9.2 Modern Methods
133
Table 9.4 Positive observable characteristics
Characteristic
Relative
weight (%)
1
Not a low spot
19.30
2
Riprap on the “waterside”
10.50
3
Mild pitch of the dyke on the “dry” side
6.60
4
Extra dyke width, crest width of the embankment
3.85
5
Revetment of the embankment crest (paved, etc.)
3.30
6
Encroached width, toe erosion, etc.
2.75
7
Trees on the dyke on the “waterside”
1.65
8
Easily accessible, not private property, close from residences
1.10
9
Low flow velocity at the toe of the embankment
0.55
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
33
29
27
39
42
38
31
7
18
35
28
30
32
12
25
37
41
36
17
14
34
2
13
22
6
21
5
19
20
23
15
26
3
10
11
4
8
9
16
24
40
1
Fig. 9.7 Segment prioritization based on positive observable characteristics
We were very pleased to see InSAR being referenced in the Expert review of Cadia
tailings facility (http://www.newcrest.com.au/media/market_releases/2019/Report_
on_NTSF_Embankment_Slump.pdf) as we believe space observation data integrated
with the methodologies explained in Chaps. 14 and 15 will help solve many problems
related to tailings dams portfolios risk prioritization and mitigation roadmap.
In the case of Cadia, InSAR data were used a posteriori by the Expert reviewers,
but they are nevertheless very interesting. We take from this that the InSAR measures revealed a significant increase in displacement rate in the three months prior to
failure and that there was a similar trend between calculated and InSAR measured
displacements.