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					Planning the Most Appropriate Forest Road
  Network Considering Soil Drainage and
Stability Using GIS in Shafaroud Watershed-
            Guilan(northern Iran)


Ramin Naghdi, Iraj Bagheri, Esmael GhaJar, Kambiz Taheri,Iraj Hasanzad




                        Dept. of Forestry,
                  College of Natural Resources
                       University of Guilan
                               Iran
                                                                  1
                          18-20,August ,2008
Planning of forest roads in mountain regions

• Traditional method
  Based mainly on :
  Contour lines
  Slope
  Hydrographic attributes

• GIS based method
  all of affecting factors:
  Topographic conditions
  Soil stability
  Landslide hazard
  Land use
  And ….
  Routing, projecting and rapid evaluation     2
Aims
Produce:
           soil drainage map
           soil stability map
To:
           Determine appropriate
           method for planning
           mountainous forest roads
                                      3
       MATERIALS AND METHODS
Studied area:
First district Shafaroud forest
Altitude 100 to 850m
Precipitation 1000mm
Uneven-aged Forest
Type mixed hard wood trees
Growing stock 250 m3/ha
Existing road density of studied district
  21.9m/ha.
                                            4
5
6
Geographic location of Janbesara district

                                            7
8
Method of study :

•   Identify affecting factors in forest roads network planning

•   Produce and categorize map of affecting factors
•   Rating affecting factors in order to produce rout location
    suitable regions map

•   Planning forest roads network

•   Evaluating different road variants, chose the most
    appropriate forest road network and compare it with
    existing road network


                                                                 9
           The affecting factors maps :
•   slope
•   forest type
•   crown cover density
•   hydrographic
•   volume per hectare
•   soil drainage
•   soil stability

were mapped using Arc GIS ver 8.3
                                          10
 In order to produce soil texture map
 land form units :
 slope
 aspect
 altitude


 The drainage and soil stability maps
 were prepared according to FAO guideline
and with regard to the soil texture and aspect
map.

                                                 11
Using Analytical Hierarchy Process

maps were rated in order to determine their
 weight

Then:
 overlaying weighted maps
 suitable regions map for planning roads was
  prepared

                                               12
Using PEGGER program
Route location projected automatically



Finally :

 Compare the two road variants:
• existing roads network
• GIS based network
                                         13
Results



                1200
                           1010
                1000

                800
     area(ha)


                                         535
                600
                                                      303
                400

                200

                  0
                        0_350       350_600       600_850
                                  altitude(m)




                 Frequency distribution of altitude classes


                                                              14
Slope map of Janbesara
                         15
Aspect map of Janbesara
                          16
Land form unites map of Janbesara
                                    17
Soil texture map of janbesara
                                18
Frequency distribution of soil texture factor


  case          classes       Sum(ha)      frequency


   1          Loamy sand       146              8%


   2          Sandy loam       1187             64%


   3        Sandy clay loam    135              7%


   4          Clay loam        381              21%




                                                       19
Forest type map of Janbesara
                               20
volume map of Janbesara
                          21
Soil drainage map of Janbesara
                                 22
                800                                 713
                                        647
                700
                600      491
                500
     area(ha)
                400
                300
                200
                100
                 0
                      high         medium         low
                               drainage classes




Frequency distribution of drainage classes




                                                          23
Classification of soil stability (F.A.O) guide line (1986)


                                      Soil drainage
       Soil texture
                           high          medium                 low

                                Soil stability classification

    Gravel and pebble       1                1                  2

          sand              1                2                  3

   Macro structure-loam     2                2                  3

   Micro structure-loam     2                3                  4

          Clay              3                3                  5

         organic           NA               NA                  5




                                                                      24
Field stability map of Janbesara   25
                               946
                     1000
                      900
                      800
                      700
                                                 505



          area(ha)
                      600
                                                                  401
                      500
                      400
                      300
                      200
                      100
                        0
                            class2           class3           class4
                                     soil stability classes




Frequency distribution of soil stability classes




                                                                        26
suitable regions map for planning roads   27
Road position on soil drainage map
                                     28
                                                               47.2
                        50
                        45
                        40           34.3               33.5
   lenght of roads(%)
                                                                      32.1
                        35                       28.7
                        30   24.9
                        25
                                                                             existing
                        20
                                                                             GIS planned
                        15
                        10
                         5
                         0
                              high              medium         low
                                            drainage classes




Comparison of length of road in percentage on different
drainage classes map for two road networks


                                                                                           29
Roads position on field stability
                                    30
                                       75.5
                           80
                           70   60.4

      lenght of roads(%)
                           60
                           50
                           40
                                                                              existing
                                                                   24
                           30                                                 GIS planned
                                                   15.6 14.5
                           20                                            10
                           10
                           0
                                high             medium            low
                                          soil stability classes




Comparison of length of road in percentage on different soil
stability classes map for two road networks


                                                                                            31
Roads position on slope map
                              32
                           80,00                                     75,9
                                                                             68,1
                           70,00

                           60,00
     Length of Roads (%)




                           50,00

                           40,00
                                                                                                Exist
                                                                                                GIS planned
                           30,00                         22,70

                                                 15,10
                           20,00
                                          9,20
                           10,00   3,90                                              2
                                                                                            0
                            0,00
                                   0-10           10_20              20-45          45-70
                                                         Slope Classes




Comparison of length of road in percentage on different slope
classes map for two road networks
                                                                                                              33
Discussion and Conclusion

•The results of this study show that road network designed using
GIS can be more accessible than the existing road network.




•Therefore due to more accessibility and also shorter skidding
distances, the skidding cost can be expected to be less than
the existing road network.




                                                                   34
•The appropriate condition of the planned road network
based on the drainage and soil stability maps was
approved as long as the rate of road passage from highly
stable areas has shown to be 60 percent in the existing
road network, and 75.5 percent for the GIS based
network.



•In terms of drainage, it has been concluded that the rate of
passage from the areas with suitable drainage is 34 percent
for the planed road, comparing to 25 percent for the existing
road.




                                                                35
Thanks for your attention

                            36

				
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