A Workable Solution for
the Removal of Sediments From Storage Dams
Storage type dams, regardless of weather they produce hydropower
or are part of an irrigation scheme -- are subject to the
significant and substantive buildup of sediments over decade and
century long timeframes.
It must be noted that once river sediments fill in the upper
levels of a dam (or completely fill in the basin behind the dam)
the dam becomes structurally and functionally useless. This
sedimentation process is part of the operation of all storage
type dams, but in most cases is reversible.
The sedimentation process can be halted or reversed with most
storage type dams, but special engineering processes are
required. The abyssal water pressure inherently existant behind
storage type dams can be used to flush out the accumulated
sediments if the proper use of the dam's existing construction
interfaces are used. However, most storage dams will be rendered
non-functional during the sediment flusing process until it is
redesiged to pass sediments.
Very few modern dams are designed to pass sediments without any
structural impediments. The mixed "run of the river, storage
type" dam that China commissioned on the Yellow River is capable
of passing sediment -- and in many ways is the only one of its
However, any storage type dam can be redesigned to pass
sedimetns if it is shut down.
The way storage dams (and almost all "run of the river" dams)
are built requires that the river or stream be diverted. The
result almost universally is that there are two penstock like
tunnels on each side of the dam that divert the water around the
dam construction area. These tunnels are sealed off with
concrete (and often backed with stone or steel doors) while the
dam is in normal operation.
These sealed off river tunnels are nominally accessible to dam
personnel for structural inspection reasons. Most river access
tunnels are often quite huge, some being up to 250m in radius
and nearly universally at less than a 5 degree downward slope.
There is plenty of room to pass plenty of sediment thru these
The economic cost of filling these river access tunnels with
concrete or conglomerate are high to extremely high. Hence, in
normal operation the river access tunnels are never filled in
and the cost of doing so is almost never factored into normal
dam cost or normal operational running costs of the dam.
So, every storage dam has a free set of channels for flushing
sediments. It can be used.
The process for sediment removal can be broken down in a series
- All of these processes from the beginning need to be open to
the public to see and inspect in detail. It is all to easy to
make huge mistakes here, so all work is best if it is done in
the open. Open sources and open systems here will save lives.
- Fluid dynamics analysis : Do the river re-route channels aim
out in a way that will not harm any civil engineering structures
that are part of the dam downstream? If these channels are badly
oriented, the downstream ends need to be totally redesigned so
that these channels can do their proper work. A lot of the time
there will be many many orientation issues here.
- Cival Engineering : What structures need to be removed for
this sediment flushing to work. Beware, there are going to be
some severe dynamic forces involved here. These hosing, etc
structures need to be removed. Mostly the area within the first
2 kilometres of the dam will be affected.
Repeating this procedure, for a completly clean sweep of sediments
General dam design
The way storage dams are built
Penstock and like structure issues
Fluid dynamics issues
Notable storage dams with this problem
Civil engineering issues downstream
11 June 2013
13 July 2013
Initial Draft 0.25a