CCAP Landcover Atlas

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CCAP Landcover Atlas creates map visualizations of C-CAP coastal land cover data and land cover change. Also provided: land cover trends for multiple dates; specific land cover changes associated with development, forestry, and wetlands; and the tables, maps, and summary reports used to enhance communication and decision-making.

General
Developed
Forests
Wetlands

General

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General

Land cover changes

What is land cover?

Land cover data document the types of features that cover the surface of the Earth. These data quantify how much of a region is covered by forests, wetlands, impervious surfaces, and agriculture―as well as these feature’s locations.

It may be important to differentiate land cover from land use, which documents how those cover types are being used (residential, commercial, recreational). The same cover type can be managed or used very differently. A forest land use, for instance, may include land covers other than trees. But when we map forested land covers, we mean trees.

Why are changes to the surface area of the landscape relevant?

It is difficult to manage any area or land resource without having an accurate picture of existing conditions. Land cover data can help provide that big-picture view. It is also beneficial to understand how these resources have changed. Comparing land resource data from one year to the next can be used to evaluate how a community’s past land management efforts are working and can provide valuable information on trends to aid future planning initiatives. Hopefully, this information will provide better context for management decisions.

How are C-CAP change maps produced?

C-CAP products are developed using multiple dates of remotely sensed imagery. Change detection analysis compares the two dates of imagery to identify the areas that have likely changed during this time frame. These areas are then classified through a combination of models, use of ancillary data, and manual edits.

Developed

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Developed

Developed Gains Developed Loss

What is an impervious surface?

An impervious surface is composed of any man-made material that impedes or prevents the natural infiltration of water into the soil mantle. Such surfaces include building roofs, patios, sidewalks, concrete or asphalt streets, parking lots, and gravel roads. This definition does not include rock outcroppings or compacted earthen materials that could also increase or divert water flow, thus preventing infiltration.

Why is the impervious surface area of the landscape relevant?

When impervious surfaces cover areas where water naturally seeps into underground water sources, or aquifers, they reduce the amount of water available to recharge wells and springs. During storms, excess water that could not seep into the ground flows across impervious surfaces where it can gather harmful pollutants (e.g., oil and fertilizer) and deposit them into surrounding waters and farther downstream. As impervious surfaces increase, so do stormwater runoff volumes, the velocity of stormwater flows, and pollutant levels in runoff (Schueler, 1994).

How is impervious different than development?

Developed features are made up of impervious surfaces, but also include the grasses (and potentially smaller amounts of other cover types, such as individual trees in yards) that surround these man-made impervious features.

What developed classes are mapped in the Land Cover Atlas?

In the Regional land cover data, produced for the Contiguous United States (CONUS), we map 4 categories of developed features. These include:

Developed, High Intensity - Each pixel comprises 80 to 100 percent concrete, asphalt, or other constructed materials. Vegetation, if present, occupies less than 20 percent of the landscape. This class includes heavily built-up urban centers and large constructed surfaces in suburban and rural areas with a variety of land uses.
Developed, Medium Intensity - Each pixel comprises a mixture of constructed materials and vegetation or other land cover. Constructed materials account for 50 to 79 percent of total area. This class commonly includes multi- and single-family housing areas, especially in suburban neighborhoods, but may include all types of land use.
Developed, Low Intensity - Each pixel comprises a mixture of constructed materials and substantial amounts of vegetation or other land cover. Constructed materials account for 21 to 49 percent of total area. This class commonly includes single-family housing areas, especially in rural neighborhoods, but may include all types of land use.
Developed, Open Space - Each pixel comprises a mixture of some constructed materials, but mostly managed grasses or low-lying vegetation planted in developed areas for recreation, erosion control, or aesthetic purposes. Constructed surfaces account for less than 20 percent of total land cover.
In the High Resolution land cover, produced for the Pacific and Caribbean Islands, we map two categories of developed features. The various intensities of development are no longer applicable, as areas are mapped with a significantly higher level of spatial detail where features or either impervious or not. These categories include:
Impervious - Anthropogenic features such as buildings, parking lots and roads developed from asphalt, concrete or other constructed surfaces which do not allow infiltration from precipitation.
Developed, Open Space - Each pixel comprises a mixture of some constructed materials, but mostly managed grasses or low-lying vegetation planted in developed areas for recreation, erosion control, or aesthetic purposes. Constructed surfaces account for less than 20 percent of total land cover.

How is a pixel's percentage of imperviousness calculated?

In the Regional land cover data (CONUS area) Coefficients were derived for each of the four Coastal Change Analysis Program (C-CAP) developed categories. These values were based on National Land Cover Database (NLCD) 2001 Imperviousness data (Coan et al., 2003).These coefficients represent the average impervious values for each category nationwide. For developed, high intensity, it is 0.8503;for developed, medium intensity, it is 0.5768; for developed, low intensity, it is 0.2929; and for developed, open space, it is 0.0941.

In the High Resolution land cover data (island geographies) no coefficients were necessary. The area of the impervious class was simply summed and divided by the total area of the appropriate watershed and/or county.

How are development "gains" and "losses" defined in the Land Cover Atlas?

With respect to the Land Cover Atlas, a development "gain" occurs when either of the following criteria is met: (1) a pixel changed from a non-developed class in the early date to a developed class in the late date, or (2) a pixel that was mapped as a developed class in the early date changed to a greater intensity of development in the late date (e.g., developed, low intensity to developed, high intensity). Conversely, a development "loss" occurs when either of the following criteria is met: (1) a pixel changed from a developed class in the early date to a non-developed class in the late date, or (2) a pixel that was mapped as a developed class in the early date changed to a lower intensity of development in the late date.

References

Schueler, T. R., 1994. The importance of imperviousness. Watershed Protection Techniques, 1(3): 100-111.

Coan, M. J., B. K. Wylie, C. G. Homer, C. Huang, and L. Yang, 2003. An approach for mapping large-area impervious surfaces: synergistic use of Landsat-7 ETM+ and high spatial resolution imagery. Canadian Journal of Remote Sensing, 29(2): 230-240.

Forests

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Forested

Forest Gains Forest Loss

What do we mean by forest?

Forest is a term used to denote the presence of trees on the landscape, and reflects the ground cover at that location, not necessarily the land use. For instance, while an area might be considered a forest, in terms of its use, it can possess a range of land covers in addition to trees (grass, shrub height vegetation, bare ground, etc). Within C-CAP data, only the portion of these areas that are mapped as tree would meet the definition of a forest cover type. In addition, tree cover in areas outside of such designated forests would also be considered “forest.” In higher resolution land cover products (as seen in Hawaii and the US Territories), this can include small groupings, or even individual, trees (but we keep the forest name for classification consistency).

Why is the forest area of the landscape relevant?

Forest cover provides interception, absorption, and natural pollutant processing for rainfall and surface water. Urban trees serve as an inexpensive storm water practice, lowering water treatment costs. In areas with lower levels of development, forest cover is often the best indicator of watershed health. In addition, change related to forest cover (cuts and regrowth) can account for a large percentage of all changes in many areas. As such, it is important to have an understanding of these trends.

What forest classes are mapped in the Land Cover Atlas?

We map up to five types of forested features. These include:

Deciduous Forest – Contains areas dominated by upland trees generally greater than 5 meters tall and greater than 20 percent of total vegetation cover. More than 75 percent of the tree species shed foliage simultaneously in response to seasonal change.
Evergreen Forest – Contains areas dominated by upland trees generally greater than 5 meters tall and greater than 20 percent of total vegetation cover. More than 75 percent of the tree species maintain their leaves all year. Canopy is never, or rarely, without green foliage.
Mixed Forest – Contains areas dominated by upland trees generally greater than 5 meters tall and greater than 20 percent of total vegetation cover. Neither deciduous nor evergreen species are greater more than 75 percent of total tree cover. Both coniferous and broad-leaved evergreens are included in this category.
Palustrine Forested Wetland – Includes tidal and nontidal wetlands dominated by woody vegetation greater than 5 meters in height, and all such wetlands that occur in tidal areas in which salinity due to ocean-derived salts is below 0.5 percent. Total vegetation coverage is greater than 20 percent.
Estuarine Forested Wetland – Includes tidal wetlands dominated by woody vegetation greater than 5 meters in height, and all such wetlands that occur in tidal areas in which salinity due to ocean-derived salts is greater than 0.5 percent. Total vegetation coverage is greater than 20 percent.

How are forest “gains” and “losses” defined in the Land Cover Atlas?

With respect to the Land Cover Atlas, a forest "gain" refers to pixels that changed from a developed (i.e., high intensity, medium intensity, low intensity, and open space), agricultural (i.e., cultivated crops and pasture/hay), shrub-scrub (both upland and wetlands), grassland, emergent wetland, barren-land, or open-water class in the early date to a forested class in the late date. This can include changes to both palustrine and estuarine forested wetland types. Conversely, a forest "loss" refers to pixels that changed from a forest class (including forested wetland types) in the early date to a developed, agricultural, shrub-scrub (both upland and wetlands), grassland, emergent wetland, barren land, or open water class in the late date.

Wetlands

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Wetlands

Wetland Gains Wetland Loss

What are wetlands?

The U.S. Environmental Protection Agency (EPA) defines wetlands as lands that are inundated or saturated by surface or ground water at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation (i.e., hydrophytes) typically adapted for life in saturated soil conditions (i.e., hydric soils). Wetlands generally include swamps, marshes, bogs, and similar areas (EPA, 2010).

Why are wetlands relevant?

Wetlands help protect our natural ecosystems by providing a wide range of hydrological and ecological benefits, including flood protection and erosion control (i.e., green infrastructure), filtration of toxins and nutrients from runoff, recharge and discharge of groundwater resources, and vital habitat for a multitude of plant and wildlife species. Additionally, wetlands are important natural resources for recreation and education and provide economic commodities such as fish, rice, timber, and peat.

What wetlands classes are mapped in the Land Cover Atlas?

Palustrine Forested Wetland - Pixels include tidal and non-tidal wetlands dominated by woody vegetation greater than or equal to five meters in height, as well as all such wetlands that occur in tidal areas in which salinity due to ocean-derived salts is below 0.5 percent. Total vegetation coverage is greater than 20 percent.
Palustrine Scrub/Shrub Wetland - Pixels include tidal and non-tidal wetlands dominated by woody vegetation less than five meters in height, and all such wetlands that occur in tidal areas in which salinity due to ocean-derived salts is below 0.5 percent. Total vegetation coverage is greater than 20 percent.
Palustrine Emergent Wetland - Pixels include tidal and non-tidal wetlands dominated by persistent emergent vascular plants, emergent mosses, or lichens, and all such wetlands that occur in tidal areas in which salinity due to ocean-derived salts is below 0.5 percent. Total vegetation cover is greater than 80 percent.
Estuarine Forested Wetland - Pixels include tidal wetlands dominated by woody vegetation greater than or equal to five meters in height, and all such wetlands that occur in tidal areas in which salinity due to ocean-derived salts is equal to or greater than 0.5 percent. Total vegetation coverage is greater than 20 percent.
Estuarine Scrub/Shrub Wetland - Pixels include tidal wetlands dominated by woody vegetation less than five meters in height, and all such wetlands that occur in tidal areas in which salinity due to ocean-derived salts is equal to or greater than 0.5 percent. Total vegetation coverage is greater than 20 percent.
Estuarine Emergent Wetland - Pixels include all tidal wetlands dominated by erect, rooted, herbaceous hydrophytes (excluding mosses and lichens). This classification includes all such wetlands that occur in tidal areas in which salinity due to ocean-derived salts is equal to or greater than 0.5 percent and that are present for the majority of the growing season in most years. Total vegetation cover is greater than 80 percent.
Unconsolidated Shore - Pixels include material (such as silt, sand, or gravel) that is subject to inundation and redistribution due to the action of water. Substrates lack vegetation except for pioneering plants that become established during brief periods when growing conditions are favorable.

How are wetland "gains" and "losses" defined in the Land Cover Atlas?

With respect to the Land Cover Atlas, a wetland "gain" refers to pixels that changed from a developed (i.e., high intensity, medium intensity, low intensity, and open space), agricultural (i.e., cultivated crops and pasture/hay), barren-land, or open-water class in the early date to a wetland class in the late date. Conversely, a wetland "loss" refers to pixels that changed from a wetland class in the early date to a developed, agricultural, barren land, or open water class in the late date.

NOTE: The mapped data does not capture changes between wetland types, as such changes do not represent a true "gain" or "loss" of wetlands, but instead a transition from one wetland type to another (e.g., forested wetland that is harvested and becomes emergent wetland, or re-grows to scrub/shrub or mature forest). Such changes are however, included in the numerical data reported on the sidebar of the application.

References

EPA, 2010. Protection of Environment. 40 C.F.R. pt. 232.2.

General

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Developed

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Forests

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Wetlands

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Website Owner: Office for Coastal Management - Last Modified