NetMap's Technical Help Guide

9.0 TerrainViewer

 
TerrainViewer: See the "Big Picture"
 
Integrate the "Big Picture" into your TerrainWorks analyses including (1) Watershed Assessments or 2) NetMap Tools with Digital Hydroscapes with the online TerrainViewer.
 
 
Terrainviewer allows one to quickly examine patterns of environmental properties including fish habitats (anadromous, resident), erosion potential, floodplains, wildfire, climate change, and grazing at a variety of scales. In particular, users can quickly search for the highest to lowest values and significant environmental stressor - habitat overlaps over large to small geographic areas.
 
 
To quickly learn how to use the TerrainViewer see Figures 1 through 7.
 
Step 1: select a "scope". The "scope" refers to the area that encompasses your analysis area and it includes Hydrologic Unit Code watersheds from HUC 2 (4 digit) through HUC 5 (10 digit). The scope also applies to US Forest Service jurisdictional boundaries (for individual USFS Regions) and includes: 1) National Forests and 2) Districts. The TerrainViewer has geographic coverage coincident with the Digital Hydroscape. Coverage is expected to increase across the western US and Alaska in 2014.
 
Step 2: a user selects the "scale" of the analysis. The "scale" refers to the grain of the display or analysis. The scale ranges from HUC 4 (8 digit) through HUC 6 (12 digit). The scale must always be smaller than the scope.
 
Step 3: an attribute is selected (#3 in Figure 1) and displayed (#4).
 
Figure 1. The online TerrainViewer interface.
 
 
Figure 2. An example of descending scopes (HUC 2 - 4); selection can continue and extend to HUC 5.
 
 
Figure 3. There are three scale options (HUC 4 - 6). The scale options are reduced in number with diminishing scopes because scale < scope.
 
See the example below that shows how the map display (shallow landsliding) changes as different "scales" are chosen (HUC 4 through 6) with a single HUC 2 "scope" of the Pacific Northwest.
 
Figure 4. An example of selecting a "scope" of HUC 2 Pacific Northwest and a sequence of "scales", selecting the "shallow landslide" attribute. The grain or detail of the analysis increases with increasing HUC level and smaller watersheds.
 
See example below of searching for the top percentile (top 10%) of the attribute in question (shallow landsliding or gullying in less humid areas) and how the locations and grain changes with smaller "scales".
 
Figure 5. A user controls what is displayed with various combinations of "scope" and "scale". In this example, tje scope is HUC 2 (Pacific Northwest) and only the top 10% of the subasin values are displayed at three different "scale" levels (HUC 4, 5 and 6). Notice that with smaller scales more basins are displayed as being in the highest 10% of shallow landslide potential. Note that the shallow landslide attribute can represent different forms of erosion in different landscapes (see data descriptions).
 
 
See example below of searching for habitat - stressor intersections.
Figure 6. An example of a habitat - stressor overlap analysis. An analyst first selects the hightest 10% of shallow landslide - gully erosion risk (top). Second, they search for locations where the highest 10% of shallow landslide - gully erosion risk overlaps with the highest 10% of wildfire severity (mid panel). Third, one searches for the location of intersections for the highest 10% of shallow landslide-gully erosion risk overlaps the highest 10% of fire severity, and where that pair intersects the best 20% of Chinook habitat (note using the best 10% of Chinook habitat did NOT produce any overlaps). The areas of concern are located in southwestern Oregon.
 
 
 
Figure 7. Once critical areas are identified, a user can quickly identify which NetMap Digital Hydroscape dataset is required to dig deeper into locations where landsliding, fires and the best Chinook habitat overlaps. One can use this approach to identify areas for certain types of resource management planning, restoration or conservation.
 
Note that in the TerrainViewer, the anadromous fish distribution matches the  distribution for anadromous habitats that is contained in the "streamnet" mapping (for confirmed fish bearing streams). However, the distribution is extended beyond that to all streams and rivers that are potential habitats based on gradient and flow thresholds in the intrinsic potential model, including those systems where fish are extinct or extirpated. In this approach, all channels that might have been accessible, but are no longer, are included. For source data, see: http://www.streamnet.org/mapping_apps.cfm
 
In Alaska, ADF&Gs Anadromous catalogue is used (for confirmed fish bearing) although the mapped distribution in the TerrainViewer extends beyond that to include all potential habitats as defined in the channel gradient and flow thresholds in available intrinsic potential models.
 
For resident fish, a channel gradient threshold cutoff of 20% is used.
 
Figure 1. Streamnet distribution in the lower 48 states for coho and Chinook, combined (left panel) and steelhead (right panel).
 
 

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