Defining buffers setbacks and spreadable acreage

From Wikiagro.com
Jump to: navigation, search

{{#customtitle:Defining Buffers, Setbacks and Spreadable Acreage|Defining Buffers, Setbacks and Spreadable Acreage}}.

Introduction

Each State in the United States has specific setbacks requirements for spreading manure, as part of environmental regulations. These are available at http://www.cares.missouri.edu/snmp/setbacks/index.html . Setbacks may include property lines, ponds, streams, well, etc.

In this session, you will be able to:

  • Define setbacks and buffers for a well, stream and property line.
  • Calculate spreadable acreage for each field, by substracting the buffer/setback area.

 

Exercises

Exercise 01 - Download sample data

GIS gis Init 03 01.jpg

Start GeoAgro GIS by double clicking on its icon at your desktop; you may also run it by using the Windows® Start menu.

The Project Selection window will pop up.

Follow the steps from this link to download the sample datset for this tutorial and create the project 'Sample CNMP' as indicated there.




Exercise 02 - Plan your buffers and setbacks


  1. Zoom in to the farm by double clicking on the “Fields_NRCS” layer Image:Layer_Fields_NRCS.jpgin the left panel. You may use the Zoom Tools to zoom in or out.

  2. Since this farm is in Iowa, we need to apply the following buffers and setbacks according to http://nmplanner.missouri.edu/software/setbacks.asp.

Feature

Type

Distance

Property boundary - irrigated liquid manure

line

100 ft

Drinking water well - not incorporated applications and irrigated manure (vegetative buffer)

point

50 ft

Water source- not incorporated applications and irrigated manure (vegetative buffer)

line

50 ft

Thus, in our farm we will create a 100ft setback from the property line and a 50ft buffer from the well and stream.


Exercise 03 - Create setback from property boundary

What we are going to do first is create a 100ft offset from the property line. Follow the instructions below:

  1. Make the “Tracts” layer active by selecting it.
    Image:Layer_Tracts.jpg
  2. Choose the Point selection tool Image:GIS_gis_Navi_01a_01.jpg in the Navigation panel.

  3. Click anywhere inside the “Tracts” polygon to select it.
    Please click on the image to see it full size

  4. In the Edit Layer's Objects Panel Image:GIS_gis_Edit_05_01.jpg there is a tool called Offset . Click on it.
    LG cnmp bs 04.png

  5. The “Offset” window will come up. Since we want to create another polygon in order to set our setback, we need to click on the “Polygon to Polygon” tab. The option “Don’t modify” must be selected
    .LG cnmp bs 05.png

  6. We want to create a 100ft setback from the property line; this is a new polygon smaller than the tract polygon. Therefore, the offset must be negative: -100. Of course, “Feet” is the unit of measurement. Finally we need to select the target layer. In this case, the “Buffers & Setbacks” layer is the one we are going to use. The picture below shows the right configuration.
    LG cnmp bs 06.png

  7. See the resulting polygon.
    Image:LG_cnmp_bs_07.png



Exercise 04 - Create buffers from stream and well

Now, we are going to create buffers around the Stream and well. Since the explanation is unique for both, we will only focus on the stream buffer.

  1. Make the “Streams” layer active by selecting it. Image:Layer_Streams.jpg

  2. Choose the “Rectangle selection tool” Image:GIS_gis_Navi_01c_01.jpg from availableSelection tools

  3. Draw a rectangle including any part of the stream to select it.
    LG cnmp bs 09.png

  4. In the “Objects Panel” there is a tool called “Buffer”. Click on it.
    LG cnmp bs 10.png


  5. We will define a 50ft offset, “Feet” is the unit of measurement and the “Buffers & Setbacks” layer is the target. See the picture below.
    Image:LG_cnmp_bs_11.png

  6. Repeat the procedure for the 50ft buffer from well. Both, the buffers and setback are shown in the following picture.
    Click here to see the full size image


Exercise 05 - Define the spreadable acreage area


Now we are going to define the spreadable acreage area, by substracting the polygons created from the buffer operations. For this, we will use the “Delete Overlaps” tool.
As you can see, there is a portion of the property line setback which is drawn over the farmstead. We also need to substract it.

Copy

Since we are going to substract all the polygons in the same step, we need first to copy the homestead and the upper left corner Fields into the “Buffers & Setbacks” layer.

  1. Make the “Fields_NRCS” layer active by selecting it.  Image:Layer_Fields_NRCS.jpg
     
  2. Choose the Point selection tool Image:GIS_gis_Navi_01a_01.jpg from the Selection Tools in the “Navigation panel”. By simultaneously pressing the 'CTRL' key, you can select or unselect more than one field.

  3. Select the homestead and the upper left corner Fields.
    LG cnmp bs 14.jpg 

  4. In the Edit Objects Panel Image:GIS_gis_Edit_05_01.jpg click on the tool Copy Object Image:GIS_gis_Edit_05d_01.jpg.
    LG cnmp bs 15.png


  5. Finally, select “Buffers & Setbacks” as target layer and click on copy.
    Image:LG_cnmp_bs_16.png

Substract

Once the copy is completed, we can substract the buffers and homestead/upper left fields from the original property setback area, to define the spreadable acreage area:

  1. Make the Buffers & Setbacks layer active by selecting it.
    Image:Layer_buffers_and_setbacks.jpg

  2. Click on the Point selection tool Image:GIS_gis_Navi_01a_01.jpg and then on the large polygon.

  3. Click on the Edit Objects Panel Image:GIS_gis_Edit_05_01.jpg → and then click on Delete Overlaps tool Image:GIS_gis_Edit_05i_01.jpg.
    We have substracted the stream and well buffer areas and the farmstead/upper left fields from the large polygon, as shown below:Click here to see full size

  4. Now repeat the process to define the spreadable acreage for the upper left field - create setback from property boundary, create stream buffer, copy the largest field to the buffer & setbacks layer, and use the delete overlaps tool.
    Your screen should now show both spreadable acreage areas, as below:
    LG cnmp bs 19.jpg

Copy to destination layer

As final step, you may copy the spreadable acreage areas to the corresponding layer.

  1. Make sure the Buffers & Setbacks is active by clicking on it.
    Image:Layer_buffers_and_setbacks.jpg

  2. Select the two spreadable acreage areas, go to the Edit Objects panel Image:GIS_gis_Edit_05_01.jpg then click on Copy object Image:GIS_gis_Edit_05d_01.jpg and choose “Spreadable Acreage” as target layer.Image:LG_cnmp_bs_20.png

  3. The two spreadable acreage areas are copied to the corresponding layer, as shown below:
    LG cnmp bs 22.jpg



 

Spreadable acreage area

Let’s see what the spreadable acreage area for our farm is.

  1. Make sure that the Layer 'Spreadable Acreage' is active by clicking on it
    Image:Layer_Spreadable_Acreage.png

  2. Select the two spreadable acreage areas, using available Selection tools.

  3. Click on the Info tool Image:GIS_gis_Navi_07_01.jpg in the Navigation toolbar and the spreadable acreage for both fields will be shown, it's 120.30 acres for the larger field, and 2.13 acres for the upper left field.

    click here to see full size