Protection from storm surge on 30A

[hi n dry]

According to the National Oceanic and Atmospheric Administration (NOAA), "The greatest potential for loss of life related to hurricane is from the storm surge, which historically has claimed nine of ten victims".

In fact, hurricane surge presents a greater risk to both life and property than hurricane winds. Coastal elevation maps published by the US Environmental Protection Agency (EPA) show that the Florida Panhandle, also known as the Florida Uplands, and specifically The Emerald Coast has some of the highest coastal elevations in the Southeast United States.

A comparison of 3 coastline maps produced by this project show the following:

The Beaches of South Walton are of Florida's Panhandle has primarily continuous high dunes and wide natural beach greater 30 meters wide.
http://pubs.usgs.gov/of/2004/1217/

The East Pensacola area of Florida's Panhandle has significant overwash terrace and few dunes. Overwash areas occur when storm waters exceed the elevation of the adjacent land and the ocean water flows onshore. Most of the beach width is greater than 30 meters of natural beach but there are a number of areas that are less than 30 meters wide.


The Galveston , Texas area has large coastal areas that are absent of protective dunes and have sporatic areas where the beach is less than 30 meters wide.

from article by D. Orr
CHECK OUT FOR FURTHER DETAILS:
http://www.uniquepanhandleproperties.com

[hi n dry]

This color coded coastal classification atlas shows view of Little Redfish Lake on the left(west) Grayton Beach(middle) and Seagrove Beach on right.

The dunes offer continuous protection from Grayton Beach State Park through all of Seagrove Beach until almost Eastern Lake. The elevation of the dunes gradually increase from Watercolors (dune elevation approx. 20 feet high) to Seaside (about 20 to 25 feet high) through Seagrove Beach where dune elevation exceeds 30 feet until just to the east of One Seagrove Place where elevations start declining as you get closer to Eastern Lake.

The areas of coastal lakes such as Little Redfish Lake, Alligator Lake, Grayton Beach,and Eastern Lake have vulnerable low elevation (7 to 10 feet above sea level) that could be overwashed (orange line) in a hurricane. The Gulf Trace dunes are continuous and about 10 to 20 ft high until you get closer to Alligator lake.

Note that low lying (with an elevaton below storm surge height) areas inland from dunes breached by a high storm surge and overwash coastal lake zones would be suseptible to storm surge flooding.

[bsmart]

According to the National Oceanic and Atmospheric Administration (NOAA), "The greatest potential for loss of life related to hurricane is from the storm surge, which historically has claimed nine of ten victims".

In fact, hurricane surge presents a greater risk to both life and property than hurricane winds. Coastal elevation maps published by the US Environmental Protection Agency (EPA) show that the Florida Panhandle, also known as the Florida Uplands, and specifically The Emerald Coast has some of the highest coastal elevations in the Southeast United States.

A comparison of 3 coastline maps produced by this project show the following:

The Beaches of South Walton are of Florida's Panhandle has primarily continuous high dunes and wide natural beach greater 30 meters wide.
http://pubs.usgs.gov/of/2004/1217/

The East Pensacola area of Florida's Panhandle has significant overwash terrace and few dunes. Overwash areas occur when storm waters exceed the elevation of the adjacent land and the ocean water flows onshore. Most of the beach width is greater than 30 meters of natural beach but there are a number of areas that are less than 30 meters wide.


The Galveston , Texas area has large coastal areas that are absent of protective dunes and have sporatic areas where the beach is less than 30 meters wide.
from article by D. Orr
CHECK OUT FOR FURTHER DETAILS:
http://www.uniquepanhandleproperties.com


That unsightly historic seawall feature has something to do with that--prevents the natural buildup of sand and growth of sea oats and other coastal vegetation.

[hi n dry]

The below is the aerial coastal classification view of Miramar Beach.
As you can see there are breaks in the dune barrier and the dune elevation is about 10 to 20 feet high .

For comparison: On 30A in Seagrove Beach the dune protection is continuous and over 30 feet elevation.

[hi n dry]

This aerial photo shows the coastal classification of Destin.
http://pubs.usgs.gov/of/2004/1217/images/destin/destin_sw_1500.jpg

Note that the protective dunes are not continuous like they are in Seagrove Beach.

The dune elevation in front of developed areas in Destin ranges from about 6 to 15 feet. The dunes at Henderson Park are at about 20 feet.

The dune elevation in Seagrove Beach on 30A exceeds 30 feet.

[hi n dry]

This aerial mapping shows Salt Creek and Mexico beach area.

http://pubs.usgs.gov/of/2004/1044/images/beacon_hill_ne/beacon_hill_ne-1500.jpg

The coastal dunes in this are are predominantly absent and at best discontinuous.

Coastal elevations along Mexico Beach/Salt Creek area range approximately from 7 to to 15 feet.

Note that Hurricane Katrina is estimated to have created storm surges of 15 to 35 feet depending on location.

It is also interesting that the shallower the coastal sea bottom the worse the storm surge. Waters rise more easily when there's less of it to push. The shallower waters in the general area of Mexico Beach therefore maybe conducive to storm surge.

[drsvelte]

Thanks for posting this info. I wasn't real pleased to see the data on Mirimar Beach though :blink: .

[hi n dry]

to drsvelt:
You are better off in Miramar Beach than Destin or most anywhere west for that matter. Plus you are also much better in Miramar than east of Panama City.
However,you should consider flood insurance in case you get a bad hurricane. You actually could get flooded from the Bay as well as from the Gulf.

[Paula]

Does anyone know how the elevation of much of 30A (the higher parts - 20 to 30 feet) compare to elsewhere in Florida. Are these areas considered some of the highest elevated locations in Florida? What parts of Florida have higher elevations? thanks.

[hi n dry]

The highest point in Florida is in Walton County: 345 feet.

To the best of my knowledge the highest elevation along the coast any where in Florida , the entire Gulf Coast of the US, and the Atlantic coast south of New Jersey is on Scenic 30A.

The highest coastal point on Scenic 30A is in the Blue Gulf Beach/ Blue Mountain area.

Look at the attached aerial coastal classification map. Note the first colored line inland along the beach; the segment of blue line designates the highest point at approximately 50 feet. However, note that most of the coastal elevations to the west of this point are primarily in the range of 5 to 20 feet with some isolated sections over 30 feet.

If you are looking for a property with good elevation you will need to know the specific elevation of that particular property. Scenic 30A has most of the highest elevation property available. However, there are some locations even on 30A which are vulnerable.

In fact in Seagrove Beach where most of the coastal elevations are over 30 feet there are some places as you move inland about 1/4 mile that are quite low and maybe vulnerable to flooding. For example, as you drive north from the beach past the Seagrove Village Market on 395 you will go down a “hill” or big dip before you get to the new Publix.

If you buy property anywhere on the coast get an official survey that includes the elevation.


Check out this web site to see the coastal classification of other areas.

http://coastal.er.usgs.gov/coastal-classification/


Also read the below excerpt which elaborates on the complexity of storm vulnerability :

“The potential storm vulnerability of a particular segment of coast depends on a number of variables including the storm characteristics and the land characteristics. ... The interaction between coastal storms and the shoreline is complex, and our present scientific understanding of this interaction is still limited; therefore, storm vulnerability cannot be quantified precisely. Despite the limitations, the map classifications and ground elevations presented in this report provide a basis for relative comparisons of storm vulnerability. “

Coastal Storm Vulnerability
http://pubs.usgs.gov/of/2004/1217/vulner.html

For this report, storm vulnerability refers to the potential impacts related to storm surge, waves, and associated currents. These storm processes cause beach and dune erosion, overwash, and onshore sediment transport. The storm vulnerability discussion does not consider potential property damage related to high wind and heavy rain. The potential storm vulnerability of a particular segment of coast depends on a number of variables including the storm characteristics and the land characteristics. The most important storm parameter used to evaluate storm vulnerability is the high water levels caused by high waves superimposed on the storm surge. The interaction between coastal storms and the shoreline is complex, and our present scientific understanding of this interaction is still limited; therefore, storm vulnerability cannot be quantified precisely. Despite the limitations, the map classifications and ground elevations presented in this report provide a basis for relative comparisons of storm vulnerability.

Natural or manmade features that dissipate wave and current energy or block the overland flow of storm water provide some protection to upland structures and reduce the storm vulnerability. For example, impact vulnerability for most storms is low where the beaches are wide, the natural dunes are several meters high and continuous along the beach, and the dunes are stabilized with vegetation. Storm vulnerability can also be reduced by engineering structures such as seawalls and riprap aligned parallel to the shore. Buildings that are not elevated above the ground can also prevent or reduce the inland transmission of waves if they are able to withstand the power of the waves and scouring caused by the currents. Conversely, houses that are elevated on pilings allow floodwaters to flow landward. Storm vulnerability is high for those areas where the beach is narrow, dunes are low and discontinuous, and dune vegetation is sparse. The presence of an overwash terrace is convincing evidence that the area has been submerged by storm waves in the past and is vulnerable to future storm impacts.

Another potential storm hazard on barrier islands is breaching of new inlets. Narrow barrier island segments that have elevations less than 2 m high and that are far from tidal inlets are the most susceptible to breaching by an extreme storm. This is because storm surges not only exceed the dune heights, they also exceed the adjacent lagoon level, creating a hydraulic head that incises channels across the narrow barrier (Morton, 2002). The moderately high dune elevations along the barriers of the northwestern panhandle coast of Florida have prevented the opening of new inlets. The most recent intense hurricane (Opal in 1995) eroded the dunes and constructed extensive washover deposits, but no new channels were opened.

continue to: Classification Summary

[aquaticbiology]

This aerial mapping shows Salt Creek and Mexico beach area.

http://pubs.usgs.gov/of/2004/1044/images/beacon_hill_ne/beacon_hill_ne-1500.jpg

The coastal dunes in this are are predominantly absent and at best discontinuous.

Coastal elevations along Mexico Beach/Salt Creek area range approximately from 7 to to 15 feet.

Note that Hurricane Katrina is estimated to have created storm surges of 15 to 35 feet depending on location.

It is also interesting that the shallower the coastal sea bottom the worse the storm surge. Waters rise more easily when there's less of it to push. The shallower waters in the general area of Mexico Beach therefore maybe conducive to storm surge.

I notice the major shift between the proper dunes, then the trashed dune system - gee, could that be development?
http://www.sowal.com/bb/attachment.php?attachmentid=724&stc=1&thumb=1

[hi n dry]

good observation! Thanks for pointing that out.
Development not only damages the protective dunes but interferes with natural beach renourishment.

What do you think about all this beach armouring and beach excavation?
In the process of installing these massive seawalls they are using heavy equipment to dig down into the under lying layer of the beach. This excavation brings up dirt and darker sand from under the white sand beach layer and that is being allowed to mix with and contaminate the white sand.

[Beachlover2]

:popcorn: :popcorn: :popcorn:

[aquaticbiology]

:popcorn: :popcorn: :popcorn:

like pulling the chain on a old 'tommy' cabinet!

You are soooo lucky I have to vacuum and I can't rehash all the retaining wall/geotube madness into a 4-page post, so here you go instead:

read this through and you will understand everything about coastal erosion, development, protection schemes and devices, determining the amount and 'ground truth' of coastal zone anaylsis, etc and what exactly is happening to our beaches over the long run. It is mainly carribean island based, but applies directly to nw florida coastal areas.

http://www.unesco.org/csi/pub/source/ero1.htm

"Coping with Beach Erosion is a practical guide for beach users, builders and homeowners as well as other coastal stakeholders. Written in a language and style accessible to the non-specialist, it provides expert advice concerning the dangers to consider when buying property and constructing houses, hotels etc. in erosion-prone beach areas. The question of how to conserve existing beaches is dealt with by demonstrating well tested shoreline protection and other management measures for current and potential erosion and accretion problems."

http://www.unesco.org/csi/pub/source/ero28b.gif

[Beachlover2]

Thanks for all the info you have provided - I feel the need to try to understand what we are doing to the future of your area - even if some attempts to change the situation go unheeded.

[hi n dry]

The attached aerial maps cover from Seaside to Seagrove Beach.
The highest elevation land on the map-above 30 feet- is approximately circled in yellow and extends from east side of Seaside through Seagrove Beach along Scenic 30A. Note that the elevation dips in the approximate area of The Hammocks subdivision along CR395.


There was a reason why the Old SeaGrove Beach area was chosen for an early settlement.

[aquaticbiology]

The attached aerial maps cover from Seaside to Seagrove Beach.
The highest elevation land on the map-above 30 feet- is approximately circled in yellow and extends from east side of Seaside through Seagrove Beach along Scenic 30A. Note that the elevation dips in the approximate area of The Hammocks subdivision along CR395.


There was a reason why the Old SeaGrove Beach area was chosen for an early settlement.

read this through and you will understand everything about coastal erosion, development, protection schemes and devices, determining the amount and 'ground truth' of coastal zone anaylsis, etc and what exactly is happening to our beaches over the long run. It is mainly carribean island based, but applies directly to nw florida coastal areas.

http://www.unesco.org/csi/pub/source/ero1.htm

"Coping with Beach Erosion is a practical guide for beach users, builders and homeowners as well as other coastal stakeholders. Written in a language and style accessible to the non-specialist, it provides expert advice concerning the dangers to consider when buying property and constructing houses, hotels etc. in erosion-prone beach areas. The question of how to conserve existing beaches is dealt with by demonstrating well tested shoreline protection and other management measures for current and potential erosion and accretion problems."

http://www.unesco.org/csi/pub/source/ero28b.gif

[aquaticbiology]

Thanks for all the info you have provided - I feel the need to try to understand what we are doing to the future of your area - even if some attempts to change the situation go unheeded.

minamina, hanaka! last post not meant for BL2 (I get it and I love the popcorn!), but for hi-n-dry.

this is what happens when you post from work.