METHODS USED:

1. Select Desired Coverages
2. Acquire DLG - Hydrograpy Data
3. Acquire Statsgo data
4. Acquire LULC data
5. Acquire DLG - Road Data
6. Clip coverages to Desired Working Area
7. Create covers for Extraction Area
8. Superimpose Extraction Areas
9. Create Cost Coverages
10. Superimpose Different Scenarios

 

1. Select Desired Coverages

In order to determine potential landfill sites, it is necessary to obtain working coverages corresponding the the selection criteria. These selection criteria require things such as a minimum distance from public roads and a minimum distance from streams. The coverages that were obtained for this purpose include:

1. 1 : 2,000,000 Digital Line Graph Hydrography Data (for stream coverages)
2. 1 : 2,000,000 Digital Line Graph Transportation Data (for road coverages)
3. Landuse Landcover (LULC) Data
4. STATSGO Soils Data

Obtaining the DLG Hydrography Data

The DLG Hydrography Data was obtained by downloading the North Carolina data from the USGS web site (using FTP via graphics). The downloaded file is in a compressed format and thus needs to be unzipped:

alpha61.ce.utexas.edu> gunzip NC.hydro.sdts.tar.gz

The file is transferred in an SDTS (Spatial Data Transfer Standard) format.

First the file must be untarred (broken into its constituent files):

alpha61.ce.utexas.edu> tar -xvf NC.hydro.sdts.tar

blocksize = 128
x NCHYAHDR.DDF, 361 bytes, 1 tape blocks
x NCHYAHYF.DDF, 74047 bytes, 145 tape blocks
x NCHYCATD.DDF, 1855 bytes, 4 tape blocks
x NCHYCATS.DDF, 3803 bytes, 8 tape blocks
x NCHYCATX.DDF, 453 bytes, 1 tape blocks
x NCHYDDSH.DDF, 2363 bytes, 5 tape blocks
x NCHYDQAA.DDF, 1339 bytes, 3 tape blocks
x NCHYDQCG.DDF, 482 bytes, 1 tape blocks
x NCHYDQHL.DDF, 2797 bytes, 6 tape blocks
x NCHYDQLC.DDF, 1397 bytes, 3 tape blocks
x NCHYDQPA.DDF, 947 bytes, 2 tape blocks
x NCHYFF01.DDF, 372 bytes, 1 tape blocks
x NCHYIDEN.DDF, 713 bytes, 2 tape blocks
x NCHYIREF.DDF, 336 bytes, 1 tape blocks
x NCHYLE01.DDF, 427745 bytes, 836 tape blocks
x NCHYNA01.DDF, 12170 bytes, 24 tape blocks
x NCHYNO01.DDF, 69320 bytes, 136 tape blocks
x NCHYPC01.DDF, 19681 bytes, 39 tape blocks
x NCHYSPDM.DDF, 296 bytes, 1 tape blocks
x NCHYSTAT.DDF, 1564 bytes, 4 tape blocks
x NCHYXREF.DDF, 220 bytes, 1 tape blocks

Here is a list of the resulting files:

alpha61.ce.utexas.edu> ls

NC.hydro.sdts.tar NCHYDDSH.DDF* NCHYFF01.DDF* NCHYPC01.DDF*
NCHYAHDR.DDF* NCHYDQAA.DDF* NCHYIDEN.DDF* NCHYSPDM.DDF*
NCHYAHYF.DDF* NCHYDQCG.DDF* NCHYIREF.DDF* NCHYSTAT.DDF*
NCHYCATD.DDF* NCHYDQHL.DDF* NCHYLE01.DDF* NCHYXREF.DDF*
NCHYCATS.DDF* NCHYDQLC.DDF* NCHYNA01.DDF* utmalb.prj
NCHYCATX.DDF* NCHYDQPA.DDF* NCHYNO01.DDF*

These files are translated into useable coverages through the arc command SDTSIMPORT:

Arc: SDTSIMPORT NCHY ncstream

By describing the resulting coverage, we see that the output is in Geographic coordinates:

Arc: describe ncstream

Description of SINGLE precision coverage ncstream

FEATURE CLASSES

The coverage has not been Edited since the last BUILD or CLEAN.

COORDINATE SYSTEM DESCRIPTION

This is projected into the desired albers projection via the following projection file:

input
projection GEOGRAPHIC
datum NAD27
units dd
parameters
output
projection albers
datum NAD83
units meters
parameters
29 30 00
45 30 00
-96 00 00
23 00 00
0.0
0.0
end

This projection filed is employed via the arc command project:

Arc: project

Usage: PROJECT <COVER | GRID | FILE> <input> <output> {projection_file}

{NEAREST | BILINEAR | CUBIC} {out_cellsize}

Arc: project cover ncstream ncstalb2 geoalb.prj

Acquire DLG Transportation Data

Acquire STATSGO Soil Data

STATSGO is a state soil geographic data base that has been created by the US Department of Agriculture. This database describes soil characteristics for areas denoted map units. These map units are further described with a component description. The components are described by layers.

A STATSGO soil coverage of North Carolina was retrieved via anonymous ftp. The site which contained the necessary files is ftp.ncg.ncrs.usda.gov/PUB/STATSGO/UNIX/ARC/ DOCSDATA/NC The necessary file and directory names were first obtained by searching the USDA web site: www.ncg.nrcs.usda.gov.

To convert the downloaded file into usable format the file had to be unzipped via the unix command gunzip.

After unzipping the file, the data was converted to an arc coverage via the command:

import cover <input file> <output file>

The resulting coverage is an Albers projection and is ready for use in Arcview.

5. Acquire Land Use/Land Cover Data

The Land Use/Land Cover (LULC) files are created by the USGS and describe the function of different areas of land. The method used to retrieve the necessary files used both the EPA and USGS web sites, and is described in detail in the following: http://www.ce.utexas.edu/prof/maidment/gishydro/docs/amls/LULC.HTM

Once the desired file names and directories were obtained via the internet, the file was downloaded via anonymous ftp from the site, earth1.epa.gov. The LULC data is contained in 1 x 2 degree map sheets. The map sheet selected for this analysis was the Florence mapsheet.

The resulting file is unzipped via the command:

$: gunzip filename.e00.gz

and converted to an Arc/Info coverage via the command:

Arc: import cover <input file> <output file>

The resulting coverage is an Albers projection and is ready for use in Arcview.

6. Clip Coverages to Desired Working Area:

Once steps 2 - 5 were completed there were four coverages in Albers Projection. The two DLG coverages and the STATSGO coverage contained data for the entire state of North Carolina. The LULC coverage selected contained data for the Florence map sheet, which covers a portion of southeast North Carolina and northeast South Carolina. Due to convenience, file space, and the lack of LULC data for the Charlotte map sheet, the selected study region was the portion of the florence map sheet that covered North Carolina.

The following procedure was used to reduce the coverages obtained in steps 2 - 5 to the selected study area:

Clip the NC soils cover with the florence LULC mapsheet

Arc: clip nc ../../flor nc2

This created a STATSGO soils cover for the area of interest.

Now do the same for the other coverages:

Clip the florence LULC with the clipped NC cover

Arc: clip flor nc/spatial/nc2 flor3

Clipping flor with nc/spatial/nc2 to create flor3.

Now clip Roads Cover with Flor 3 for roads of interest...

Arc: clip dlgnc/uncalb1 flor3 dlgnc/uncalb2 line

Do the same for the DLG stream coverages.

Arc: clip dlgncstr/ncstalb2 flor3 dlgncstr/ncstalb3 line

Now all of our coverages only contain data for the study region of interest.

Creating coverages corresponding to unusable area:

The method employed in this project for choosing viable sites for a low level landfill was a process of elimination. That is, we first considered all of the study area to be valid potential sites. A fraction of these sites were then eliminated corresponding to each regulatory coverage. For example, after the stream coverage was applied, all of the study area was a potential site except for the 90 meter buffer area surrounding each stream. The process of creating exemption coverages was repeated for the following:

1. Road Coverage with 300 meter buffer
2. Stream Coverage with 90 meter buffer
3. Wetland Coverage
4. Urban Coverage
5. Flood Prone Coverage

A. Road Coverage with 300 meter buffer

Buffer Roads:

Arc: buffer dlgnc/uncalb2 dlgnc/bufnca3 # # 300 # #

B. Stream Coverage with 90 meter buffer

Buffer Streams:

Arc: buffer dlgncstr/ncstalb3 dlgncstr/strbuf2 # # 90 # #

C. Wetland Coverage

Wetland Coverage:

The wetland coverage was created within arcview 3. This was accomplished by pulling up the clipped LULC coverage of the area. Once this theme is displayed and active, the query builder was used to select the set of polygons subject to the condition:

LUCODE >= 51 and LUCODE <= 62

The new set created with this condition was then converted to a shapefile which was then added to the view.

D. Urban Coverage

Urban Coverage:

The urban coverage was created by the same method as the wetland coverage. Once the LULC theme was displayed and activated, the query builder was used to select these areas.

The polygons corresponding to urban land use areas was selected subject to the condition:

LUCODE >= 11 and LUCODE <= 17

The new set of polygons created with this condition was then converted to a shapefile which was added to the view.

E. Flood Prone Coverage

Flood Prone Coverage:

The coverage of flood prone map units was created from the STATSGO soils coverage by linking data files for the map units. A detailed analysis of the procedure used to accomplish this is presented in Excercise 5 from Dr. Maidments GIS class. As was mentioned earlier, the STATSGO data is contained in a hierarchical system of map units which are described by components which are further described by layers. The data detailing the flood frequency of different regions is included in the component data. Therefore it is necessary to link the coverage and coverage table (which is in terms of map units) to the layer table. This was accomplished by linking the two tables through the common descriptor, map unit. This is a one to many link because each map unit contains many coverages. In this linkage the mapunit table is the "destination" and the component table the "source".

The regulation describing the relationship between siting a landfill and flood prone lands is that the landfill cannot be sited within the 100 year floodplain of a river. Because the STATSGO data described the chances of flood in terms of "frequent, rare, none", the constraint used in this project was no chance of flooding. Each of the ~25 map units were analyzed and the ones containing layers with a chance of flooding were noted. The query builder was then used to select these map units. The selected map units were then converted to a shape file which was displayed on the view.

8. Superimpose Extraction Areas

Once all the extraction area coverages were created (step 7) these coverages were superimposed to develop a cumulative extraction coverage. This was accomplished by activating each of the extraction coverages simultaneously in Arcview.

While the above coverages corresponded to required extraction areas, there are additional areas that are not desirable for further safety and cost reasons. The one optimization variable looked at in this report was the clay content of the soils.

9. Create "Cost" Coverages

The coverages created consisted of two sets of more restrictive coverages, including land areas with very low clay contents (<10 %) and areas with moderately low clay contents (<30%). The theory behind this selection criteria was that clay materials are very impermeable and thus tend to restrict pollutant migration. In addition, clays are used in landfill construction and the presence of on-site clays reduce the cost of landfill construction.

The clay content coverages were created using a system of table links and the query builder. The link between the map unit and component tables created in step 7E is still active and is used in creating the new coverage. In addition, a link must be created between the component table and the layer table. This link is established with the descriptor "map unit ID". The layer table is the source while the component table is the destination. In creating this link, the link of interest is also made between map unit and layer attribute table. The layer attribute table contained a value for both a high and low estimate of the fraction of the layer composed of clay particles. The map units were grouped into 3 classes by visual estimation.

Very low clay content: These Map Units had Clay Contents of less than 10%.

Moderately Low Clay Content: Percent Clay between 10 and 30 %

Moderate to High Clay Content: Percent Clay > 30 %

These coverages were created by using the query builder to select all map units in each of the classes. The convert to shapefile command was used to convert the selected map units to the specified coverages that were used in Arcview.

10. Superimpose Different Scenarios:

Now that we have all the coverages that we are going to work with, the last step was to combine the coverages in different scenarios to determine which areas are marginally acceptable and optimally acceptable for the siting of a landfill. This step is accomplished in Arcview by activating the unusable coverages and the different clay coverages (except for the high clay content). The land area that is not covered by the coverages is the optimum site areas subject to the constraints used in this project.