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Frequently Asked Questions about

Our Coast, Our Future (OCOF)

Please click on a question to reveal the answer.

GENERAL

What is OCOF?

Our Coast, Our Future (OCOF) is a collaborative, user-driven project focused on providing San Francisco Bay Area coastal resource managers and planners locally relevant, online maps and tools to help understand, visualize, and anticipate vulnerabilities to sea level rise and storms.

Project objectives include: modeling vulnerabilities from sea level rise and storm hazards, including factors such as water levels, wave heights, flooding, and erosion; using a collaborative product development process to meet stakeholders’ information needs; mapping infrastructure and ecosystem vulnerabilities at scales relevant to planning and management; developing products in accessible, user-friendly formats that can be easily applied to local planning efforts; and providing training and targeted in-depth technical assistance on the use of the decision-support tools.

Final products include: Seamless Digital Elevation Model (DEM) at 2 meter horizontal resolution for the San Francisco Bay Area; suite of sea level rise projections between 0 - 2 meters, with a 5 meter extreme, plus storm scenarios using the Coastal Storm Modeling System (CoSMoS); interactive maps overlaying infrastructure and ecosystem vulnerabilities; online and downloadable data access for use in restoration, adaptation and response planning, tailored to stakeholders’ information needs; and report presenting the project findings and assessing impacts.

How can the OCOF scenario models and flood map help me?

OCOF provides science-based decision-support tools to help understand, visualize, and anticipate local impacts from sea level rise and storms. Examples of planning efforts that could benefit from this information include: determination of infrastructure vulnerability (such as buildings, parking lots, public bathrooms, sewer systems, public transportation stations, rail lines, roads, etc.); determination of community vulnerability; emergency response plans; implications for levee, wetland, shoreline, and infrastructure protection; understanding long-term potential for wetland migration; and prioritization of conservation acquisition and restoration areas.

How is this tool different from other sea level rise mapping efforts?

  1. NOAA Sea-level Rise Viewer: The NOAA Coastal Services Center’s Sea Level Rise and Coastal Flooding Impacts Viewer provides users the ability to visualize areas potentially impacted by sea level rise side-by-side with other data such as critical infrastructure, roads, ecologically sensitive areas, demographics, and economics. This is a sophisticated screening level tool that models coastal flooding from the combination of a high tide and sea level rise only. The data and maps do not include storm surges nor do they account for erosion, subsidence, or future construction. The tool uses a modified bath-tub approach that accounts for local tidal variability using the NOAA VDATUM model and includes hydraulic connectivity.
  2. FEMA California Coastal Analysis and Mapping Project (CCAMP): The CCAMP study area covers the entire California open Pacific coast, including the nine San Francisco Bay Area counties. The new detailed coastal engineering analyses and mapping will revise and update the flood and wave hazard data shown on the coastal Flood Insurance Study reports and Flood Insurance Rate Maps based on existing conditions for each of the twenty coastal counties. Through Risk MAP, CCAMP will develop enhanced products and tools to help communities understand and mitigate existing coastal flood hazards and risks, while OCOF’s online decision support tools project future flood hazards and risks resulting from sea level rise and storms within the San Francisco Bay Area.

What is the difference between the Point Blue Future San Francisco Bay Tidal Marshes website and OCOF?

The Point Blue Future San Francisco Bay Tidal Marshes seeks to understand how tidal marshes and the biota in those marshes are responding to sea level rise. OCOF seeks to understand the extent of flooding expected with sea level rise and various storm scenarios. These are two different approaches to answering a complex set of questions about San Francisco Bay and sea level rise. Scientists from all research organizations are sharing models and best practices for answering these complex questions about the effects of sea level rise on our world.

In general, if you are interested in visualizing flood risks due to storms or higher sea levels, use this OCOF tool. If you are interested in how tidal marshes and tidal marsh birds within San Francisco Bay might respond over time to different sea-level rise and sediment assumption scenarios, take a look at the Future Marshes tool (www.pointblue.org/sfbayslr).

GEOGRAPHIC COVERAGE

What is the current geographic extent and resolution of the Digital Elevation Model and decision support tool?

The resolution is 2 m (a single elevation value is assigned to each 2 x 2 m grid cell) and it extends alongshore of the outer coast from Bodega Head to just south of Pillar Point Harbor in Half Moon Bay. In the cross shore direction it extends from an elevation of +20 meters and offshore to at least the 3 nautical mile limit of state waters. Similarly, the San Francisco Bay digital elevation model is of the same resolution and extends from the Golden Gate all through the south and north bays and to just east of Antioch near the western portion of the Delta. The digital elevation model for San Francisco Bay is available at: http://topotools.cr.usgs.gov/topobathy_viewer/. Near all the land above MHW is based on aerial Lidar flights carried out in summer 2010. Therefore, any changes to the topography post-2010 is not captured by the DEM.

How did you choose the OCOF project boundary?

The boundaries cover all the high-interest sites on the North-central Coast that are vulnerable to present and future coastal storms, including harbors (e.g., Pillar Point, Bodega), popular beaches (e.g., Ocean Beach, Linda Mar), sensitive ecosystems and embayments (e.g., Drakes Estero, Muir Beach, Bolinas Lagoon), and National Park Service Lands (e.g., Point Reyes National Seashore, Golden Gate National Recreation Area).

DATA

Which LIDAR data do you use?

LIDAR data comes from three 2010 surveys: USGS, California State Ocean Protection Council (OPC), and the Golden Gate Lidar Project. See http://pubs.usgs.gov/ds/684/ for the spatial coverage of each survey.

The other primary data for the DEM are depth soundings recently collected using multibeam bathymetry as part of the California Seafloor Mapping Project, a collaborative, multi-institutional campaign (http://seafloor.csumb.edu/csmp/csmp.html).

What are the sources for other data layers shown on the map?

What is the accuracy of the mapping used in this tool?

The DEM and all derived data layers have a horizontal resolution of 2 meters. The elevation data has a vertical accuracy of approximately 18 cm. The horizontal accuracy of the 2010 lidar (the bulk of the topography) has an RMSE of 1m.

How often is the mapping updated with new elevation data?

The DEM utilizes the latest and greatest topography and bathymetry available. There are no current plans to collect new data over this region.

How do I get a copy of the data layers for my own use?

You can download all data layers through the OCOF site. Select Get Data from the main menu to get to the data download utility. You must sign in using your registered email address to access the data utitlity. The data are presented within two tables, one for the outer coast data layers and the other for the inner bay data layers. Locate the sea level rise and storm scenario you want to download and click on the link. You will receive a Zip file with the data in standard formats along with metadata for your reference.

Can I get the digital elevation model (DEM) that was used to create the layers, and how is it different from most other DEMs?

Yes. The DEM is visible in the tool under the "4) Choose other layers" section as Digital Elevation Model (DEM) and available for download at: http://topotools.cr.usgs.gov/topobathy_viewer/. It differs from most other DEMs in that it consists of the most recently available water depth (bathymetry) and land elevation (topography) measurements, merged the data for a seamless topobathy DEM, and has a fine point spacing of 2m.

MODELING - General

What are the components that go into the model results?

The following diagram outlines the components and workflow that drive creating the modeled estimates in this tool:

Which global climate models are used, and why did you choose them?

We use the latest and most sophisticated Global Climate Models from the Coupled Model Intercomparison Project Phase 5 (CMIP5: http://cmip-pcmdi.llnl.gov/cmip5/). These are a set of international climate models with a standard set of boundary conditions designed to collectively simulate the future climate for the 5th assessment report of the Intergovernmental Panel on Climate Change (AR5) , due in 2013. We chose the 4 of the 32 models (BCC-CSM1.1, INM-CM4, MIROC5, and GFDL-ESM2M) that have fine enough temporal resolution (3 hours) to adequately capture the maximum wind speeds so we can model the largest, most realistic waves. The remaining models only output our key parameters from storm modeling, wind and pressure fields, at 6-24 hour intervals, not adequate for resolving the peaks of coastal storms.

Is this based on a “bathtub” modeling approach?

No. Not only are we including both the static (i.e., tides and global sea level rise) and dynamic components of water levels (i.e., surge and wave-driven set-up and run-up), we are also explicitly modeling the flow of the flood waters as well.

Why does the tool show inundation starting at Mean Higher High Water (MHHW)?

Below the Mean Higher High Water are elevations that are wet at some point every day due to expected tidal activity. Elevation alone is not enough to tell you whether you are expected to be flooded due to sea level rise and storm surge activity on top of tides.

Does this tool show timing of inundation levels (e.g., 3 feet by 2100)?

From the OCOF Flood Map, select the Help me with Sea Level Rise projections link. A tool will cover the map that compares expert opinion about when sea level rise estimates will happen. You can ask questions about the range of years when sea level rise scenarios are expected to happen, as well the range of sea level rise scenarios expected for a given year.

The OCOF mapping tool and underlying flood hazard data do not give any time frames directly.

Does the model take into account future changes in geomorphology, shoreline change, etc.?

No, it only models the changes during a single storm. However, the future shoreline position has been projected for 2030, 2050, and 2100 based on the historical rates of change reported in the USGS National Assessment of Shoreline Change for the California coast (http://pubs.usgs.gov/of/2006/1219/).

Are the cumulative impacts from sea level rise and storm surge modeled together?

Yes. Each simulation includes all the relevant components of each storm scenario, including sea level rise, tidal currents, surge (driven by wind and atmospheric pressure), and waves.

How do you model inputs such as rivers and stormwater?

Stormwater is not included in the simulations. Estimates of freshwater inflows from rivers and tributaries are included (the 'Delta', Napa River, Sonoma Creek, Petaluma River, Corte Madera Creek, San Francisquito, Alameda Creek Coyote Creek, and Guadalupe River).

Delta inflow estimates are based on projected discharge rates using a watershed model and precipitation patterns from the GFDL CMIP3 (AR3) model (see http://cascade.wr.usgs.gov/data/Task2-watershed/index.shtm for further explanation and data). Because the CoSMoS model employed atmospheric patterns from the later CMIP5 version of the GFDL model (http://www.gfdl.noaa.gov/cmip) it cannot be assumed that the timing of atmospheric conditions between the two models is the same. Therefore, times when spatial and temporal precipitation patterns over the Delta watershed were similar between the CMIP3 and CMIP5, were identified and used to better approximate Delta discharge rates commensurate with storm patterns in the CMIP5 model.

Discharge rates of the smaller rivers and tributaries (i.e., Napa, Sonoma, etc.) are estimated from quantile (percentage) plots relating historical discharge rates between the Delta and river or creek discharge rates.

What do storm event wave conditions represent in San Francisco Bay

With the exception of central San Francisco Bay where open ocean effects are included, ocean swell waves do not impact much of the interior of the Bay, and wind-driven waves, wind and atmospheric pressure are primary forces for coastal, storm-related flooding. The complex topography of the region greatly affects wind direction and strength, and in turn resulting storm waves, in the different areas of the Bay. Some locations in the Bay receive storm winds from many directions while other areas show storm-related impacts from a smaller range of waves and winds. Individual storm events may also vary in wind direction, strength, and pressure affecting sections of coastline, susceptible to particular directions of waves, currents and water levels, differently. Therefore, in order to capture the full extent of flooding possible with major storm events (20-year and 100-year storm events in 21st century climate models), storm scenarios for predominant wave and wind directions in the Bay’s primary sub-regions are modeled (Suisun Bay, San Pablo Bay, Central Bay, and South Bay; see figure). The resultant flood projections are a combination of the maximum flooding for all predominant storm directions in each sub-region.

Annual storm (i.e., 1-year) scenarios are modeled from a single, 21st century storm event and do not include multiple storm directions as directional differences are not as significant throughout the Bay.

What does the term "wave runup" refer to?

Wave runup is the maximum vertical extent of wave uprush on a beach or structure above the still water level

MODELING - Scenarios

What is storm scenario frequency and what do 0-year (i.e., no storm), 1-year, 20-year, 100-year storm event wave conditions represent?

Simply stated, a storm scenario frequency is an estimate of how long it will be between storms of a given magnitude. For example, the 20-year storm event is expected to occur once in 20 years. Equivalently, one can say that there is a 5% chance that a storm of that magnitude will occur in any one year.

It is important to remember that this is based on statistics - there is no guarantee that once such a storm has hit the coast it will not happen again for another 20 years. If you had measurements of wave heights covering 100 years, there would be five such storms in that data series (an average of once every 20 years). These storms could occur in consecutive years or several in a single year.

The 0-, 1-, 20-, and 100-year storm events used in this work for the outer coast were derived from numerically modeled wave heights using projected winds for the 21st century. Statistical analysis of the wave height record offshore of San Francisco indicates that the median wave height in deep water (0-year storm, i.e., average daily conditions) will be on the order of 2.4 m while offshore wave heights associated with a 100-year storm will exceed 9.8 m.

Similar to the outer coast study, the 0-, 1-, 20-, and 100-year storm events used for San Francisco Bay were derived from numerically modeled wave heights using projected winds for the 21st century. However, storm identification for the Bay differed from the outer coast in three important ways: (1) in-Bay wave heights (as opposed to offshore wave heights) were computed, and only using the GFDL climate model (for the outer coast, winds from a total of four climate models were used (GFDL, INMCM, BCC, and MIROC5); (2) maximum wave heights oriented perpendicular to the major orientations of the shoreline within each basin (south, central, north and Suisun) were used to identify storm events; and (3) in addition to wave heights, estimates of elevated water levels from passing low pressure systems and longer term sea level anomalies related to, for example, El Niño were used to derive a proxy of total water levels. The 0-, 1-, 20-, and 100- year events were then identified from statistical analyses of the proximal total water level in each basin. These selected storm events were then modeled in detail with the full time-series of spatially and temporally varying winds, pressure fields, tides, offshore wave conditions, and freshwater inputs. It should be noted that no extreme events were identified in some basins and incident wave directions (e.g., northeasterly winds/waves in Suisun Bay),

What is the king tide scenario?

The king tide scenario depicts flooding extents expected inside San Francisco Bay with an extreme high tide, or king tide, and it was modeled using water level conditions from the 30 January 2014 king tide event. The flood projections are determined from a basic model accounting for tidal forcing only, and do not include atmospheric pressure, wind, waves, or other conditions included in average or storm wave scenarios.

These scenarios were modeled only for inside San Francisco Bay and are not available for the outer coastline.

What does flood duration show in San Francisco Bay?

Flood duration values represent the time an area is covered by flood waters for a given scenario during one spring tide cycle (24.84hrs). Spring tides are as much as 55 cm higher than neap tides and persist for about 2 weeks every month. Durations were calculated from a coarser grid than used for flooding, and thus fine-scale features (such as dikes and shore-armoring) may not be fully represented. As a consequence, duration times illustrate the estimated inundation time for a general area (~100 × 100 meters wide). Calculated duration data are not available some low-lying marsh regions (for example, small areas within Suisun Bay) where LiDAR offsets due to dense vegetation were particularly significant.

MODELING - Flood Extents

What goes into flooding potential in San Francisco Bay? Why does the Minimum Inundation layer sometimes appear similar to projected flooding extents?

Variations in the DEM, projected changes in marsh elevation, offsets in LiDAR data, and normal ranges in calculated flood projections can all result in changes to the modeled flood extent. Including these ranges of inputs, or uncertainty (figure left), yields an estimate of the potential minimum or maximum flood extent. Several processes and inputs were accounted for as components in San Francisco Bay’s total uncertainty: overall accuracy of the DEM, average elevation offsets due to vegetation in 12 marsh areas, inherent variation in model calculations, projected marsh elevation changes, and vertical land motion. As most of these components varied by location and SLR, such as vertical land motion (figure right), total uncertainty is not uniform throughout the Bay (figure left).

The model used to compute flooding extent has a slightly larger resolution than the DEM on which its results are projected. Due to this difference, minimum flood potential closely resembles currently projected flood extents.

For more information on components used in uncertainty, see our References page for work by Shirzaie, et al., Takekawa, et al., and Veloz, et al.

A manuscript in preparation will have additional information regarding methods for illustrating uncertainty in flood projection. Contact Patrick Barnard for more information.

Why doesn't the flood extent reach the wet-dry line on the background image for the 0cm Sea Level Rise (SLR) with average wave conditions (0-year/no storm) in my study area?

Projected flood extents are intended to represent the maximum landward extent where standing water is expected for the duration of several minutes or more. This is usually below the maximum wave run-up line, where intermittent wave uprush is expected to reach and recurrent wetting and drying occurs.

Beach profiles change frequently, both seasonally and from year to year. Although the digital elevation model (DEM) used in this study has the latest comprehensive data available, it does not capture any recent changes in beach profiles or necessarily coincide with profiles indicated in aerial imagery. Changes in beach profile can yield variations in flooding extent and maximum wave run-up that might be especially noticeable in relation to the visible wet/dry lines on beaches in the imagery. When viewing SLR 000 cm results, flood extents affected by such beach profile changes are observable in the DEM and in relation to the visible wet/dry line in many locations, particularly on sand spits such as at the mouth of Bodega Bay, Tomales Bay, Drakes Estero, entrance to Valley Ford, Bolinas, entrance to Rodeo Lagoon, and open beaches along Point Reyes Beach, Muir Beach, northern Pacifica, Pillar Point and Half Moon Bay State Beach.

Why does the flood extent for certain low SLR/storm scenarios sometimes seem to flood more than a higher SLR/storm scenario in my study area?

In certain locations, flooding does not progress in a consecutive manner with regard to SLR or storm event. There are two main reasons why this occurs:

  • Direction of incoming waves: The first is due to changes in wave height as they approach the shore from different angles. Within the CoSMoS structure, each storm event generated waves of different heights and directions offshore central California (see above for more information). 100-year event waves approached from a northwest direction, while 20-year event waves approached from the west. As waves approach the shore, bathymetric variability along the coast causes waves to change direction and approach different locations at different angles resulting in focusing or de-focusing of wave energy relative to other locations. Additionally, as waves change direction to approach the shore nearly straight on, some energy is lost in the form of decreasing wave height. Differences in wave approach angles for particular locations can result, for example, in flooding extent from the 20-year storm event, when waves may approach an area of coast more directly, exceeding 100-year storm event extents, when the generated waves may be larger but approach from a more oblique angle (see Figure right). This is particularly noticeable along south and southwest-facing coastlines such as Drakes Estero, Stinson Beach, Muir Beach, Horseshoe Cove, Rodeo Lagoon, and Pillar Point.

  • Eroding shoreline: The other reason that non-consecutive flooding occurs and small SLR/storm scenarios may have flooding extents greater than larger SLR/storm scenarios in limited areas is because of the complex nature of beach profile erosion simulated within the models. For each storm event, the same starting beach profile was used for a specific location along the coast. This profile was allowed to erode for the given storm within the model structure. Because of differences in wave height, length, and angle of wave approach, the erosion and deposition along the profile evolved in a non-progressive* fashion and subtle changes caused differences in the calculated extent of standing floodwater and maximum run-up. Most of this behavior is notable during stronger storm events (20-year and 100-year events) when there is considerable shoreline change.

Why do flooding extents in some areas of San Francisco Bay look “scalloped”?

(see eastern South Bay near Hayward, Suisun Bay, ponds S/SW of Napa)

The curved, or “scalloped” (see figure), flood edge in some areas is a by-product of the method used to extract flood level data from the model and then project it on the DEM. Overall flooding extents and flood depth values are not affected. This artifact is most noticeable in lower-SLR scenarios and in low-elevation areas including portions of South Bay, small areas of Richmond, Suisun Bay, and marshes and ponds south of Napa.

Why does the flooded region for certain storm scenarios occasionally seem more extensive than a stronger storm scenario in my San Francisco Bay study area?

(see ponds and marshes N of San Pablo Bay, Suisun Bay, South Bay ponds N/NE of Moffett Field)

In certain locations inside San Francisco Bay, flooding does not progress in a sequential manner with respect to storm event. This effect is more common in areas with multiple pond structures or networks of levees. A primary reason may be direction of the storm event with regard to clustered levees and ponds. Individual levees, dikes, armoring, and portions thereof, can be susceptible to particular directions of storm currents, waves, or increased water levels. While predominant storm directions were modeled for different regions of the Bay, subtle differences in direction may result in associated flood waters circumventing particular sections of levees or armoring, allowing flooding into the interior. As the levees/dikes on the remaining borders may not be as robust as the primary structure encountered, flooding may migrate into neighboring ponds leading to larger sections ponds and marsh behind armoring to be flooded. Additionally, any recent or undocumented changes in structure to levees and dikes may not be accounted for in the model and can affect flood infiltration to these areas.

MODELING - Marshes and Wetlands

Why don't marshes appear flooded under the selected scenario?

In some cases, the LiDAR may not be penetrating the tall dense marsh vegetation and the resulting elevation is biased high, reflecting the height of the vegetation as opposed to bare earth. In this case, some marsh vegetation may still be exposed under the chosen scenario and thus the marsh does not appear to flood.

Another cause for marshes not appearing to flood could be due to the complexities of modeling water movement through networks of tidal sloughs and channels especially in areas where local tide gauge information is lacking or erroneous.

To better understand tidal marsh response to sea-level rise over time under different scenarios, please also visit the Point Blue Future San Francisco Bay Tidal Marshes tool (www.pointblue.org/sfbayslr).

Why do flood extents for particular marshes seem low?

(see ponds and marshes N of San Pablo Bay, upper Napa, Suisun Bay, China Camp, Corte Madera, marshes of east Palo Alto, marsh areas west of Hayward)

The DEM in this study primarily originates from LiDAR data collected in 2010. Recent work in a dozen, isolated locations throughout San Francisco Bay show that LiDAR was unable to penetrate thick vegetation, and resultant elevations are often higher than actual ground surfaces in these locations (http://pubs.usgs.gov/of/2013/1081/). On average across all 12 sites, LiDAR-derived DEM elevations within these marshes are offset 20 cm too high. Each study site showed variation within its respective marsh, with offsets ranging from -10 cm (DEM lower than measurements) to 29 cm (DEM higher than measurements), but site data also shows localized and inconsistent patterns, as the ability of LiDAR to penetrate vegetation is dependent on vegetation type, density, and season. To account for these elevation differences, a site-averaged offset was included in the estimates of maximum flooding potential at these survey locations. Without additional work to document comprehensive marsh vegetation variation and resultant offsets, credible modifications to DEM elevations could not be made throughout the Bay.

As a consequence of this vegetation elevation offset, modeled flood levels in densely vegetated areas are likely too low and flood extents under-predicted. This is observable in several areas throughout the Bay, but most notably in marsh areas neighboring San Pablo Bay and surrounding ares. In these locations, the maximum flood potential is a more suitable illustration of probable flooding extent. Coincident flood depths and durations of these areas should be understood as under-predicted.

To demonstrate what type of influence this vegetation offset can have on flood extent, a separate study was conducted for the National Estuarine Research Reserve at China Camp. The measured vegetation offset at this location was accounted for with detailed modifications within the modeling framework. With the correction applied, flood extents expanded landward over 300 meters at some locations (see figure).

For more information on marsh elevations, see our References page for work by Takekawa, et al.

MODELING - Levees, Piers and Hardened Structures

Does the model take into account levees and/or hydraulic features, such as culverts, pipes, and bridges?

The model accounts for levees and structured mounds visible in the 2010 DEM but NOT any culverts, pipes, piers, pilings, or bridges. If you want to see if a particular feature was included, go to the OCOF Flood Map and turn on the Digital Elevation Model. Zoom into the feature of interest and see if you can discern them, or download the area of interest with the upper right most button on the map and examine the data in a GIS package.

The model does not account for any culverts, pipes, pilings, or bridges.

How are levees and dikes accounted for in the Bay? Why are some ponds depicted as flooded while others aren’t?

(see South Bay ponds N/NE of Moffett Field, Suisun Bay, San Pablo Bay ponds N of Hwy 37, San Rafael, Foster City/Redwood City, Richmond, Santa Venetia, SFO, and OAK)

In the Bay area, projected flooding extents show landward locations from the Bay where standing water is expected for several minutes or more, and in locations with existing standing water (such as ponds or behind levees) where a change in water level is predicted (i.e., flood waters entering an area through a hydrologic connection, overtopping or by other means).

Modeling flood behavior in the vicinity of levees and dikes requires good spatial knowledge of the structure and high modeling resolution in the location, as some structures are only a handful of meters wide. The high resolution Digital Elevation Model (DEM) used in this study contains the most recent and complete elevation data available, including topographic LiDAR collected in 2010, covering most areas above MHW. Therefore most natural or artificial modifications to the topography since 2010 are not captured. Alterations were made to the underlying modeling structure in numerous locations (including Foster City, Redwood City, Coyote Creek, Alviso, San Francisco International Airport, Oakland International Airport, Richmond, Corte Madera, San Rafael, in vicinity Novato, and Suisun Bay among other locations; figure 2) to ensure the current spatial extent and physical function of levees and dikes were modeled properly. Additionally, known breaches and openings were similarly accounted for. No assumptions on levee strength, durability, or possible alterations were made or modeled. Recent or undocumented changes to include reinforcements and breaches may not be captured, leading to possible flooding where recent protections have been added or vice versa.

Does the model take into account land use changes on the shoreline, and the addition of infrastructure like seawalls?

Yes, indirectly. Coastal slopes greater than 30 degrees are assumed to be hard structures, such as jetties and seawalls, and are assumed to not erode over the time scale of the storms being simulated.

Why are some piers shown as flooded and some not?

(see Embarcadero, Richardson Bay, Hunters Point)

Flooding extents show locations where the elevation of modeled flood waters is higher than the DEM. The DEM is a depiction of the bare earth surface elevation, or ground, on which the flood waters flow and does not include the elevation of buildings or similar transient structures. While breakwaters and similar earthen works are included in the DEM, many piers and docks on pilings (especially those smaller than ~75 meters in width) are not included, and the body of water flowing beneath the structure is modeled (figure 4, left and center illustrations).

Projected flooding depths are shown for flooded locations above the current shoreline, delineated by SFEI’s Bay Area Aquatic Resource Inventory (BAARI) shoreline. This shoreline contains many of the same large piers included in the DEM, but inclusion of some mid-sized structures differs. This inconsistency results in apparent deep flood depths over the pier involved (figure 4, center and right illustrations), and the flood extent and depth actually show the uninterrupted total water depth beneath the structure. Occasionally, flood depths may be visible along the perimeter of some large piers. This is strictly an artifact of the difference in resolution between the flood model (~10 m in high-resolution sites) and the DEM, and is not a true illustration of flooding.

For larger pier structures included in the DEM, depicted flood extents and depths over the full structure represent legitimate overtopping. The behavior of flooding at a pier’s surrounding shoreline can aid in identifying projected flooding of the location: if there is inundation of the adjacent coastal area that is consistent with a pier, then it is expected that flooding of the pier is genuine.

DECISION SUPPORT TOOL

Is the resolution high enough to visualize impacts to a single parcel or building?

The DEM resolution of 2 m was selected to enable the possibility of asking questions at a parcel scale. We suggest you examine all modeled data layers and understand the assumptions that are behind these models when using these data.

Can I add my own layers with data specific to my project or site?

No. We have made the data used in the tool available for downloading from the OCOF mapping tool in standard GIS formats.

What types of maps or other products can be exported?

We have developed a standardized pdf report which summarizes model results for a user defined area. The report will include summaries and graphs of area you select interactively and a copy of the map.

We also have a tool on the map that lets you draw a rectangle and get a package of data layers.

Can I build mashups with the tool?

The OCOF mapping tool is built with open source technologies with map data delivered through Open Geospatial Consortium standards (http://www.opengeospatial.org/). If you are interested in mashing up portions of OCOF, please contact Michael Fitzgibbon at Point Blue Conservation Science (mfitzgibbon@pointblue.org).

Is there a mobile app to access this information in the field?

You can access the OCOF web site on a tablet computer with internet access. We are looking at the possibilities of mobile applications in the future.

Can I get the tool source code?

Yes. Please contact Michael Fitzgibbon at Point Blue Conservation Science (mfitzgibbon@pointblue.org).

USER FEEDBACK

How do I provide feedback on this tool?

Look for the “Feedback” link on each page for sending the team your thoughts, issues and ideas about the research, website and interactive tools. We would love to hear from you!

MISCELLANEOUS

Will there be an endorsement by the State of California that this is approved for CEQA analysis?

It is unlikely that the State of California will endorse any specific tool for sea level rise analysis within CEQA. State policies and guidance regarding climate change considerations are constantly evolving, so you should contact the appropriate agency for more information.

FUTURE DEVELOPMENT OF OCOF

Coastal planning is an evolving science and the models will continue to develop. Will there be new versions of these model results in the future?

There are no definitive plans to update the model system and presented results. It is important to note that all models are simplifications of the physics that that cause changes in the natural environment and can only provide approximations to the currents, shoreline erosion, and flooding extents presented in this work. Although different results might be attained with different models and a different approach to the overall strategy, the models and framework used in this work are considered to be state-of-the-art at this time.


*The term, non-progressive flooding, refers to results where more intense storm events (or higher sea-level rise scenarios) do not produce more flooding than less extreme storm conditions (or sea-level rise scenarios).

Updated: August 13, 2014

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