MEAN HIGH WATER


A project documenting
Sea Level Rise & Flooding in the Lowcountry


01 OVERVIEW ︎︎︎
02 LATEST ︎︎︎   
03 ARCHIVE ︎︎︎
04 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 (2019)
3 (2018)
2 (2009, 1947)

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 

22 of the 36 (61%) major flood tides on record have occurred since 2015.3

Statistics current as of 3/31/2021

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.

2NOAA Coastal Flood Event Database
This is a database maintained by the NOAA Coastal Services Center 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 Center, Charleston, SC
Forecasts for water levels at the tidal bench mark based on meteorological predictions are presented here.

8.13-FT King Tide

15 NOVEMBER 2020 Updated Jan 2021 - Jared Bramblett


The tide in the Charleston Harbor peaked at 8.13-feet mean lower low water (MLLW) on Sunday, November 15, 2020 at 7:54 AM.
  • It was the 2nd highest tide 0f 2020.
  • It was also the 6th ‘major’ coastal flood (tide > 8-ft MLLW) of 2020, which tied 2020 with 2015 for most major flood events in a year. 2020 ended up with one additional major flood tide, setting the record for most in a year.
  • So far, there have been 61 coastal floods this year, which is the second most observed in a year. It appears 2019’s record of 89 coastal flood events is safe. 2020 ended with 68 coastal floods.

This should not feel normal, but it does. There have only been 32 tides that have exceeded the 8’ threshold since 1953. Seven of them have occurred in 2020, and 22 have occured since 2015. It’s surreal and unnerving to see the tides quietly flood streets several blocks inland from the Ashley River. The photos presented here are from the Westside and Gadsden Green communities on the Ashley River side of the Charleston Peninsula.

The below left map presents an elevation analysis of the area depicting elevations below the tide crest of 8.13-feet MLLW. It should be noted that water surface elevations decrease the further the water intrudes inland. So, while the tide level harbor crested at 8.13-feet MLLW, it did not reach that elevation inland. As an example, the map indicates that President Street would be significantly flooded, but the actual limits of the flooding were not that large. 

The map on the right presents the same elevation analysis projected over the 1919 USGS Quad Map of the area. Notice how most of the area that was flooded used to be tidal creek and marsh.









© 2021