Corte Madera Shoreline Flood Explorer

An adjustment in natural or human systems to a new or changing environment. Adaptation to climate change includes proactive planning and preparation to reduce risk, utilize new opportunities and enhance resilience.

Changes in average weather conditions that persist over multiple decades or longer. Climate change encompasses both increases and decreases in temperature, as well as shifts in precipitation, changing risk of certain types of severe weather events, and changes to other features of the climate system.

The Coastal Storm Modeling System (CoSMoS) is a modeling approach developed by the U.S. Geological Survey that projects coastal flooding and shoreline change (sandy beach change and cliff retreat) due to both sea level rise and coastal storms driven by climate change. CoSMoS was designed to understand the present-day and future vulnerability of the coast in support of federal and state climate change guidance, local planning, and emergency response. Learn more and view the CoSMoS tool on the Our Coast, Our Future website.

Datum: A base elevation used as a reference from which to measure heights or depths. Learn more about datums on NOAA’s Tides & Currents website.

Tidal datum:  A tidal datum is a standard elevation defined by a certain phase of the tide. Tidal datums are used as references to measure local water levels and should not be extended into areas having differing oceanographic characteristics without substantiating measurements.

Geodetic datum: The National Geodetic Survey (NGS) defines a geodetic datum as: "A set of constants used for calculating the coordinates of points on the Earth." In surveying and geodesy, a datum is a reference point on the earth's surface against which position measurements are made, and an associated model of the shape of the earth for computing positions. Horizontal datums are used for describing a point on the earth's surface, in latitude and longitude. Vertical datums are used to measure elevations or underwater depths.

The Federal Emergency Management Agency. FEMA maintains maps of flood zones, provides flood insurance and resources to reduce flood risk, and offers financial support via grants to local governments.

Flood barrier: A flood defense system that adds elevation to prevent water from passing through and getting into yards, streets, homes, and businesses. Some examples of specific types of flood barriers that add elevation are levees, seawalls, and ecotone slopes

Levee: An embankment built for flood protection. They are usually earthen embankments and have water only on one side. Levees protect land that is normally dry but may be flooded during extreme events. Staff uses this term to refer to engineered, FEMA-accredited barriers, as opposed to flood berms. (Source)

Flood berm: Typically an earthen structure, constructed from local compacted fill, that protects land from flooding. Staff uses this term to refer to earthen barriers such as the Marina Village Flood Berm, which is not FEMA-accredited. (Source)

Seawall: A structure made of concrete, masonry or sheet piles. It is built parallel to the shore at the transition between the beach and the mainland or dune, to protect the inland area against wave action and prevent coastal erosion. (Source)

Ecotone slope: Ecotone slopes are ramps (with a length to height ratio of 10:1 or gentler) bayward of flood risk management levees and landward of a tidal marsh. They can provide wetland-upland transition zone habitat when properly vegetated with native clonal grasses, rushes, and sedges. Ecotone slopes can attenuate waves before they reach the levee, provide high-tide refuge for marsh wildlife, and allow room for marshes to migrate upslope with sea level rise.

The National Oceanic and Atmospheric Administration. NOAA's Center for Operational Oceanographic Products and Services (CO-OPS) is the authoritative source for accurate, reliable, and timely tides, water levels, currents, and other coastal oceanographic and meteorological information. 

The North American Vertical Datum of 1988, a geodetic vertical datum that serves as a standard reference point for measuring elevations or depths. 

Increase in the mean level of the ocean. Relative sea level rise occurs where there is a net increase in the level of the ocean relative to local land and is a combination of thermal expansion of ocean water, increases in water volume due to the melting of land based ice, and vertical land movement or subsidence. 

The State provides sea level rise science and guidance in their report, State of California Sea Level Rise Guidance: 2024 Science and Policy Update. Several sea level rise viewers are available to help visualize where sea level rise impacts may be experienced:

Our Coast, Our Future Hazard Map

BCDC Bay Shoreline Flood Explorer

NOAA Sea Level Rise Viewer

A gradual settling or sinking of the Earth’s surface. The bayside neighborhoods of Mariner Cove and Marina Village were built on filled baylands in the 1950’s. The neighborhoods have subsided as the bay mud and former marsh solids consolidate under the weight of the overlying infrastructure (e.g., earth fill, roads, homes). (Source)

A rise or piling up of water generated by high winds and low atmospheric pressure in the presence of a storm that is over and above the predicted astronomical tide. The magnitude of a storm surge and the height of an astronomical tide are additive: when the sum of the two is unusually large, an extreme storm event occurs.

Precipitation that runs off the landscape. When rain hits saturated or impervious ground, it begins to flow overland downhill. Rainfall intensity, amount, and duration all impact runoff. (Source)

The Town maintains a large network of infrastructure to manage stormwater and recently completed a draft 2024 Storm Drain Master Plan which provides an analysis of the existing storm drain system capacity and includes recommendations on future infrastructure projects to maintain and improve the storm drain system.

Tides are very long-period waves that move through the ocean in response to the forces exerted by the moon and sun. Tides originate in the ocean and progress toward the coastlines where they appear as the regular rise and fall of the sea surface. When the highest part, or crest, of the wave reaches a particular location, high tide occurs; low tide corresponds to the lowest part of the wave, or its trough. The difference in height between the high tide and the low tide is called the tidal range. (Source)

NOAA provides tide predictions and observations on their website. Staff typically reference the Richmond station when looking up tidal information as it is the closest station within the San Francisco Bay.

King tide: An especially high tide caused by alignment of gravitational pull between the sun and the moon. King Tides are the highest high tides of the year, about a foot or two higher than average tides, occur naturally and regularly (about 5-6 times each year), and are predictable and expected. When King Tides occur during floods or storms, water levels can rise higher and have the potential to cause great damage to the coastline and coastal property.