Nigtrogen Pollution Change Due to Land Use Changes in the Plano/Allen area

GISC 6384 - Spring 2005 - Norris Stough

Land Use Change In Plano and Allen, Texas From 1990 to 2000

The Effect on Nitrogen Levels in Storm Water Run Off


Project Objectives

General objectivesApplication of spatial analyst and modeling tools and methodology to data to achieve possible “real-world” applications.

Specific objectivesIdentify areas of land use change in the city of Plano and Allen, Texas and summarize their effect on nitrogen loading in storm water runoff.


Data Sources

North Central Texas Council of GovernmentsLand use shape filesCity boundary shape files

Watershed boundary shape filesSource: www.dfwinfo.com

United States Geological Survey

NED (National Elevation Dataset) raster filesSource: http://seamless.usgs.Gov

http://www.dfwinfo.com/


Steps:1. Conversion from feature data to raster data.2. Determining areas of change in land use type using

raster calculator.3. Reclassification of land use type by nitrogen

loading.4. Zonal sum of nitrogen loading by city and

watershed.5. Creation of drainage basin data for pollutant

summary.6. Zonal sum of nitrogen loading by predefined

drainage basin area.


1990 Land Use RasterFeature to Raster Conversion

Source: North Central Texas Council of Governments


2000 Land Use Raster Feature to Raster Conversion



Determining Areas of Change Raster Calculator

Areas of change were determined by using Raster Calculator. The land use codes for 1990 were subtracted from the land use codes for 2000, resulting in a VAT of the differences.

[lu_00] – [lu_90]

Value of 0 = No Change

All other values = Change in land use

This only works when land use codes remain consistent from 1990 to 2000

Change

No change


Reclassification for Areas of Change

Spatial Analyst Reclassify

The areas of change were then reclassified:– “NoData” for values of 0.– “1” for all other values.

The resulting raster layer could then be used as a filter to identify areas of change in the 2000 land use layer.


Land Use Change Areas


Land Use Change By 2000 Land Use Type

Raster Calculator was used to isolate areas of change from 1990 to 2000 by their 2000 land use codes.

[lu_change] * [lu_00]


Reclassification By Nitrogen Loading Based On Land Use Type

Spatial Analyst Reclassify

Source: http://www.savethebay.org/land/environment/pollution/water.html

Conversion:

Cell Size2 = 2,500 sf

Acre = 43,560 sf

Conversion: 2,500 / 43,560 = 0.057

Pounds (acre) * 0.057 = Pounds (cell)


Nitrogen Load by Land Use After Reclassification


Plano and Allen, Texas Raster File Feature to Raster Conversion



Watershed Raster File Feature to Raster Conversion



Basin GenerationHydrology Watershed

Generating a watershed through the use of elevation data is a common task in GIS.

Watersheds can be generated using pour points to define total upstream area from a point.

However, they can also be generated for local areas of study within a larger watershed by defining basins using a minimum number of cells to determine area.

The process is much the same as used in class, but instead of selecting the “points” options, use “threshold” size.


Original NED Elevation


Allen Land Use Change Overlay on NED Elevation


NED DataHydrology Fill Sinks

2,447 Sinks were Identified and filled.


Flow DirectionHydrology Flow Direction

Drainage channels are easy to identify even at this point.


Flow AccumulationHydrology Flow Accumulation


Basins with Land Use OverlayHydrology Watershed

Basins generated using threshold to generate area.


Zonal Sum By City

Lbs.


Zonal Sum By Watershed

Lbs.


Zonal Sum By Basin

Entertainment & Humor

Nigtrogen Pollution Change Due to Land Use Changes in the Plano/Allen area