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Land Cover changes between the period of 1996 to 2006 within the watershed were calculated by use of land cover layers from NOAA C-CAP (Coastal Analysis Program) data.  The data that was reclassified to either natural or developed and is visually depicted in the maps created below.  Along with land cover change, population change between the years of 1990 and 2000 were calculated at a scale of census blocks.  Population expansion shows by block where population has increased and decreased.  Finally, impervious surfaces and canopy cover layers, both from NOAA C-CAP data, were calculated to see if they follow similar trends as land cover and population changes.

 Population change in King and Snohomish counties have seen dramatic increases in the past few decades (Table 1).   What’s interesting to look at is the greater increases within the watershed compared to the entire county percent population change.  While King has 10.3% and Snohomish has 14.6% increase, the area within the watershed has seen a 36.25% increase in population over a ten year period.  This goes to show how much expansion has occurred away from the greater Seattle area.

*Estimates made from averaging population percent change of King and Snohomish County for that decades increase.

MAP 1

The Population change layer shows areas by block where population has increased and decreased.  Since block boundaries change between census data collection, I had to create an intersect between the two block layers.  In this intersected layer, I created a new field that calculated the difference between the 1990 and 2000 population.  As population between 1990 and 2000 has increased 90,947 peoples, much of this has occurred outside of the MUGA (Municipal Urban Growth Area) (Map1).  Although there is onyl a small section of the MUGA boundaries within the watershed it’s easy to see the heavy increases in population by tract in and around the borders of the MUGA boundaries.  Some areas show some population decrease, but are far outweighed by the denser increasing population areas.  Population increase or decrease of less than 25 peoples were not displayed on the map due to the little impact this has on population change.

MAP 2

LULC changes are a result of reclassifying land use types from C-CAP data into natural and developed land.  Once reclassified, 1996 developed land was erased from the 2006 developed land as to show new areas of developed land (Map 2).  Within this 10 year period there were 29.3 square miles of newly developed land.  The map displays the general clusters of where the change occurred.  Much of this is outside the MUGA boundary.  If you click on the map you can get a larger view of the map.  If you look close you can see large areas of land cover change just outside the border of the MUGA boundaries.

MAP 3

MAP 4

Impervious surfaces in the watershed increased from 1910 square miles to 1924.1 square miles, an increase of 14.1 square miles.  Map 3 displays where the impervious increases occurred.  Interestingly, much of the new impervious surfaces are within the MUGA area.  This may show that although the new developed land layer I created shows much land change outside the MUGA area, the majority of actual building of impervious surfaces (i.e. roads, buildings, ect.) may be within the MUGA boundaries.  Due to the simplified classifications of land cover types, much of the developed in the new land cover layer may be new bare land or land used for agriculture use.  Loss of canopy cover between 1991 to 2001 decreased from 1169 square miles to 1092.5 square miles; approximately 76.5 square miles.  This layer has no close relation to urban sprawl, but is important in showing how much of an impact we as humans can have on our landscape.

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