MEAN HIGH WATER


A project documenting
Sea Level Rise & Flooding
in the South Carolina Lowcountry



01 OVERVIEW ︎︎︎
02 LATEST ︎︎︎   
03 ARCHIVE ︎︎︎
04   NEWSLETTER  ︎︎︎
05 RESOURCES ︎︎︎

ABOUT
Mean High Water (MHW) is a project documenting the impacts of sea level rise 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%.

This project was started by photographer and engineer Jared Bramblett in 2020. It is intended to be an evolving and collaborative documentation of the impacts of rising seas and how communities are adapting to them. 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.


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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.

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)

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 11/9/2021

REFERENCES

1Tidal Benchmark Station - Charleston, Cooper River Entrance, SC - Station ID: 8665530
This is the homepage for the Charleston Tidal Benchmark, which serves as the main tide gauge referenced for tide levels in the Charleston region. The tidal datums (e.g. MLLW, MHW, MHHW) for Charleston are presented here. Lunar tide levels predictions can be found here, and the database of historic tide levels can be accessed here.

2NWS Coastal Flood Event Database
This is a database maintained by the National Weather Service Charleston that tracks coastal flooding in Charleston and Savannah. It is referenced often throughout this site,  particularly when discussing the number of coastal floods that have occurred in Charleston Harbor.

3Advanced Hydrologic Prediction Service, Charleston, SC
Forecasts for water levels at the tidal bench mark based on meteorological predictions are presented here.

A Drought with Increased Flooding?

June 12, 2022

Tidal Flooding on Washington Street, Charleston

So far, the Charleston region has seen been 9.5 and 13 inches of rain this year, which is about 5” below average. There were some isolated areas of urban stormwater flooding during a moderately heavy rain last Thursday, but overall, there haven’t been significant occurences of stormwater flooding so far in 2022.

2022 NWS Climate Plots for the Charleston Area

It’s a different story when it comes to tidal flooding. In fact, from January to May of this year, we saw 22 tidal floods (tides exceeding 7’ on the mean lower low water datum) in Charleston Harbor, which sets the record for the most observed over the first five months of a year. 2019, which is the most active year for tidal flooding on record, saw 19 tidal floods over the same period. We also saw eight tidal floods in January and nine tidal floods in May, which are records for each of those months. It’s the first time that we’ve set two monthly records during the first half of a year over the period of record (1921 - 2022).
Tidal Floods, January through May (source: NWS Coastal Flood Event Database)

It’s a similar story with moderate tidal flooding (tides exceeding 7.5’ MLLW). Six of the 22 tidal floods reached this threshold, which is also a record for the first five months of a year. Due to astronomical influences associated with the upcoming full moon and perigee, we are currenlty in a coastal flood advisory, so the rate of tidal flooding does not appear to be slowing. 
© 2021