Cfa Level 1
Desiderato Chouinard
There is not 100% confidence in the elevation data and/or mapping process. It is important not to focus on the exact extent of inundation, but rather to examine the level of confidence that the extent of inundation is accurate (see mapping confidence tab).
The four relative sea level rise (RSL) scenarios shown in this tab are derived from the 2022 Sea Level Rise Technical Report using the same methods as the U.S. Army Corps of Engineers Sea Level Change Curve Calculator. These new scenarios were developed by the U.S. Sea Level Rise and Coastal Flood Hazard Scenarios and Tools Interagency Task Force as input into the U.S. Global Change Research Program Sustained Assessment process and, Fifth National Climate Assessment. These RSL scenarios provide an update to the NOAA 2017 scenarios, which were developed as input to the Fourth National Climate Assessment.
Note: We do not show the low scenario, as it is a continuation of the current global trend since the early 1990s and has been determined to have a low probability of occurring by 2100. Furthermore, this scenario would be associated with low levels of risk even if it did occur.
Another important change from the 2017 scenarios is the exclusion of the extreme (2.5 meter) scenario. Based on the most recent scientific understanding, and as discussed in the IPCC AR6, the uncertain physical processes that could lead to much higher increases in sea level are now viewed as less plausible in the coming decades before potentially becoming a factor toward the end of the 21st century. A GMSL increase of 2.5 meters is thus viewed as less plausible and the associated scenario has been removed.
For almost all the scenarios, RSL rise is likely to be greater than the global average in the U.S. Northeast and the western Gulf of Mexico. In intermediate and low scenarios, RSL rise is likely to be less than the global average in much of the Pacific Northwest and Alaska. For high scenarios, RSL rise is likely to be higher than the global average along all U.S. coastlines outside Alaska.
A RSL-change adjustment to the current National Tidal Datum Epoch (1983-2001) will cause a minimal offset that may be needed for some applications. The USACE Sea Level Change Curve Calculator can correct for this offset.
The inundation areas depicted in the Sea Level Rise tab are not as precise as they may appear. There are many unknowns when mapping future conditions, including natural evolution of the coastal landforms (e.g., barrier island overwash and migration), as well as the data used to predict the changes. The presentation of confidence in these maps only represents the known error in the elevation data and tidal corrections.
Blue areas denote a high confidence of inundation, orange areas denote a high degree of uncertainty, and unshaded areas denote a high confidence that these areas will be dry given the chosen water level.
In this application 80% is considered a high degree of confidence such that, for example, the blue areas denote locations that may be correctly mapped as 'inundated' more than 8 out of 10 times. Areas with a high degree of uncertainty represent locations that may be mapped correctly (either as inundated or dry) less than 8 out of 10 times. For a detailed description of the confidence levels and their computation, see the methods document.
Predictions represent the potential distribution of each wetland type (see legend) based on their elevation and how frequently they may be inundated under each scenario. As sea levels increase, some marshes may migrate into neighboring low-lying areas, while other sections of marsh will change type or be lost to open water.
Note: We do not show the low scenario as it is a continuation of the current global trend since the early 1990s and has been determined to have a low probability of occurring by 2100. Furthermore, this scenario would be associated with low levels of risk even if it did occur.
The Social Vulnerability Index, which shows areas of high human vulnerability to hazards, is based on population attributes from Census 2010 (e.g., age and poverty) and the built environment. By looking at the intersection of potential sea level rise and vulnerable Census tracts, one can get an idea of how vulnerable populations might be affected by sea level rise. Dark red indicates tracts having a high vulnerability, and the lighter reds indicate decreasing vulnerability.
Click on a NOAA tide station icon in the map to see historical inundation events in flood days per year. The flood thresholds used in these plots are derived national flood thresholds from NOAA Technical Report NOS CO-OPS 086: Patterns and Projections of High Tide Flooding Along the U.S. Coastline Using a Common Impact Threshold. The derived thresholds used here provide a national definition of coastal flooding and impacts for quantifying and communicating risk. These thresholds may deviate from NWS impact thresholds which take into account local flood risk and are used to issue NWS coastal flood watches, warnings, and advisories.
The purpose of this map viewer is to provide federal, state, and local coastal resource managers and planners with a preliminary look at sea level rise and coastal flooding impacts. The viewer is a screening-level tool that uses best-available, nationally consistent data sets and analyses. Data and maps provided can be used at several scales to help estimate impacts and prioritize actions for different scenarios.
Sea level rise is caused primarily by two factors related to global warming: the added water from melting ice sheets and glaciers, and the expansion of seawater as it warms. The first graph tracks the change in global sea level since 1993, as observed by satellites.
The second graph, which is from coastal tide gauge and satellite data, shows how much sea level changed from about 1900 to 2018. Items with pluses (+) are factors that cause global sea level to increase, while minuses (-) are what cause sea level to decrease. These items are displayed at the time they were affecting sea level.
This seemed like a great starting point for our user trust system. Thus, Discourse offers five user trust levels. Your current trust level is visible on your user page, and a summary of all trust levels within your community is presented on your dashboard.
Every new user gets a welcome PM mentioning the trust system and linking to this blog post, explaining that new users may be temporarily limited for safety reasons. They are also invited to start an optional interactive training conversation with discobot.
Upon transition to trust level 3, users are sent a longer form PM describing their new abilities and inviting them to the lounge category to meet their fellow TL3 community members. This PM also links here to this blog post.
(It's also worth mentioning that Discourse starts in "bootstrap mode" where the first 50 users who sign up are automatically granted TL1, and daily digests, to promote growth of the community via early adopters.)
At Discourse, we believe reading is the most fundamental and healthy action in any community. If a new user is willing to spend a little time reading, they will quickly be promoted to the first trust level.
Regulars are the backbone of your community, the most active readers and reliable contributors over a period of months, even years. Because they're always around, they can be further trusted to help tidy up and organize the community.
All of the above criteria must be true to achieve trust level 3. Furthermore, unlike other trust levels, you can lose trust level 3 status. If you dip below these requirements in the last 100 days, you will be demoted back to Member. However, in order to avoid constant promotion/demotion situations, there is a 2-week grace period immediately after gaining Trust Level 3 during which you will not be demoted.
Leaders are regulars who have been around forever and seen everything. They set a positive example for the community through their actions and their posts. If you need advice, these are the folks you turn to first, and they've earned the highest level of community trust, such that they are almost moderators within the community already.
We believe this trust system has been a success so far, as it leads to stronger, more sustainable communities by carefully empowering members, regulars, and leaders to curate and lead their own communities. It's one of the key community features that sets Discourse apart from the rest. But like everything else in Discourse, the trust system is evolving over time as we gain more experience with more communities. We'll continue to update this post with any changes.
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Long-term sea level rise will affect the extent, frequency, and duration of coastal flooding events. High-tide flooding events that occur only a few times a year now may occur once a month, or once a week in the coming decades. These same water level changes may also increase coastal erosion and groundwater levels. Elevated groundwater levels can lead to increased rainfall runoff and compromised underground infrastructure, such as public utilities, septic systems, and structural foundations. Higher water levels also mean deadly and destructive storm surges, wave impacts, and rainwater are unable to drain away from homes and businesses.
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