occupied by **insects, crabs, birds, and
    other animals**. Many species of birds nest on barrier islands, and
    use them temporarily during migration.

> **\[PowerPoint 3.6 Wild Barrier Island Horses\]**

####### [Barrier island plant community zonation]{.underline}

-   Gradients of wind, water, and sand dune age create a **horizontal
    stress gradient**, running from the high tide mark, to the
    terrestrial border, or estuarine edge in the case of a barrier
    island.

> **\[PowerPoint 3.7 Barrier Island Zonation\]**
>
> **\[PowerPoint 3.8 Barrier Island Zonation\]**

-   **Very few plant and animal** species can live on the exposed beach
    or in the **fore dune zone**, characterized by high winds and salt
    stress, low soil moisture, and limited soil nutrient and organic
    content.

    -   The fore dune zone is dominated by grasses, succulent plants,
        and sometimes cacti.

-   **Further from the ocean**, conditions improve and small shrubs and
    **less-tolerant plants dominate.**

-   Wind and salt-resistant trees generate a **maritime forest** at the
    rear of the dune community or barrier island.

> **\[PowerPoint** **3.9 Sand Dune Plant Community and Maritime
> Forest\]**

-   **Salt marshes** usually form behind the maritime forest on the
    landward side of the barrier island in the **intertidal zone** of
    the estuary.

####### 

####### [Sandy beach animals]{.underline} 

-   A **diverse community of invertebrate animals** lives within the
    sand on the beach including

    -   clams,

    -   ghost crabs,

    -   worms,

    -   snails, and

    -   shore birds that prey on them.

# **Objective 3.3** **Outline some ecosystem services of sandy beaches and barrier islands.** 

**Requirements:**

The content should be presented as lecture.

**Remarks:**

# 

# **[Ecosystem services of sandy beaches and barrier islands]{.underline}**

-   Sandy beaches provide countless **recreational and economic
    opportunities** (e.g., fishing and swimming) that generate enormous
    economic activity from residents and tourists.

-   Barrier islands **reduce erosion** and **mitigate storm impacts** to
    the mainland coast.

-   Barrier islands **create protected estuaries and lagoons**,
    facilitate the presence of foundation species and estuarine
    habitats, and are thus indirectly responsible for the ecosystem
    services provided by estuaries.

# **Objective 3.4 Discuss some of the hazards to sandy shore communities.**

**Requirements:**

The contents should be presented as lecture, supported by PowerPoint
slides.

The following slides will be used during this Objective:

**PowerPoint** **3.10** Sandy Beach/Barrier Island Development

**PowerPoint** **3.11** Sandy Beach/Barrier Island Development

######## **PowerPoint** **3.12** Sandy Beach/Barrier Island Development

**PowerPoint** **3.13** Sandy Beach/Barrier Island Development

**Remarks:**

# **[Hazards to sandy beaches and barrier islands]{.underline}**

-   **Coastal development** is significant threat to barrier islands and
    the communities that inhabit them.

> **\[PowerPoint** **3.10 Sandy Beach/Barrier Island Development\]**
>
> **\[PowerPoint 3.11 Sandy Beach/Barrier Island Development\]**

######## **\[PowerPoint 3.12 Sandy Beach/Barrier Island Development\]**

> **\[PowerPoint 3.13 Sandy Beach/Barrier Island Development\]**

-   The **loss of plant cover** increases **erosion** and **reduces dune
    develop**ment by eliminating the stabilizing function of plants.

-   Even human **foot traffic** can significantly reduce plant cover in
    the fore dune.

    -   In many coastal locations, town and county agencies **regulate
        beach access** and reduce paths through the fore dune that
        accelerate beach erosion.

-   Plant loss can be mitigated by **replanting** and other
    **restoration** techniques.

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-   **Increasing sea level rise** due to natural and anthropogenic
    factors (e.g., global warming) threatens barrier islands and beaches
    and most estuarine habitats.

    -   In locations **where net sea level rise exceeds net island and
        wetland accretion**, these coastal features and habitats will be
        **lost.**

        -   For example, in **Louisiana,** net sea level rise can reach
            a centimeter per year, and wetland loss is greater that 40
            km^2^ per year.

-   **Hurricanes** are natural but serious hazards to barrier islands
    and associated estuarine habitats.

    -   Hurricanes can dramatically erode beaches and barrier islands
        and deposit the sediment in the landward estuary, smothering and
        destroying estuarine habitats.

        -   *For example*, in **Louisiana,** barrier island erosion
            exceeds 20 meters per year.

    -   **Severe hurricanes** (e.g., Andrew) have especially striking
        effects on barrier islands and coastal beaches.

-   **Dams** capture sediment and **reduce sediment input** into the
    ocean that beaches depend on.

-   **Groins, jetties, breakwaters**, and other structures designed to
    capture sand, usually starve the downstream beach, **accelerating
    erosion**.

######### **[Beach renourishment]{.underline}**

-   Natural erosion, reduced sediment input, and impediments on barrier
    island rollover can reduce beach and dune width and area.

-   Beachfront homeowners and business owners in the tourism industry
    often **pressure local and federal governments to artificially
    renourish** beaches by dredging sediments from offshore or in the
    estuary.

    -   This solution is **highly controversial** and **temporary** as
        the new beach usually erodes away in a few months or years.

    -   The **sediment is often coarse** and not aesthetically appealing
        or comfortable to walk on.

    -   Furthermore, renourishment is **detrimental** to the inhabitants
        of the **community from which it was collected** as well as the
        birds and invertebrates that live on and in the beach.

    -   Beach renourishment is also very **expensive** and is usually
        paid for by a combination of local and federal funding.