Sunday, June 18, 2017

New Paper by Billy Sweet and colleagues

2016 State of U.S. High Tide Flooding and a 2017 Outlook 

William V. Sweet1 , John J. Marra2 , Gregory Dusek1

National Oceanic and Atmospheric Administration’s Center for Operational Oceanographic Products and Services1 and National Centers for Environmental Information2 Summary 

The number of days with high tide flooding in 2016 was above the local flood‐frequency trend at the majority of the 28 locations examined (more than half of the trends are accelerating in time). Three all‐ time records for annual‐flood days were either tied (Key West, FL) or broken (Charleston, SC; Savannah, GA). If an El Nino develops this coming year (May 2017 ‐ April 2018) as model guidance suggests is possible, the frequency of daily floods may be compounded relative to long‐term trends, upwards of 25% or more at several U.S. West and East Coast locations.

Thursday, February 9, 2017

Sea Level Rise for Hampton Roads 2016

Sea Water Levels at Sewells Point, VA

With the end of the year, it is a good time to recap the data we have on flooding events and sea level rise for the Hampton Roads region. 

Hourly Data at Sewells Point

Average Annual Sea Level at Sewells Point

Because this is hourly data it is highly variable. Here is the annual average of the hourly data from Sewells Pt. 

There is considerable interannual variability caused by El Nino like processes in the global ocean that affect our local sea level.

10 year moving average at Sewells Point

We can take a 10 year moving average of the annual average to smooth out the interannual variations to get a better view of the long term trend.

The long-term average rate of increase is about 0.3 meters per 70 years (approximately) or 0.4 meters per century or about 1.5 feet per century. Note this is the running 10-year average so the first 10 years are truncated (the 1938 value is the average of the past 10 years). 

Hours per year of 'Nuisance Flooding'

The top panel shows the hours per year that water levels at Sewells Point were above the NWS defined nuisance flood level of 0.53 m above MHHW.

The lower panel shows the hourly Sewells Point water level. The solid horizontal line shows 0.53 m - the nuisance flood level. Sea level is rising causing there to be more nuisance flooding hours.

Return Period of Flooding Events

Blue line - Now - A one-meter flooding even occurs about every 3-4 years. A 1.4 meter flooding event occurs about every 33 years now.

Red line - 2050 with 0.5 m (1.5 feet) sea level rise - If sea level rises 0.5 meters as expected by 2050 a one-meter flooding event will be every year or more often and a 1.4 meter flood every 2 to 3 years.

The way to interpret this that flooding events that occurred once during a Hampton Roads resident's lifetime will occur several times during their children's.

Rate of Sea Level Rise

NOAA sea level trend

Quoting the NOAA site  (Link to NOAA Site)
The mean sea level trend is 4.59 millimeters/year with a 95% confidence
interval of +/- 0.23 mm/yr based on monthly mean sea level data from
1927 to 2015 which is equivalent to a change of 1.51 feet in 100 years."
More plots of interannual and seasonal trends are at the NOAA website.

The Past Year - 2016

Here are the Sewells Pt plots for the past year

I've labeled the major storm events. Note I'd like to know what the early May event was called.

2016 compared to other years

Each line is the average monthly temperature for a year. The heavy line is the monthly average data from 2016. Month months in 2016 had near record high average levels at Sewells Point.

You will notice that the highest water levels during any year are often in September. This is because the ocean waters are warmest then and they have expanded - making sea level higher. This is a seasonal effect.

Florida Current Transport

Over the past few years it has become evident that sea level in Hampton Roads is to some extent related to the strength of the Gulf Stream or the Florida Current. (They are the same. It is called Florida Current off Florida). You will note how it varies.

The reduced transport in early October coincided with Hurricane Mathew when is slowed over the Florida Current and apparently the southward winds slowed the Current. More on this from a paper Tal Ezer submitted. 

How this measurement is made can be found at Link to NOAA Florida Transport

Thursday, April 21, 2016

Urban resilience framework for Norfolk, VA -

A new report on Norfolk relevant to many coastal cities LINK

Here is the abstract:

The same water that makes Norfolk, VA an ideal home for international ports and naval installations is also increasingly flooding large parts of the city and the surrounding Hampton Roads region. This report describes the development of a process to analyze the resilience of urban regions to the shocks and stresses that those cities care about, and applies this process to address flooding in Norfolk and Hampton Roads. The goal is to provide Norfolk city officials and regional asset owners with actionable information to plan the infrastructure improvements that will most greatly enhance the region’s resilience to flooding. Results suggest that there are wide-ranging impacts of a major acute flooding event beyond the Hampton Roads region. A single four-day, 100-year flood event in Hampton Roads would cause on the order of $355-606 million in detrimental impacts to global production, with greater impacts occurring in the future as net sea levels rise. This report highlights the infrastructure behaviors, interdependencies, and the economic analyses that determine these impacts.

Wednesday, December 16, 2015

Unified Sea Level Rise Projection for SE Florida

Summary from the Report  LINK

The Work Group recommends the use of the NOAA High Curve, the USACE High Curve (USACE, 2015) and the median of the IPCC AR5 RCP8.5 scenario (IPCC, 2013) as the basis for a Southeast Florida sea level rise projection for the 2030, 2060 and 2100 planning horizons. In the short term, sea level rise is projected to be 6 to 10 inches by 2030 and 14 to 26 inches by 2060 (above the 1992 mean sea level). Sea level has risen 3 inches from 1992 to 2015. In the long term, sea level rise is projected to be 31 to 61 inches by 2100. For critical infrastructure projects with design lives in excess of 50 years, use of the upper curve is recommended with planning values of 34 inches in 2060 and 81 inches in 2100. Sea level will continue to rise even if global mitigation efforts to reduce greenhouse gas emissions are successful at stabilizing or reducing atmospheric CO2 concentrations; however, emissions mitigation is essential to moderate the severity of potential impacts in the future. A substantial increase in sea level rise within this century is likely and may occur in rapid pulses rather than gradually.

The recommended projection provides guidance for the Compact Counties and their partners to initiate planning to address the potential impacts of sea level rise on the region. The shorter term planning horizons(through 2060) are critical to implementation of the Southeast Florida Regional 14 Climate Change Action Plan, to optimize the remaining economic life of existing infrastructure and to begin to consider adaptation strategies. As scientists develop a better understanding of the factors and reinforcing feedback mechanisms impacting sea level rise, the Southeast Florida community will need to adjust the projections accordingly and adapt to the changing conditions. To ensure public safety and economic viability in the long run, strategic policy decisions will be needed to develop guidelines to direct future public and private investments to areas less vulnerable to future sea level rise impacts.