13.3 Field Study Methods
213
Fig. 13.3 Using smoke bombs to trace tunnel connectivity
Hillslope
Depth(m)
Horizontal distance(m)
Electrical resistance(ohm m)
1
1 0
10
20
30
40
50
60
70
80
90
100
0
0
5
10
15
20
25
100
1000
Fig. 13.4 Electrical resistance measured along a soil profile in which a tunnel typically shows high
electrical resistance