Presentation is loading. Please wait.

Presentation is loading. Please wait.

COASTAL FEATURES Crenulate Bays

Published by Modified over 9 years ago

Similar presentations

Presentation on theme: "COASTAL FEATURES Crenulate Bays"— Presentation transcript:

1 COASTAL FEATURES Crenulate Bays
Formed by erosion between two non-erodible controls. Also known as log –spirals Culprits are wave angle, refraction and diffraction processes.

2 CRENULATE BAY One of the best known is Half Moon Bay in California

3 CRENULATE BAY Can fit with log spiral of the form (Yasso, 1965) D&D
Where r is distance form center θ is angular coord θ0 is reference value for r=r0 α controls rate at which radius increases.

4 CRENULATE BAY Effect of varying alpha

5 CRENULATE BAY Effect of varying r0, like varying wave angle
I love matlab!

6 CRENULATE BAY Can become a particularly bad problem when the sediment supply versus carrying capacity is small. Examples: throat of inlet. St George Inlet, FL Gray’s Harbor, WA cirp.chl.wes.army.mil

7 CUSPS Rhythmic features in the alongshore direction located on the foreshore. No agreement as to formation mechanism and maintenance Typical conditions: Steep foreshore Surging waves Shore normal waves Narrow wave spectrum Medium sand and up Looks like a crenulate bay

8 CUSPS Flow within them Kuenan (1948) observed alternating surges into and out of adjacent embayments LAND Bay Bay Bay Horn Horn Edge wave anti-node Edge wave node

9 CUSPS Flow within them Bagnold (1940) breaking bore flow piles onto horns and diverges forming to streams that pour into the embayment. Streams from adjacent horns merge and form offshore jet. Dean and Maurmeyer, 1980 Komar, (Bagnold, 1940)

10 HOW WHO CUSPS Formation Mechanisms (as compiled by D&D)
Inhomogeneities of foreshore material Johsnon, 1919, Kuenan, 1948 Hydrodynamic instabilities in swash Gorycki, 1973 Breaking Waves Cloud, 1966 Presence of rips Shepherd, 1963, Komar, 1971 Edge waves Escher, 1937, Komar, 1973, Guza and Inman, 1975 Intersecting synchronous wave trains Dalrymple and Lanan, 1972 Littoral drift instability Schwartz, 1972 Self organization Werner and Fink, 1993 Swash processes Dean and Maurmeyer, 1980

11 CUSPS Edge wave Trapped along the coast by refraction, for standing, get fixed alongshore periodicity Ledge Lcusp n is the mode number or number of zero crossing of the cross-shore profile So many modes, can usually find one that matches field spacing

12 CUSPS Edge wave Higher mode numbers damped by friction, subharmonic period most likely relevant Implying Tedge = 2Twave (Guza and Inman, 1975) Cusp spacing is one half the edge wave wave length. Suggests same flow pattern as observed by Kuenan, 1948, see next slide

13 CUSPS Edge wave: alternate filling of embayments Time t Time t+Tedge/2

14 CUSPS Self Organization
Numerical model for cusp generation based on simple laws for particle motion and sediment transport Begins with planar beach with small random perturbations Surprisingly not susceptible to changes in model coefficients Get the same current pattern as Bagnold observed.

15 CUSPS Swash Processes Probably similar to self-organization.
Cusp topography and swash tend to cause circulation cells that construct and accentuate cusps Requires wave period approximately equal to natural swash period assuming ballistic motion on a frictionless plane Where Vo is the initial swash velocity Cusp spacing from their model is proportional to the swash magnitude as Where ε defines the relief of the cusp feature and ξ is the maximum excursion length.

Download ppt "COASTAL FEATURES Crenulate Bays"

Similar presentations

WS 7.1, Page 21 1a) Strength of wind and fetch affect the size of waves. The stronger to wind, the larger the size of waves. The longer the distance over.

WS 7.1, Page 21 1a) Strength of wind and fetch affect the size of waves. The stronger to wind, the larger the size of waves. The longer the distance over.
Mechanical Waves and Sound

Mechanical Waves and Sound
Wave Dominated Coasts Objective: to examine some of the processes and characteristics active on a wave-dominated coast.

Wave Dominated Coasts Objective: to examine some of the processes and characteristics active on a wave-dominated coast.
Understanding coastal processes and problems to produce successful management solutions. A case study of Dawlish Warren. Dr. Chris Spencer University of.

Understanding coastal processes and problems to produce successful management solutions. A case study of Dawlish Warren. Dr. Chris Spencer University of.
Coastal Processes.

Coastal Processes.
HARD STRUCTURES Designed with erosion mitigation in mind Typically not coincident with placement of sand, but can be Can often have adverse effects on.

HARD STRUCTURES Designed with erosion mitigation in mind Typically not coincident with placement of sand, but can be Can often have adverse effects on.
Types, characteristics, properties

Types, characteristics, properties
Beaches and Coastal Environments of Washington Southern WA Coast – sandy beaches, spits, lagoons, sediment supply from Columbia River, northward longshore.

Beaches and Coastal Environments of Washington Southern WA Coast – sandy beaches, spits, lagoons, sediment supply from Columbia River, northward longshore.
Waves Energy can be transported by transfer of matter. For example by a thrown object. Energy can also be transported by wave motion without the transfer.

Waves Energy can be transported by transfer of matter. For example by a thrown object. Energy can also be transported by wave motion without the transfer.
 Currents that run along the western coast of the United States are _________________.  Currents that run along the eastern coast of the United States.

 Currents that run along the western coast of the United States are _________________.  Currents that run along the eastern coast of the United States.
Chapter 15 Section 2 By Suzanne Black, Nick Stratton, Jordan Henault, Emily O'Donnell, Bryan Perlak, Shayne McConnell.

Chapter 15 Section 2 By Suzanne Black, Nick Stratton, Jordan Henault, Emily O'Donnell, Bryan Perlak, Shayne McConnell.
BackwardForwardHomeExit BackwardForwardHomeExit I. What are the major processes operating along coasts? 1.1 What is wave generation? Download Flash Player.

BackwardForwardHomeExit BackwardForwardHomeExit I. What are the major processes operating along coasts? 1.1 What is wave generation? Download Flash Player.
The Dynamic Ocean Chapter 16.

The Dynamic Ocean Chapter 16.
GCSE Geography Unit 2 – Natural Environment Topic 1 – Coastal Landscapes Lesson Aims: Able to describe the characteristics of destructive and constructive.

GCSE Geography Unit 2 – Natural Environment Topic 1 – Coastal Landscapes Lesson Aims: Able to describe the characteristics of destructive and constructive.
Waves, beaches, & sand transport

Waves, beaches, & sand transport
CROSS-SHORE TRANSPORT

CROSS-SHORE TRANSPORT
Beaches and Coastal Environments of Washington Southern WA Coast – sandy beaches, spits, lagoons, sediment supply from Columbia River, northward longshore.

Beaches and Coastal Environments of Washington Southern WA Coast – sandy beaches, spits, lagoons, sediment supply from Columbia River, northward longshore.
Oceans Ocean Topography Physical Structure of the Ocean.

Oceans Ocean Topography Physical Structure of the Ocean.
Chapter 15 Section 2.

Chapter 15 Section 2.
Coastlines. Beaches and Coasts The coastal zone and beaches along the continental margin are among the most dynamic geologic setting on earth Human settlements.

Coastlines. Beaches and Coasts The coastal zone and beaches along the continental margin are among the most dynamic geologic setting on earth Human settlements.

Similar presentations

Ads by Google