the foreshore - the area most influenced by the high and low water marks and breaking waves. the backshore - submerged only during the highest tides and severest storms. the berm – the high point on the beach; the backshore-foreshore boundary. It changes seasonally. Landforms and terminology in coastal regions

Berm Beach face Notch Wave-cut bench Longshore bar

Light versus heavy wave activity Light wave activityHeavy wave activity Berm/long- shore bar Berm grows and longshore bars shrink Longshore bars grow and berm shrinks Wave energyLowHigh Time spanLongShort CharacteristicsSummertime beach: sandy, wide berm, steep beach face Wintertime beach: rocky, thin berm, flattened beach face

Summertime and wintertime beach conditions Summertime beachWintertime beach

Movement of sand on the beach Movement parallel (↔) to shoreline –Caused by wave refraction (bending) –Each wave transports sand either upcoast or downcoast –Huge volumes of sand are moved within the surf zone –The beach resembles a “river of sand”

Erosion Deposition Human Development

Longshore current and longshore drift Longshore current = zigzag movement of water in the surf zone Longshore drift = movement of sediment caused by longshore current

Features of erosional shores Headland Wave-cut cliff Sea cave Sea arch Sea stack Marine terrace

Headland Eastern tip of Oahu

Wave-cut Cliff Ka‘ula

Sea Cave w/collapsed roof Na Pali Coast, Kauai

Sea stack (collapse of sea arch) Sea arch Puu Pehe (Sweetheart Rock) on the island of Lanai. Chain of Craters Rd., HI

Sea Arch and Sea Stack

Marine Terrace Haunama Bay

Features of depositional shores Spit Bay barrier Tombolo Barrier island Delta

Spit

Barrier Bay

Tombolo Poipu Beach Park Kauai

Formation of barrier islands Sea level rose after the last Ice Age Caused barrier islands to roll toward shore like a tractor’s tread

Barrier Islands Features: 1.Ocean beach 2.Dunes 3.Barrier flat 4.High salt marsh 5.Low salt marsh 6.Lagoon

Barrier Beaches Red Sands Beach, Maui

Barrier Islands

Deltas Feature: Triangle deposit of sediment Mississippi Delta Nile River Delta

Features of Submerging Shorelines Changes in Sea Level: Tectonic movement Isostatic adjustment Worldwide (eustatic) changes in sea level Ice ages Global warming

Composition of Beach sand in Hawaii: Coral Shells Sponge spicules Calcareous algae Volcanic particles Shark teeth

White Sand Beach

Black Sand Beach Big Island

Green Sand Beach Big Island Mahana Bay, HI

Red Sand Beach Maui

1.An abundant supply of loose sand in a region devoid of vegetation 2.A wind energy source sufficient to move sand grains 3.A topography whereby sand particles lose their momentum and settle out

Vegetated dune, Kanaha, Maui. Naupaka shrub and 'aki'aki and pohuehue (with purple flowers) ground cover at center, 'aki'aki (sparse ground cover) in background.

Close up of 'aki'aki. Photo from JOHNSTONE, Close up of 'akulikuli. Photo from JOHNSTONE, Close up of pohuehue, Honokahua, Maui Common name: beach morning glory

Sea-Level Rise Wave/Current Action Coastal Erosion Sediment Deficiencies Sand mining Dune grading Sand impounding (behind shoreline structures) Water quality degradation Harbor/navigational channel construction

Types of hard stabilization Hard stabilization perpendicular to the coast within the surf zone: –Jetties—protect harbor entrances –Groins—designed to trap sand Hard stabilization parallel to the coast: –Breakwaters—built beyond the surf zone –Seawalls—built to armor the coast

Shoreline Hardening: Groin

Shoreline Hardening: Jetty

Shoreline Hardening: Breakwater Magic Island is a peninsula shooting off from Ala Moana Park. The beach is protected by a man-made breakwater that cuts off the action of the surf while allowing enough water circulation to keep the salt water fresh and clean.

Shoreline Hardening: Seawall Waikiki Beach from the Halekulani Hotel.

Lanikai

Beach Replenishment Kohio Beach 10,000 cubic yards of sand pumped from off shore

Beach Replenishment Kohio Beach

Beach Replenishment Kohio Beach

Before After Beach Replenishment Kohio Beach

Beach Replenishment Kohio Beach Before After

Reasons to Protect Hawaii's Beaches Multi-billion dollar visitor economy They are critical in flood and erosion prevention They are a part of Hawaii's culture and heritage. Beaches and dunes are important elements of our shoreline environment and are critical to the health of the coastal marine ecosystem.

Inquiry 1.Types of hard stabilization include:_____. 2.Is there a way to slow down erosion without using hard stabilization? 3.Beach sand from Hawaii is composed of _____. 4.How is a sea stack formed? 5.What are some key characteristics of plants living on dunes?