GIS Demonstration Project 3: Rio Mameyes: GIS-Watershed Analysis Project



Go to:
http://welcome.warnercnr.colostate.edu/class_info/nr505/nr505_06/biocompl
exity/team4/homepage.html
Read the Project Description.
Click on Education Module 4) Physical Features.
Read the description of this module.
We will do this project in ArcExplorer, using the description and maps in the
education module as a guide.
The data for this exercise is located in the GISDemo3 folder and includes the
following:
roads_no_trails
Roads
stream
Boundary
intersect
high_sl_asp
streams_buffer
roads_buffer
high_sus_stream


Let’s walk through the flowcharts to think about what we will do…
Open ArcExplorer.
NOTE: ArcExplorer is a light version of ArcGIS. This exercise will be
modified to use ArcExplorer – which means we cannot do some of
the things described in the online exercise.
PART 1 Road Proximity to Streams/Road and Stream Intersections
Road-stream intersections and roads that exist within 100 meters of a stream are both
used in this analysis as areas that contribute to erosion and increase the sedimentation
of streams. Research shows these two criteria as being major components in the health
of a watershed.
Biocomplexity Workshop: GIS Demonstration Project 3
1

Click the add data button
where the data is located.
-roads
-stream
-Boundary

We can view the attribute data associated with each table. Click on the Select
Feature . From the drop down menu, select Polygon. Draw a polygon around the
entire data layer for Roadsclip. The entire layer should turn yellow.
to insert the following. The instructor will tell you
-Click on the Attributes icon

.
Open the attribute table for each feature in the table of contents and look at the
data. What does it tell you?
-Scroll down and examine the table. Scroll to Road_Class.
If you click on different features on the left hand side of the attribute
table, Notice the value for Road_Class has different types of roads such
as Primary, Secondary, Tertiary, Class 4, and Trail_CNF.
-We can select and classify the Caribbean National Forest trails in this
analysis. This decision is based on the assumption that foot trails contribute a
negligible amount of erosion and sedimentation into the watershed as
compared to roadways.

Be sure the Roads is highlighted. Be sure the Attribute Table is closed.

Click on the Query Builder . Enter the following expression by scrolling to
Road_class, click on it, click on the equals sign and click on Trail_CNF:
Biocomplexity Workshop: GIS Demonstration Project 3
2
 Click on Execute.
-Notice that the trails are now selected in the view. They have all turned yellow.
If you open the Attribute Table, you will notice the top of the table indicates
how many records are selected.
-If you highlight the table in the results table in the Query Builder, the Query
Results buttons become active and you can zoom to the selected trails in your
view.
-To zoom out again, click.
Where are most of the trails located in the Mamayes watershed?
 Click the clear selection button .
 Close the Query Builder
 Add the roads_no_trails.shp to the view.
This layer contains only the roads and the trails have been removed.
Now we can examine the output from the first analysis which shows the following
features:
Biocomplexity Workshop: GIS Demonstration Project 3
3



Areas where roads intersect streams
Areas where roads exist within 100 meters of a stream
Add streams_buffer and road_buffer.
The roads_buffer displays roads with a buffer of 50 meters on each side of the center
line. The stream_buffer displays a buffer of 100 meters on either side of the stream.
The buffers applied to roads and streams don't properly display areas where roads
intersect streams and where roads exist within 100 meters of streams.

Add the intersect layer to the view window. This layer displays our criteria:
-Areas where roads intersect streams
-Areas where roads exist within 100 meters of a stream
-Uncheck the buffer layers and examine the Intersect layer. Only the Intersect and
Boundary layers should be checked
Do you understand what you are looking at? When the two 50 meter buffers intersect
or come in contact at any point, a polygon is formed in this area. Subsequently, the
remaining polygons represent areas where roads intersect with streams and where
roads exist within 100 meters of a stream.
Now, it is time to showcase the results of the analysis so that monitoring groups will
have a visual tool to better predict areas where water quality might be adversely
affected in the watershed.
How might you organize this information into a map layout?

Check layers: roads_no_trails, intersect, streams, and Boundary.

Compare your map to the map on the webpage:
Biocomplexity Workshop: GIS Demonstration Project 3
4
As you can see in the final map of this exercise, the "Areas of Interest" in the legend
represent all of the areas along stream networks where roads intersect or exist within
100 meters of their boundary. This map can be used by monitoring groups as a useful
tool in their search for areas that may pose a detrimental effect on the health of the
watershed.
PART 2 Slope and Aspect
The steep slopes and aspects which are exposed to the prevailing winds in the Mameyes
Watershed have a higher frequency of landsliding.
Maps were created of slope and aspect based on a digital elevation model of the
Mameyes watershed.
The slope layer was reclassified based upon landslide susceptibility. An abstract
prepared by the USGS describes the criteria for a map showing landslide susceptibility in
Biocomplexity Workshop: GIS Demonstration Project 3
5
Puerto Rico. The abstract defines areas of low, moderate, and high susceptibility. The
following criteria will be used to classify the slopes in the Mameyes watershed:



Low Susceptibility: slopes with an angle equal to or less than 12% will equal 1
Moderate Susceptibility: slopes with an angle between 12% and 21% will equal 2
High Susceptibility: slopes with an angle equal to or greater than 21% will equal 3
The aspect map was reclassified for landslide susceptibility due to aspect:



Low Susceptibility: aspects between 202.5 and 292.5 degrees will equal 1
Moderate Susceptibility: aspects between 112.5 and 202.5 degrees, 292.5 and
360 degrees, and 0 and 22.5 degrees will equal 2
High Susceptibility: aspects between 22.5 and 112.5 degrees will equal 3

Be sure and go to the project website and view these maps.
Both the slope and aspect susceptibility maps display areas of concern through their
color coding. Areas in red represent locations of highest concern. These maps can
provide monitoring groups with a useful tool in their search for areas along a watershed
that may pose a detrimental effect on the health of the watershed.
PART 3 Combining Slope and Aspect



Wouldn't it be interesting to combine the features from both maps! We can perform an
operation in ArcExplorer that will allow us to show areas that are common to high,
moderate, and low susceptibility for both slope and aspect.
Examine the flow charts to see how this can be done.
Add high_asp_sl to your view.
Right click on high_asp_sl. Click on Layer Properties. Select the Symbols Tab.
From the drop down symbol menu, select Unique Symbols. Use Grid Code for
Field for Values and select red for the number 1 Value.
Biocomplexity Workshop: GIS Demonstration Project 3
6

Click OK
The data view below has been changed to the color red to show the concurrent areas of
high susceptibility for slope and aspect in regards to landsliding.

Add in high_sus_stream. This layer was derived from buffer the streams 300 meters
and overlayed with the high susceptibility slope and aspect map.
What is the final map displaying?

Examine the final output map on the webpage.
Click on Education Module 5) Water Quality on the webpage.
Work through this module. It is also included below but it will be helpful to look at
the maps on screen as they are in color.
Biocomplexity Workshop: GIS Demonstration Project 3
7
This map displays the results of three separate analyses. These analyses rate impacts on
water quality of areas that are directly adjacent to streams within the Mameyes
Watershed. A description for each of the following subtitles is listed below: Slope and
Aspect, Population Density, and Roads.

Slope and Aspect displays a final map for Education Module #4: Slope and
Aspect. It represents areas of high, moderate, and low susceptibility to
landsliding based on slope percentages and aspects along streams within the
Mameyes Watershed.

Population Density displays a final map for Education Module #3: Population
Dynamics. It represents areas of high, moderate, and low effects on water
quality based on population density along streams within the Mameyes
Watershed.

Roads displays a final map for Education Module #4: Road Proximity to Streams
and Road and Stream Intersections. It represents areas where roads have the
potential to effect water quality along streams within the Mameyes Watershed.
Biocomplexity Workshop: GIS Demonstration Project 3
8
COMPARING AND ANALYZING MAP RESULTS
Slope: At higher elevations of the Mameyes Watershed, the terrain is steeper and more
bedrock is exposed. Also, these steeper slopes are hit hard by hurricanes which bring
high winds and heavy rains and often cause trees to uproot on these slopes where it is
the vegetation which stabilizes the soil. Soil stabilization is important in maintaining
water quality because it prevents excess amounts of sediment from reaching streams.
This is commonly referred to as sedimentation, which can be measured in turbidity tests
at different points along a stream (Jones et al. 2002).
Aspect: Aspect is the direction a slope faces (N, NE, E, SE, S, SW, W) and relates to how
the sun shines on land. In the Mameyes watershed slopes that face northeast, east or
southeast have increased susceptibility to landslides and erosion because they face the
prevailing winds.
Look on the first map of the previous page and see where the highest erosion
susceptibility is within the Rio Mameyes Watershed? What do you think water quality
will be like in these areas?
Don’t forget that there are many other factors that influence water quality? Do you
remember what some of them are? If you still can’t remember, go back to Education
Module 1 and find Measuring the Health of a Watershed.
Population Density: People live in areas where terrain and geography allow, and where
they can access the resources necessary for living. In the Mameyes Watershed, the most
densely populated areas are in the lower part of the watershed along the Rio Mameyes.
How do population settlements affect water quality?
Humans produce waste as do most living species. The difference is that humans produce
more waste than can be degraded by the environment. In realizing our production and
consumption habits, we have invented methods to lessen the impact of our waste on
the natural environment (like recycling and biodegradable products). However, many
products we use have chemicals that do not occur naturally in the environment and
cannot break down easily. Products like cleaning supplies, fertilizers, pesticides, and
other industrial and agricultural by-products also have an impact.
Biocomplexity Workshop: GIS Demonstration Project 3
9
Can you think of how the impact from slope and aspect along with population density
will decrease water quality?
Roads: As you can see in the Roads map, most of the road development is along
streams. These roads are continuous sources of sediment for streams. This sediment
can cause even more damage when it is reactivated during large storm events
(Bruijnzeel et al. 2005, Chappell 2005, Tych et al. 2005). As rain washes sediment into
the rivers, it also washes litter and waste from cars; called runoff. Runoff is commonly
referred to as non-point source pollution (Baskin 1998) because it is difficult to find an
exact source for the accumulated pollutants. Point source pollution is easier to find
because it comes from one source like a factory or a large agricultural establishment.
Reliable water quality data for the Mameyes Watershed is very difficult to find. This may
be due to the very rigorous sampling methods and quality assurance standards required
both in the field and laboratory (Jones et al. 2002). But as you have been exploring in
the previous education modules, there is a real need and beneficial use for such
information.
Despite these problems, there are many monitoring efforts that have been successful in
obtaining useful information for stakeholders and decision-makers alike. Existing
monitoring groups have proven to be invaluable not only for obtaining data, but also
instilling the importance of community, working together and working towards a
common goal.
Explore the EPA Office of Wetlands, Oceans and Watershed and see what Volunteer
Monitoring Groups are doing in and around the country.
http://www.epa.gov/owow/monitoring/volunteer/
Below are two tables that were extracted from the USGS website on water quality data
for the Rio Mameyes Watershed. There are three gages – two are in the higher
elevations and one is in the lowlands. Unfortunately, in trying to cross reference
sources, we found that there was insufficient data in both dates and parameters
measured and a comparison of water quality between the gages would be inconclusive.
Instead of using the rating system and spatially analyzing water quality in the Rio
Mameyes Watershed, we decided to show how the highest susceptibility of aspect and
slope, population and roads may have on water quality throughout the watershed. This
lack of information is also an indication of the amount of work ahead of us in terms of
research and collaboration.
Biocomplexity Workshop: GIS Demonstration Project 3
10
Take a look at the tables in Excel workbook
http://welcome.warnercnr.colostate.edu/class_info/nr505/nr505_06/biocomplexity/tea
m4/project%20website/Module%205/Mamayes_wq.xls.
Be prepared for a lot of numbers. First compare the dates. Look to the left bottom
corner of the page and you will see three tabs. Each of these tabs is a different gage
station. Each row shows a different time and/or date measurements were taken and are
represented by the first column on the far left. The parameters that were measured are
listed in the first row at the top of each worksheet. Look to see which parameters are
measured. What information do you think would be important but is not included?
What do you think this information is used for? Who is it for?
Hint: You might have to go back to your chemistry books to see what the chemical
abbreviations are. One abbreviation you may not be familiar with is cond which stands
for conductivity.
USGS Water Resources of the Caribbean displays a map of the gage stations in
Northeastern Puerto Rico. These are typically not stations that are meant to measure
water quality. The measurements taken there consist of precipitation, water flow, daily
discharge and physical characteristics that can be measured with a meter. While this
information is extremely useful, it is does not represent the chemical properties we are
looking for that cause eutrophication, for example.
Biocomplexity Workshop: GIS Demonstration Project 3
11