Dataset Identification:
Resource Abstract:
- description: These files include a derived 50 meter spatial resolution Compound Topographic (or Wetness) Index ([CTI or TWI](https://en.wikipedia.org/wiki/Topographic_Wetness_Index))
and Flow Accumulation (as represented by specific catchment area, SCA) calculated from a continuous, transboundary DEM developed
across the Alaska perhumid coastal temperate rainforest (AKPCTR). The extent of this dataset includes all of the Alaska and
Canada watersheds that discharge into southeast Alaska coastal waters, which covers essentially the northern half of the full
PCTR. The transboundary DEM used to calculate the CTI can be here: [link](http://ckan.snap.uaf.edu/dataset/a-continuous-transboundary-50-meter-dem-for-the-alaska-perhumid-coastal-temperate-rainforest-ak06b59)
Flow accumulation is represented by a grid of specific catchment area (SCA), which is the contributing area per unit contour
length using the multiple flow direction D-infinity approach. Unit contour length is equal to the DEM resolution of 50 meters.
**There are two versions of both the CTI and SCA provided:** *CTI_AKPCTR_NoFlowMask.tif and SCA_AKPCTR_NoFlowMask.tif* This
is the resulting CTI file when no masks are applied to the study area before the CTI procedure is run. After the CTI procedure
is run, all glacial areas are masked out, as CTI is not meaningful over glaciers. *CTI_AKPCTR_FlowMask.tif and SCA_AKPCTR_FlowMask.tif*
This is the resulting CTI file where prior to running the CTI procedure, we apply a mask across all active glaciers and all
downslope cells receiving flow from glacially affected cells. These masked cells are excluded from the CTI procedure. This
results in fewer CTI values on the landscape. This dataset is provided to identify cells in the direct downslope path of glaciers
because CTI values for cells receiving upslope accumulation from glaciers may not be reliable due to uncertainties in surface
water flowpaths in glaciated areas. **Processing Steps:** 1. Using the pitremove function from [TAUDEM](http://hydrology.usu.edu/taudem/taudem5/index.html),
filled sinks in the DEM following the method of Planchon and Darboux (2001). 2. (For **_FlowMask* versions only) Mask out
glacial areas and associated downslope cells. Prior to calculating flow direction and flow accumulation, change cells in the
filled DEM to NoData where glaciers exist, using the [Randolph Glacier Inventory version 5.0](https://www.glims.org/RGI/rgi50_dl.html)
raster dataset to identify the presence of glaciers. Cells downslope from the masked glaciers will then also be identified
as NoData in subsequent processing and the final CTI raster. Compute D-infinity slopes and flow direction and flow accumulation
(as specific catchment area) rasters from the filled DEM using TAUDEM D-infinity method. As part of the D-infinity routine,
TauDEM uses the method of Garbrecht & Martz (1997) to resolve flats. 3. The D-infinity slope raster was modified in the
following way: if slope = 0, then change slope value to 0.0001; otherwise leave slope value unchanged. This was done to avoid
dividing by zero when calculating CTI. 4. Compute Compound Topographic Index (CTI) using these steps: `Dsca` = D-infinity
specific catchment area raster `Dslp` = D-infinity slope raster Then, CTI = `Ln(Dsca/Dslp)` 5. Clip the CTI raster to the
Alaska perhumid coastal temperate rainforest (AKPCTR) watershed boundary.; abstract: These files include a derived 50 meter
spatial resolution Compound Topographic (or Wetness) Index ([CTI or TWI](https://en.wikipedia.org/wiki/Topographic_Wetness_Index))
and Flow Accumulation (as represented by specific catchment area, SCA) calculated from a continuous, transboundary DEM developed
across the Alaska perhumid coastal temperate rainforest (AKPCTR). The extent of this dataset includes all of the Alaska and
Canada watersheds that discharge into southeast Alaska coastal waters, which covers essentially the northern half of the full
PCTR. The transboundary DEM used to calculate the CTI can be here: [link](http://ckan.snap.uaf.edu/dataset/a-continuous-transboundary-50-meter-dem-for-the-alaska-perhumid-coastal-temperate-rainforest-ak06b59)
Flow accumulation is represented by a grid of specific catchment area (SCA), which is the contributing area per unit contour
length using the multiple flow direction D-infinity approach. Unit contour length is equal to the DEM resolution of 50 meters.
**There are two versions of both the CTI and SCA provided:** *CTI_AKPCTR_NoFlowMask.tif and SCA_AKPCTR_NoFlowMask.tif* This
is the resulting CTI file when no masks are applied to the study area before the CTI procedure is run. After the CTI procedure
is run, all glacial areas are masked out, as CTI is not meaningful over glaciers. *CTI_AKPCTR_FlowMask.tif and SCA_AKPCTR_FlowMask.tif*
This is the resulting CTI file where prior to running the CTI procedure, we apply a mask across all active glaciers and all
downslope cells receiving flow from glacially affected cells. These masked cells are excluded from the CTI procedure. This
results in fewer CTI values on the landscape. This dataset is provided to identify cells in the direct downslope path of glaciers
because CTI values for cells receiving upslope accumulation from glaciers may not be reliable due to uncertainties in surface
water flowpaths in glaciated areas. **Processing Steps:** 1. Using the pitremove function from [TAUDEM](http://hydrology.usu.edu/taudem/taudem5/index.html),
filled sinks in the DEM following the method of Planchon and Darboux (2001). 2. (For **_FlowMask* versions only) Mask out
glacial areas and associated downslope cells. Prior to calculating flow direction and flow accumulation, change cells in the
filled DEM to NoData where glaciers exist, using the [Randolph Glacier Inventory version 5.0](https://www.glims.org/RGI/rgi50_dl.html)
raster dataset to identify the presence of glaciers. Cells downslope from the masked glaciers will then also be identified
as NoData in subsequent processing and the final CTI raster. Compute D-infinity slopes and flow direction and flow accumulation
(as specific catchment area) rasters from the filled DEM using TAUDEM D-infinity method. As part of the D-infinity routine,
TauDEM uses the method of Garbrecht & Martz (1997) to resolve flats. 3. The D-infinity slope raster was modified in the
following way: if slope = 0, then change slope value to 0.0001; otherwise leave slope value unchanged. This was done to avoid
dividing by zero when calculating CTI. 4. Compute Compound Topographic Index (CTI) using these steps: `Dsca` = D-infinity
specific catchment area raster `Dslp` = D-infinity slope raster Then, CTI = `Ln(Dsca/Dslp)` 5. Clip the CTI raster to the
Alaska perhumid coastal temperate rainforest (AKPCTR) watershed boundary.
Citation
- Title Compound Topographic Index and Specific Catchment Area for the Alaska Perhumid Coastal Temperate Rainforest.
-
- creation Date
2018-05-20T18:19:22.165333
Resource language:
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Metadata data stamp:
2018-08-06T20:05:41Z
Resource Maintenance Information
- maintenance or update frequency:
- notes: This metadata record was generated by an xslt transformation from a dc metadata record; Transform by Stephen M. Richard, based
on a transform by Damian Ulbricht. Run on 2018-08-06T20:05:41Z
Metadata contact
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pointOfContact
- organisation Name
CINERGI Metadata catalog
-
- Contact information
-
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- Address
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- electronic Mail Address cinergi@sdsc.edu
Metadata language
eng
Metadata character set encoding:
utf8
Metadata standard for this record:
ISO 19139 Geographic Information - Metadata - Implementation Specification
standard version:
2007
Metadata record identifier:
urn:dciso:metadataabout:97316806-b4ce-4c72-aea8-0c6091a43d63
Metadata record format is ISO19139 XML (MD_Metadata)