Dear all,
I want to assess flood risk or failure risk of dams under future climate change scenarios.
There are about 20 reservoirs in the basin. A hydrologcial model has been used to simulated the rainfall-runoff and routing process driven by GCMs, and reservoir operation from upstream to downstream have also been simulated. Now I have get output of daily inflow, discharege, and reservoir water level fore each reservoir (both future time slices and historical baseline).
How can I measure the flood risk or failure risk of dam (I mean the inflow that exceed the reservoir's storage)?
As the reservoir regulation model has constrained that the reservoir level should not be higher that the normal reservoir level, so I can not meaure it with threshold of reservoir level higher than the designed level of the reservoir. If I use the ‘failure probility’ of P=1-(1-1/T)n, it seems that the dynamic regulation of upstream reservoir is ignored.
So is there any other metrics or literatures I can referer to?
Many thanks.
Dear Hsang
There are a number of ways in which dams fail. For earth embankment dams these can be broadly categorised as:
- Hydraulic (e.g. overtopping of the dam, wave erosion of the upstream face of the dam by wave action, erosion of downstream toe of the earth slope caused by misdirected spillway flows, gullying which can be caused by rainfall erosion of embankment slopes and also traffic)
- Seepage failures where fine soil material is eroded from the downstream slope or foundation and moves towards the upstream slope to form a “pipe” that can lead to the complete failure of the embankment. This is known as “piping” and is a common mode via which earth embankment dams fail
- Structural failures e.g. failure at spillways, abutments and foundations
- Other e.g. Tree growth and animals burrowing in earth dams can lead to failure
When assessing the probability of failure of a dam all the various modes should be considered.
Here is some work from a research project we did on dam break modelling see http://eprints.hrwallingford.co.uk/577/1/CADAM.pdf which also explains how to model dam failures and the causes.
This more recent paper is also useful see: http://eprints.hrwallingford.co.uk/1469/1/HRPP770-A-guide-to-breach-prediction.pdf
This paper may also be of help: https://www.researchgate.net/publication/232941358_Analysis_of_earth_dam_failures_A_database_approach
We have also developed a number of software tools and methods to look at dam breaks see: http://www.hrwallingford.com/expertise/dams-and-reservoirs
To compute the probability of failure of your dams under climate change for a particular design return period (e.g. 1 in 100 year, 1 in 1,000 year of probable maximum flood) you need to:
1. Produce design hydrographs for the design return period and climate change scenario
2. Route the hydrograph through the reservoir
3. Assess the probability of the different modes of failure of the dam for each scenario.
I hope that this is of help.
Darren
Dear Hsang
I forgot to mention that we have tools and methods relevant to support embankment dam breach modelling here: http://www.dambreach.org/
Best regards
Darren
Darren Lumbroso Many thanks for your detailed suggestion. It is helpfull for me.
Dear Dr Hsang
I send you my doctoral thesis entitled: comparative study between rectilinear and non-rectilinear weirs), I worked on the protection of dams against floods.
Best reagrds
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