Articles and Submissions

Included within this page are links to Articles on Dams and how they impact on the surrounding environment. If you have any articles that you feel worth sharing then send them to the Secretary of ADFAS.

Also on this page are Submissions from Organisations and Individuals who wish to share their knowledge or opinions. If you wish to make a submission for inclusion within this web site then please e-mail then to the Secretary of ADFAS. Only correspondence that is constructive and informative to the readers will be included. If articles are deemed not appropriate for inclusion within this web site then the author will be notified of the reasons why.

Articles
Author
Description
The Trouble with Dams
Robert S. Devine
Thirteen ways dams destroy rivers
John Douglas
.
Clutha River Dam Effects
John Douglas
.
Optimx Report
Optimx
Risk Management Consultants
Alexandra Flood Risk Management
Chris Kilby

Manager Policy, Ministry of Civil Defence and Emergency Management.
NB This file is 637 kb PDF file and needs to fully down load before it can be viewed.

Submissions

Organisation
Individual
ADFAS
Laura Wildman
 Lake Hawea Guardians
Dennis Gathard
 
Martin Doyle
 
 

 

Organisation

A
D
F
A
S

Article 1

  • Are you concerned about floods on the Clutha.
  • What you can do about the floods?
  • Do you need help to have your say?

Article 2

  • Why do we need Dams?
  • How can we live with dams so we are not WORSE off?

Article 3

  • What is the problem of silt in the Clutha?
  • What can be done to lesson the Problems of the floods in the Clutha?

Article 4

  • The Dam and our World.
  • What can we ask Contact Energy to do?

Article 5

  • Environment and the Relationships.

Article 6

  • How to make a Submission.
Lake Hawea Guardians
 

 

Individual

Laura Wildman

It sure sounds like they made a mess of your river system.  I can try to answer some of your engineering questions but unfortunately the liability questions are beyond my filed of expertise.  As a non lawyer, I would think you would have a case against the present owner of the dams, since they should have taken over all liability and maintenance issues when they bought the structures.  Since I usually work on small dam projects and these sound like large dams, the only example I can give you around here is that when a larger hydroelectric dam was recently being re-licensed on the Connecticut River in the US, the re-licensing procedure was such that local communities could intervene in the process to make sure that their towns where reimbursed for former damage due to the dam (which in this case was only minor stream bank erosion) and protection from any further damage due to dam operations.  The towns were suitably reimbursed so that they could initiate restoration measures.

Now from an engineering point of view.  Building dams on very dynamic river systems such as the ones you are describing to me can, as your are a first hand witness too, be enormously damaging to the river system, especially the ability of the river to adequately move its "natural" sediment load through the system.  Some of what you are describing to me seems almost irreversible unless the dams are taken out so that the river can naturally move the sediment through the system again.  Without this natural process of sediment transport, keeping up with sediment deposition will be a continual process.  There will be no one time fix and flooding damage will likely only increase over time.  Dredging is a temporary fix.  It will lower flood levels for a short period of time but then the sediment will build right back up.  However now that they have built yet another dam upstream, the primary deposition will likely be in the upstream impoundment.  Dredging does have negative impacts on a river, such as increased turbidity problems, disruption of benthic habitat, impact to vegetated river banks, and potential disruption of the rivers natural armouring processes (that help to create a dynamic equilibrium along the river bed). Now that the dams are in place though, there are not many corrective options left open to you.

The construction of earthen levees or what you are calling earthen banks is a troublesome practice that I have only ever seen cause more damage than good.  If you construct levees to keep out the flood waters but the riverbed keeps on rising due to sediment deposition, at some point you will live in a walled city situated significantly below the elevation of the riverbed.  This has been the case in many areas where levees are used.  If the levees then break during a large flood event (which they all inevitably seem to do) the flood hazard is then tremendous!  In addition the levees stop the river from using its floodplain which it needs to dissipate flood flows.  Without a floodplain the flood flows will just increase in elevation and destructive force (I.e. velocities will be significantly increased in the channel) and flooding problems will just be temporarily moved downstream, until the levees breach.  Pumping rainfall from the non-river side of the levee can also be a problem.  It is very difficult to keep up with the flows and if any electrical problem happens (which is not too uncommon during a major storm)  you are left with a lake of water on your side of the levee.  Anytime we try to engineer our way out of dealing with the mess we have made of a natural system, mother nature usually wins in the end, and we end up with a never-ending maintenance nightmare.  Building terraces is a bit better of an idea but again one that will be difficult to maintain if the riverbed elevation keeps on rising due to sediment deposition.  At least you can create a terrace that drains toward the river.  But remember to incorporated some kind of floodplain.  The river needs to spread out during a flood.

Once again be very wary of any so called solution that is not naturally self maintaining.  The best solution is of course to restore the system back to its pre dam condition before anything gets worse.  In the event that that is not possible then I would think that you have a strong case to put the burden of continual flood maintenance on the owners of the dam.  Stay away from the levee or terrace options if possible.  That could just get your town deeper into trouble.  Dredging is terrible disturbing to a river environment but, short of dam removal, might be your best bet.  After one significant dredge the dam owner may be able to set up some kind of sediment removal system from the river.  I have seen these work on a small scale, like mechanical bed load extractors or continually maintained sediment basins, but your river sounds like it has a lot of sediment and this option may not be possible.  Of course the movement of sediment through your river system was a natural part of how your river maintained dynamic equilibrium and taking sediment out of the system (either by deposition behind a dam or with mechanical means) will create an unbalanced river system downstream, likely leading to excessive downstream erosion and potential ecological imbalance.

I hope some of this has been helpful. 

Laura A.S. Wildman, PE
American Rivers
Northeast Field Office
20 Bayberry Road
Glastonbury, CT 06033

Dennis Gathard

Dennis Gathard. G&G Associates (River Sources) Seattle.

QUESTIONS

(1) Liability and Responsibility

(i) Where does the liability lie?

(ii) Where does the responsibility lie - the Crown who had the dams built, ECNZ / Contact Energy who run the power schemes or with regional government, the Otago Regional Council which has as one of its functions is to review, assess flood hazards with the purpose to minimise and avoid flood damage through the understanding of these hazards?

(2) Sediment Build-up.

(i) Is the removal of sediment a practical solution? That depends on what you mean by practical.  It won't be cheap. I am sure there is a way to move the sediment. 

(ii) Is the removal of sediment a recommended practice of river management" When the reservoir fills, it is an essential element of management 

(3) Earth Bank Wall Protection 

(i) Are earth banks a practical solution?   That depends on how they are designed, what the objective is, where they are placed, etc.  In general they are used for flood protection around the world.  However, you may have seen what is happening on the Mississippi River in the US.  It has earth dikes all along it and flooding is still a problem 

Earth banks that are being built mean the demolition of private and commercial buildings 

(ii) Are earth banks environmentally acceptable?   Any attempt to "tame" the river moves the problem elsewhere. 

(4) Pumps

(i) Pumps are planed to be behind two of the earth banks. What degree of reliability can be placed on pumps?   They usually require a backup power supply, over design incase one fails, and periodic maintenance to ensure that they work when you need them 

(5) Terraces

(i) is the building up of terraces a practical solution?   Yes terraces are a practical solution, but this solution depends on the specific situation.

(6) Maintained of Earth Banks & Pumps

(i) If the flooding is as a result of the dam construction, is the maintenance cost responsibility with those that run the power schemes or with the local community? Generally that is true 

(7) Similar Situations Elsewhere.      

(i) Are there other places in the world with a similar experience that have had or still having the problems that Alexandra experiencing.   Many 

(ii) How do other Power Companies around the world handle these environmental issues?   In the US they get sued frequently.  They Federal Energy Regulatory Commission are responsible for regulating this industry and enforcing environmental requirements.  They do this sometimes. 

(iii) Have you had any problems or concerns on how Southern California Edison or Edison International Energy run their business. Well, they are bankrupt right now, but we have dealt with them frequently 

Sorry if this has got to long and have been asking too many questions. I can only hope that International River Limited can help me. Over 90% of the Alexandra community has similar concerns and finding it difficult to get the answers. The situation is getting to the stage of seriously looking at court proceedings at those that should have acted sooner knowing that the sediment build up was going to be raising the flood level at Alexandra.

Hope your problem is getting better.  Let me know if I can be of specific help.

Dennis Gathard

206.547.4148
547.4052 Fax

Martin Doyle

RESPONSES TO SPECIFIC QUESTIONS ARE GIVEN FOLLOWING THE QUESTIONS BELOW:

QUESTIONS
(1) Liability and Responsibility
(i) Where does the liability lie?.
This will be very different for New Zealand compared to the US. My understanding of the US laws is that the upstream landowners have little or no rights once a downstream dam is in place. Some owners have not even been compensated for land that was put under water in the reservoir. Main thing is that if things weren't addressed when the dam was constructed, then they can't be addressed now. Also, worth considering whether or not the buildings that have been getting flooded were where they were prior to when the dam was in place. Have people built closer to the river since the dam was in place?

(ii) Where does the responsibility lie?
The Crown who had the dams built, ECNZ / Contact Energy who run the power schemes or with regional government, the Otago Regional Council which has as one of its functions is to review, assess flood hazards with the purpose to minimise and avoid flood damage through the understanding of these hazards? At some point, the responsibility is upon the agency in charge of flood extent prediction. In the states, the Federal Emergency Management Agency (FEMA) has to provide maps of where the flood levels lie for the 100-yr flood. These maps have to be updated periodically, but definitely have to be updated if there are major infrastructure changes on the river corridor.
I don't know if similar laws are present in NZ, but I would imagine that some agency should be responsible for updating analysis and showing that floods would be higher for a given flood event.

(2) Sediment Build-up.
(i) Is the removal of sediment a practical solution?
Sediment removal is very very expensive. Particularly via dredging. A more efficient means of removal is if the dam's gates can be opened to allow the water to flush some of the sediment out. Further, many dams are also completely drained for a period of time, and then the upstream sediment is physically removed via excavation equipment. Note the expense is not only in the removal costs, but in the loss of generation time by the hydroelectric facility. This could take on the order of years depending on the size of the dam.

(Ii) Is the removal of sediment a recommended practice of river management"
From what I understand, yes. All dams eventually fill with sediment, and thus, eventually have to be dredged. Also, note that ALL DAMS HAVE A FINITE LIFESPAN. When the dam was commissioned, it will have been commissioned for a certain period of years. After this time, it is subject to review as to what needs to be done to keep this dam operational. Depending on the age of the dam, it may be nearing its projected lifespan. If this is the case, you can make a strong case for removal of sediment as a part of dam operation and maintenance.

(3) Earth Bank Wall Protection
(i) Are earth banks a practical solution? 
Practical over short periods of time, but not a preferred alternative. This is only exacerbating the problem in the long run, as it could potentially lead to more severe floods in the future.
Earth banks that are being built mean the demolition of private and commercial buildings 

(ii) Are earth banks environmentally acceptable?
No. They have been used extensively in the US and Europe (a core part of river channelization). Environmentally, they are a nightmare. Interestingly, following the monster flood on the Mississippi River in 1993, the US Army Corps of Engineers said that river channelization and levees were one of the main reasons for the severity of the flooding. Moral is that they are a quick fix to the problem, but could have dire consequences in the future.

(4) Pumps
(i) Pumps are planed to be behind two of the earth banks. What degree of reliability can be placed on pumps?
This is a bit too far out of my element, so I'll have to sit this question out. 

(5) Terraces
(i) is the building up of terraces a practical solution?
See response to earth bank question above.

(6) Maintenance of Earth Banks & Pumps
(i) If the flooding is as a result of the dam construction, is the maintenance cost responsibility with those that run the power schemes or with the local community?
This is a tricky one. The dam is responsible for the rise in flood stage. But I'm not sure who is responsible for subsequent community costs. I'm guessing that the dam owners are going to be able to shirk responsibility.

(7)  Similar Situations Elsewhere.
(i)  Are there other places in the world with a similar experience that have had or still having the problems that Alexandra experiencing.
I'll have to dig around on this one. I can definitely say that the flood on the Mississippi mentioned above was attributed to the over construction of river works throughout the watershed. However, if I understand it correctly, at no time were the owners of dams ever called to the table to take responsibility for their part in the whole thing.

(Ii) How do other Power Companies around the world handle these environmental issues. They don't. Sometimes the local government will pester them enough to where they will take on some measure to alleviate the environmental damage, but in the end, power prevails over environment. Note that salmon populations in the wester US are at 0.5 to 1 % of what they were 60 years ago. Power companies are not required to compensate the public or the fishing industry. It's quite disgusting in the end. I would recommend the World Commission on Dams report that I mention earlier. This is a great reference for these kinds of issues.

(Iii) Have you had any problems or concerns on how Southern California
Edison or Edison International Energy run there business. I'm not totally familiar with these groups practices, although most of them are trying to get out of paying the cost of removing dams that they profited from for years. It's a sketchy business. 

I hope this information helps some. And again, please feel free to contact me in the future with other questions.

Regards
Martin Doyle
___________________________________________
Martin W. Doyle
Department of Earth and Atmospheric Sciences
Purdue University
1397 Civil Engineering Building
West Lafayette, IN  47907-1397

(phone) 765-494-0258 (Geomorph Lab: Civil 2286)
(fax) 765-496-1210

 


If you require additional information or would like to contact ADFAS then e-mail adfas@alexflood.org.nz