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image source: http://www.ires.ubc.ca/projects/CWN/

 

 

PROJECT RESULTS

Land Use Map Comparison and Accuracy Analysis

Comparing land uses for the three different years allowed us to quantify where land use changes occured that have the potential to increase surface water nutrient loading. The changes that would have a negative impact on water quality are areas that have changed to an agriculture land use from a non-agricultural land use. The error matrix method identified areas that had changed land use from non-agricultural to agricultural and agricultural to non-agricultural during the two study periods (1966 to 1986 and 1986 to 2001). The results of the error matrix method are summarized below in Table 1.

 
 

Table 1: Flow table of land use changes within the Salmon River Watershed during 1966 – 1986

 
Land Use in 1986
 
Parks & Recreation
Agriculture
Commercial
Residential
TOTAL
Land Use in 1966
Parks & Recreation
3189
3644
651
519
8003
Agriculture
5517
28384
6219
2698
42818
Commercial
6648
7874
3733
495
18750
Residential
318
454
45
495
18750
 
TOTAL
15672
40356
10648
4483
71159

 

 

 

 

 

 

 

 

 

Table 2: Flow table of land use changes within the Salmon River Watershed during 1986 – 2001

 
Land Use in 2001
Residential
Agricultural
Parks & Recreation
Transportation & Communciation
Resource & Industrial
Government & Institutional
Commercial
Total
Land Use in 1986 Residential
7336
7573
255
202
137
138
31
15672
Agricultural
8719
31038
70
439
7
13
70
40356
Parks & Recreation
6641
1056
1
207
2
2730
14
10651
Transportation & Communciation
1897
1895
583
92
8
1
7
4483
Resource & Industrial
618
713
1596
5826
0
113
1
8867

Government & Institutional

359
119
0
861
5
17
25
1386
Commercial
142
15
0
6
0
138
0
301
  Total
25712
42409
2505
7633
159
3150
148
81716

Hints for reading the flow table: totals in the bottom row are the total number of 30 by 30 m raster cells that were designated for each land use in 1986, and the same for 1966 in the total column on the right. The values within the table indicate what each land use cell was designated in the other study year. For example, in 1966 there were 7874 cells that were classified as commerical that in 1986 were classified as agricultural. Or, 709 hectares of commercial land in 1966 was turned into agricultural land in by 1986.

Note: 1986 land use classes Transportation and Communication, Government and Institutional, and Resource and Industrial were not included in the error matrix because the 1966 land use data did not include these classes. Since the main objective of the analysis is to determine the land use change to agriculture over time ignoring these classes will not affect the results.

To compare the results of the error matrix method, overall accuracy is used. Overall Accuracy is defined as the total agreement between the maps (land use that did not change over a time period). We are interested in comparing Agricultural to all other land use classes. The results of this comparison are summarized below in Table 3.

Table 3: Percent land use comparison and accuracy analysis between each time period within the Salmon River Watershed

 
1966:1986
1986:2001
Overall Accuracy
51%
47%
Other to Agriculture
17%
14%
Agriculture to Other
20%
11%
Agriculture constant
40%
38%

More land use changes occurred during the time period 1966 – 1986 when 17% of the land use changed from Other to Agriculture and 20% of the land use changed from Agriculture to Other. Overall approximately 50% of the land did not change uses during both time periods where approximately 40% remained in agricultural use.

Click each map icon below to view the final maps:

Land use changes between 1966 and 1986
Land use Changes between 1986 and 2001

Slope Analysis Results

The Salmon River Watershed is relatively flat in comparison to other parts of British Columbia. Slope within the watershed reaches a maximum of 35% on the banks of tributary streams and the Salmon River.

Click the map icon below to view the final map depicting the results of the slope analysis:

Agricultural areas with a critical slope

Critical Nutrient Source Area Results

Overall there are four critical Nitrate source areas within the Salmon River Watershed during the total time period studied (1966-2001). Fewer critical Nitrate source areas occurred during 1966 – 1986 than during 1986-2001. The critical nitrate source areas are all located adjacent to waterways, and have slopes greater than 5%, and are used as agricultural land.

Click on the map icon below to view the final map depicting the critical nutrient source areas in the watershed:

Critical Nutrient Source Areas