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ArcGIS Forestry Buffer Analysis Lab

Objective

To learn how to • apply buffering using ArcGIS • calculate areas of polygons • convert x­y data coordinates from a table to map features

Background

Forestry workers have discovered the presence of a heron rookery. The District Forester would like you to determine the cost of creating a park around the nests to protect this sensitive habitat. Your first assignment, as GIS specialist, is to create a special reserve zone around the nests. Your second analysis is to create riparian buffer zones on the streams. Obviously streams with fish require greater management consideration than streams with no fish. Further to this, species of fish should also be taken into account. This means that a stream with salmon requires more protection than a stream with guppies. Thus your task will be to create riparian buffers whereby the width is determined by the ‘relative value’ of the stream (i.e. salmon vs. guppies vs. no fish)

General Set­up

• Copy the Lab_2 ­ Buffer Analysis folder from the g: drive to the floppy disk in your U:\ root directory

• Rename the folder yourlastnameLab2 (e.g. CorrinLab2) • Start ArcMap with the New Empty Map option • Add all the data layers from Lab2 (including the Forest Stands.dbf file – this file

contains all the data about the timber types). ** Note, you may need to ‘connect with this new folder’.** Don’t worry if a “warning” appears on the screen saying something about missing spatial reference data and not being able to project the layers.

• Make sure the order of the map layers are as follows: o Tics o Streams o Lakes o Forest o Tenure o Neatline

• Have a look at the data (both the spatial and attribute data) so you understand what you have

• Adjust the colours of the map layers as you see fit (for now … we’ll change them later)

• Save the map document as Buffer in the U:\ yourlastnameLab2 folder • Double click on Layers in the table of contents.

o Change the name to “MyForest” o Set the map and display units to “meters”

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Calculate Area

• Add a field to the attribute table for Forest. • Name the field “Area” and set the type as “float” with precision at 7 (significant digits)

and scale at 1 (decimal places). • Calculate the area of the forest stands in hectares:

§ Right click on the field name (Area) and then select Field Calculator. Click OK at the next pop­up box as we are not worried about undoing this edit. Check the advanced box. Type (or copy/paste from the Lab Resources web page) the following VBA statement in the first text box:

Dim dblArea as double Dim pArea as IArea Set pArea = [shape] dblArea = pArea.area

§ In the bottom text box, type the following to change the area from m 2 to hectares: dblArea/10000

§ Click OK

Join Tables

• If you have closed the table, open the attribute table for the Forest layer and note that FOREST_ID contains the unique identifiers for the forest polygons.

• Open the Forest Stands table and note that the field STAND_ID also contains unique identifiers, but they do not match. What a shame … now we have to edit.

o Change the STAND_ID values from 101 → 1, 102 → 2, 103 → 3,…111 → 11,

o Save edits, stop editing, and o join the Forest Stands table to the Attributes of Forest.

• ** Note, for some reason, after joining the new data from the source table does not display. If this is the case (i.e. the fields are empty), try this

o With the Attributes of Forest table open, start editing o Then immediately stop editing o don’t ask, I don’t know why this works – and yes, every time you open the

table to look at it, you need to do this

Symbology

Ensure the Display tab is selected at the bottom of the table of contents, and the order of the layers is as follows:

• Tics • Streams • Lakes • Forest • Tenure • Neatline

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Adjust the symbology of the layers as follows: • Tics to “cross2” with a size of 8 • Neatline to “Hollow” • Lakes to “Lake” blue • Streams to “River” • Tenure – symbolize with unique values based on the field owner • Forest – symbolized with graduated colours based on age (use the manual

classification and set the values to 50, 100, 150, 200 and 1000); use a colour ramp of light to dark green.

Create a “Point” Layer from Coordinates

The locations of bird nests were determined using GPS and are given in the following table:

NestID Easting Northing 1 5723 3530 2 5830 3491 3 5734 3355 4 5842 3406 5 2501 2993 6 5700 3485

We need to create a new data table named “Nests” that contains the NestID’s as well as the Easting and Northing coordinates. This is a 3­step process: create an empty table, add fields and enter data.

• Create table: Open ArcCatalog and right click on your yourlastnameLab2 folder, select New then dBase table.

o Rename the table Nests.dbf. o Close ArcCatalog (otherwise you may have trouble editing the table in the

next step). • Add Fields: Return to ArcMap and add the Nests data table to your map document.

Open the table and add the following fields: o NestID (short integer) o Xcoord (short integer) o Ycoord (short integer)

• Enter data: Activate the Editor toolbar and start editing. Enter the values from the table above. Save edits and stop editing. Close the Nests table.

The next step is to create a map layer showing these point locations. • Right click on the Nests data table and select Display XY Data

o Make sure your “Xcoord” is selected for the “X Field” and your “Ycoord” is selected for the “Y Field”

o Click OK

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Buffer the Nests

Next, we will explore buffering. First, let’s examine the difference between dissolving (and not dissolving) the boundaries of the buffer features. Note that the Buffer function is located in the Toolbox under Analysis Tools, then Proximity.

• Use the Buffer Wizard and create a 100 metre buffer around all of the nests. Ensure “Dissolve Type” ALL is selected. On the last screen of the Buffer Wizard ensure that the buffer layer will be saved in your yourlastnameLab2 folder and name the layer “Buffer_Yes”.

• Use the Buffer Wizard and create a 100 metre buffer around all of the nests. Ensure “Dissolve Type” NONE is selected. On the last screen of the Buffer Wizard ensure that the buffer layer will be saved in your yourlastnameLab2 folder and name the layer “Buffer_No”.

Note the difference between the two buffer layers (open the data tables and select records). Can you think of a reason to use each method? Which method do you think is used more often?

Let’s look at another buffering option — multiple rings. Suppose we wish to create a reserve of 50 metres around each nest. Now, it would not be proper to log right up to the edge of these reserves as they might blow down (and that would be bad). Perhaps a better approach would be to have a second (additional) buffer around the reserve. In this area we could harvest about 40% of the trees in an attempt to create a windfirm buffer around the reserve.

• Buffer the nests again, but this time choose “Multi Ring Buffer”, again select your Nest data layer as the input layer. Click the folder button to browse to your Lab2 folder and type the name BufferRings, then click Save.. To enter two rings you will need to enter 100 and click the + button, then enter 200 and click the + button. Ensure the “Dissolve Type” ALL is selected. Click OK.

Buffer the Streams

We buffer streams in order to protect water quality and fisheries values. As stated before, some streams have greater value than others; for example, a stream that supports salmon versus a streams that supports no fish whatsoever. The salmon stream should receive greater protection.

Examine the attribute table for the Streams layer. Note that there is a field that records the presence of fish, namely salmon, guppies and none. We will create buffers around these streams, but the width will depend on the fisheries value. An easy way to do this is be to add a field named “width” to the Attributes of Streams table; this field will contain the buffer widths.

• Add a field called “width” to the attribute table with a short integer type. • Enter values as follows: salmon streams get 80; guppies get 40, and none get 20 • Buffer the Streams layer based on the “width” field. Ensure the output layer will be

saved in your yourlastnameLab2 folder as “Streams_Buffer”.

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Map Layout

Create a layout that displays the Nests, Buffer_Rings, Streams, Streams_Buffer, Lakes and Forest layers. No other layers should be displayed. The Buffer_Streams layer should be ‘10% crosshatch’.

Your layout requires the following map elements: legend, title, scale bar (alternating scale bar 2), scale text (1 cm to ‘x’ meters), north arrow, your name and date, and neatline (place around all elements with a yellow background). Refer to last page.

You must set a user­specified scale (e.g. 1:35,000).

Print out your map layout directly from ArcGIS or save it to a jpeg and insert it into a Word document.

Save your Work

Under the File menu, open the map properties dialog box, and set the data source option to “relative paths” (major loss of marks if you don’t do this). Save your map document and exit ArcMap.

Lastly, submit your work to my drop box. First map the drive \\discovery\shares\c\corrin

Then copy yourlastnameLab2 to the drop box.

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