1) Develop methods that can be easily replicated for other areas of the Pacific Northwest;
2) And, attempt to exceed the accuracy and efficiency of conducting a similar study based on aerial photointerpretation, which is often costly and time-consuming.
Land cover is the observed (bio)physical cover on the Earth's surface, while land use is the use is what the land is used for by humans (e.g. protected areas, timber land, etc.). While land cover allows us to see overall biophysical cover, land use allows us to see patterns of development, management practices, and more.
Due to the temporal range of the data land cover classifications were not tested or verified. Training datasets for the land cover classifications were developed from the original Landsat imagery by visual inspection. Overlapping classified Landsat scenes were used to calcualte a correlation metric for each time period. Agreement between land cover classes can be seen in the table below.
1988 1996 2004 Built-up 93% 92% 96% (+/- 7.42) (+/- 5.50) (+/- 2.25) Coarse 90% 87% 89% (+/- 3.16) (+/- 9.60) (+/- 4.86)
In addition to the Landsat imagery, two datasets were used in eCognition to assist in object segmentation and classification. Delineated floodplains and elevation bands were used to differentiate between irrigated agricultural lands and light forest cover, regeneration harvests and bare agricultural soils. Two segmentation levels were used to differentiate between large areas of relatively homogeneous land cover and small areas of development. This resulted in two different land cover classifications: a general land cover classification (i.e. forest or irrigated lands) and a developed (i.e. concrete, rooftops) land cover classification.
1. Dark Forest: Mature evergreen forest cover 2. Light Forest: Sub-mature and deciduous forest cover with increasing likelihood away from floodplains and in higher elevations 3. Regeneration: Bare or nearly bare soil with increasing likelihood away from floodplains and in higher elevations 4. Irrigated: Irrigated agricultural lands with increasing likelihood in or near floodplains and in lower elevations 5. Soil: Bare soil with increasing likelihood in or near floodplains and in lower elevations 6. Mixed Ag/Soil: Heterogeneous lands with some irrigated agricultural and bare soil often with some dispersed development 7. Residential: Low to medium density residential developments including rural developments and large-lot urban residential areas 8. Urban: Dense residential developments, urban centers and industrial lands 9. Water: Oceans, lakes, streams and reservoirs, etc… 10. Haze: Clouds partially block view of earth surface 11. Clouds: Clouds completely block view of earth surface 12. Shadow: Dark areas adjacent to Clouds 13. Unclassified: Spectrally indistinguishable areas which can not be classified 14. Built: Impervious surfaces, such as concrete, rooftops, gravel (classified at the fine-scale segmentation level)
Land cover was grouped by land cover classifications for calculation of contiguous land cover classification acres.
1. Forest: Dark Forest, Light Forest and Regeneration land cover classes 2. Agriculture: Irrigated, Soil and Mixed/Ag Soil land cover classes 3. Developed: Residential and Urban land cover classes 4. Clouds: Cloud land cover class 5. Shadow: Shadow land cover class 6. Unclassified: Unclassified land cover class
Land use polygons were generated from the eCognition coarse scale image objects by dissolving objects less than 10 acres in size and not classified as water. While any minimum mapping unit could have been used it would have been difficult if not impossible to classify land uses in areas less than 10 acres (~7 x 7 pixels) with the resolution of the Landsat imagery. Land use polygon acres were calculated as a metric for calculating land use.
The percent developed is the amount of concrete or other developed land cover that is within each land use polygon. The percentage developed of each land use polygon was calculated by overlaying the fine scale developed land cover classification on the dissolved coarse scale general land cover classification.
Development density is the number of individual developments per square mile. The fine scale developed land cover classification was grouped into individual developments. Developments could be of any size ranging from approximately ¼ acre to 169,000 acres in the Seattle metropolitan area. The number of these unique developments in each land use polygon was normalized to a per square mile development density figure.
Adjacent land cover classifications were combined to create contiguous areas of land cover classes. Contiguous land cover classification acres were calculated as a metric for calculating land use.
Adjacent land cover classification groups were combined to create contiguous areas of similar land cover classes. Contiguous land cover group acres were calculated as a metric for calculating land use.
1. Wildland Forest a. Description: Industrial and non-industrial forestlands, parks, municipal watersheds and other forested lands that have very few paved roads or residential developments. b. Definition: At least 640 contiguous forest group acres and no more than 5% developed with a development density of 4 per square mile or less. The land use polygon must be in a forest land cover classification group.
2. Rural Forest a. Description: A mix of forestland types with some dispersed residences. b. Definition: At least 640 contiguous forest group acres and no more than 20% developed with a development density of between 4 and 8 per square mile. Contiguous forest group acres less than 640 and no developments or the land use polygon is greater than 640 acres and no more than 5% developed. The land use polygon must be in a forest land cover classification group.
3. Other Forest: a. Description: Areas that are primarily forest but have too many developments to be considered rural forest. b. Definition: Any remaining land use polygons that are in a forest land cover classification group and not wildland forest or rural forest.
4. Intensive Agriculture: a. Description: Agricultural and livestock lands dominated by irrigated crops or grassland, bare soil and dispersed farm buildings. b. Definition: At lest 640 contiguous irrigated or soil acres and no more than 5% developed with a development density of 9 per square mile or less. Contiguous irrigated or soil class acres less than 640 and less than 1% developed or mixed ag/soil land cover classification and less than 1% developed.
5. Mixed Agriculture: a. Description: A mix of agricultural and livestock lands with some additional residences unrelated to agriculture and an occasional small development. Often includes non-irrigated and cleared lands and occasional industrial buildings. b. Definition: At least 640 contiguous class acres in an agricultural land cover group and no more than 20% developed with a development density of 12 per square mile or less.
6. Other Agriculture: a. Description: Agricultural and cleared lands that have a development density equated to 20 or 40 acre parcels that may be single-family residences, hobby farms or small agricultural operations. b. Definition: Any remaining land use polygons that are in an agriculture land cover classification group and not intensive agriculture or mixed agriculture.
7. Low-Density Residential: a. Description: Large areas of development in suburban and rural settings where parcel sizes are large and the landscape is dominated by roads, homes and commercial buildings. b. Definition: At least 40 contiguous class acres that are in a forest or agricultural land cover classification group and are between 20% and 50% developed.
8. High-Density Residential: a. Description: Large areas of development in dense urban settings or in large rural developments. Small parcel sizes. Around 50% of the land surface is impervious surface like roads, roofs, sidewalks and driveways. b. Definition: Land use polygons that are in the developed land cover classification group and less than 50% developed or less than 40 contiguous class acres and greater than 50% developed or in a non-developed land cover classification group and greater than 50% developed.
9. Urban: a. Description: Dense urban development. Over 50% of the land surface is impervious surface with little vegetation. Airports, industrial parks, urban centers, multi-family residential and very high density residential development. b. Definition: At least 40 contiguous class acres that are in a developed land cover classification group and greater than 50% developed.
10. Water: a. Description: Oceans, lakes, reservoirs and streams. b. Definition: Any land use polygon in a water land cover classification group.
11. Unknown: a. Description: Any land cover that could not be classified do to spectral ambiguity, cloud cover, haze or shadow. b. Definition: Any land use polygon in an unknown land cover classification group.
To decrease the likelihood of misclassification, land use trajectories were developed to create allowable land use change vectors. The primary assumption is that land can only proceed from a more wild to less wild condition. There is evidence that some agricultural lands have been forested and therefore gone to a "more wild" land use but this is believed to be rare.
Final land use designations were calculated as the "least wild" of any preceding land use designations. For example, if a piece of land was designated as Wildland Forest in 1988, Mixed Agriculture in 1996 and Rural Forest in 2004, then the 2004 land use designation was changed to Mixed Agriculture since Mixed Agriculture was defined as "less wild" than Rural Forest. The land use designation trajectories are shown below:
More wild Wildland Forest | Rural Forest | Other Forest | Intensive Agriculture | Mixed Agriculture | Other Agriculture | High-Density Residential | Low-Density Residential | Urban | Water Less wild Unknown
Land use change was calculated by combining (see ArcInfo "combine") the three time steps into a single raster dataset. This raster dataset has land use attributes for each of the three time steps and a unique VALUE for each land use change vector (i.e. Wildland Forest > Rural Forest > Low-Density Residential is VALUE 229). The land use change development attribute was created to quickly symbolize the areas of least and greatest change in development by analyzing the transition from one land use classification to another:
1. No Development Increase: land uses for all three time periods are the same. 2. Minor Development Increase: land use groups for all three time periods are the same. 3. Some Development Increase: land use group has changed from Forest to Agriculture or from Agriculture to Built. 4. Major Development Increase: land use group has changed from Forest to Built 5. Unknown: land use is unknown, cloud/shadow or water in at least one time period and has changed to/from another land use.