MEAN HIGH WATER


Flooding & Sea Level Rise in the SC Lowcountry





ABOUT
Mean High Water (MHW) is a project documenting the impacts of sea level rise & flooding in and beyond the South Carolina Lowcountry. The title is in reference to the MHW tidal datum defined and maintained by the NOAA Center for Operational Oceanographic Products and Service.

The tides of Charleston Harbor and the Atlantic Ocean are increasingly encroaching into the natural and built environment of Charleston and the Lowcountry. The rate of increase in the number of coastal flood events is alarming. Approximately 45% of all coastal floods observed in Charleston Harbor from 1953 through 2020 have occurred since 2010. An average of 18.8 coastal floods occurred per year in the 1990s. In the 2010s, the annual average was 42.4 coastal floods2, an increase of over 200%.

MHW was started in 2020 by photographer and engineer Jared Bramblett. It is intended to be an evolving and collaborative documentation of the impacts of flooding. If you are interested in participating and submitting to the project, please reach out. All content on this site is copyrighted. If you are interested in using any content, please submit a request.


CONTACT
Jared Bramblett
jaredbramblett@gmail.com

︎ ︎ ︎  
All thoughts and opinions presented on this site are solely those of the author and are not necessarily those of any other organizations.


01    INDEX︎︎︎
02    CHARLESTON UNDER WATER ︎︎︎
03    LATEST/NEXT ︎︎︎
04    NEWSLETTER ︎︎︎
05    RESOURCES︎︎︎





RECORDS & STATISTICS
Charleston Harbor, Cooper River Entrance1

Coastal Floods (>7-ft MLLW)2
1.
2.
3.
4.
5.
89 (2019)
68 (2020)
58 (2015)
55 (2016)
46 (2017, 2021)

Major Coastal Floods (>8-ft MLLW)2
1.
2.
3.
4.
5.
7 (2020)
6 (2015)
4 (2021)
4 (2019)
3 (2018)

Peak Tide Crests (MLLW)3
1.
2.
3.
4.
5.
09/22/1989 - 12.52-ft (Hugo)
08/11/1940 - 10.23-ft (Unnamed)
09/11/2017 - 9.92-ft (Irma)
10/08/2016 - 9.29 (Matthew)
01/01/1987 - 8.81-ft 

26 of the 40 (65%) major flood tides on record have occurred since 2015.3

Statistics current as of 07/01/2022


REFERENCES

1Tidal Benchmark Station - Charleston, Cooper River Entrance, SC - Station ID: 8665530

2NWS Coastal Flood Event Database

3Advanced Hydrologic Prediction Service, Charleston, SC 

Hurricane Ian in Charleston

October 8, 2022

Hurricane Ian passed east of Charleston on September 30, ultimately making its 2nd US landfall between McClellanville and Georgetown as a Category 1 hurricane. The Charleston area experienced stormwater flooding, hurricane-force winds, downed trees, and power outages. However, we were relatively lucky (again) with the storm landing to our northeast. 

By Monday, September 26th, most of South Carolina was within the cone of the potential track. As the storm was existing Cuba on Tuesdsay, the path of the storm became clearer, and a tropical storm watch was issued for the area. On Wednesday, as Ian was approaching landfall in Florida, a tropical storm warning and hurricane watch was issued along the South Carolina coast. The center of the predicted path showed Ian making landfall to the southwest of Charleston, potentially putting us in the northeast quadrant of the hurricane where storm surge is typically worse.


The Coastal Emergency Risk Assessment (CERA) coastal models for the track of NHC Advisory 24 showed the potential for a storm surge resulting in a peak tide elevation (storm tide) of 9.12-ft (MLLW datum), which would have been the fifth highest tide on record in Charleston Harbor. As Ian was entering the Atlantic on Thursday, the CERA modeled surge impacts for NHC Advisory 28 became worse, predicting a peak storm tide of 10.68’ (MLLW), which would have been the 2nd highest on record for the Harbor behind Hurricane Hugo (12.52-ft MLLW). The map below on the right shows the areas of the peninsula that are at or below 10.68’ MLLW and vulnerable to inundation from projected the storm tide.


Even with approximately 24-hours prior to landfall, slight shifts in Ian’s track could result in significant changes to surge projections, and in this case, that’s ultimately what happened. However, the likelihood of significant impacts for the Lowcountry was still high. The photos below show preparations around the City on Thursday evening. 


NHC Advisory 31 released on Friday morning showed Ian’s path shifting east of Charleston, decreasing the probability of significant storm surge for the area. Unfortunately, it increased the surge forecast for Georgetown and the Grand Strand, which is ultimately where the most impactful surge occurred with Ian’s 2nd US landfall.  The impacts for Charleston were still significant, but the storm tide barely reached flood stage, topping out just above 7-ft MLLW.
NWS Advisory 31 (Fri 9/30)
It began raining early on Friday morning, and by 7 AM the intersection of King and Huger Streets was already closed due to flooding. The City had setup temporary pumps to help drain low areas around town, and one was located in the King/Huger intersection. While these size of pumps are not large enough to prevent flooding from heavy rains, they do help areas drain faster as rainfall subsides. There was an approximate two hour break in the rainfall between 7 and 9 AM, which allowed most of the low areas to drain and temporarily reopen to traffic.




The rainfall began again between 9 and 10 AM and lasted through mid-afternoon. High tide also occurred around noon, and while it barely reached flood stage, it still prevented stormwater drainage from being able to discharge. Significant flooding occurred across the peninsula as a result. The photos below show the impacts around the City during and just after the peak of the storm. 


By mid-afternoon the rain and winds had subsided, but many areas remained flooded, and trees were down across the City. Many neighborhoods had also lost power. The photos below show some of the post storm impacts as of Friday afternoon.  Overall, it seems like the Charleston Area got relatively lucky with this storm. Just like Hurricanes Matthew (2016) and Dorian (2019), we really dodged a bullet in terms of the severity of storm surge.

© 2022