Canadian Dam Association Bulletin - Summer 2018 - 23

value of IDF determined using several
methods of calculation should not be
used as the design IDF. Rather, the
range of values should be considered
and discussed in the hydrotechnical
design report.
There are two main types of models for analyzing inflow into and
out of a reservoir, and are discussed
below. There are also combinations
of the methods.

Canadian Dam Association * Summer 2018

Figure 2: Example of a deterministic analysis of reservoir outflow and corresponding
reservoir elevation caused by the reservoir inflow hydrograph (Modified from a slide
provided courtesy of A. Duren)

Percent Annual Chance Exceedance
5,870

5,870

99

95

90

80

50

20

10

5

2

1

0.5 0.2 0.1 0.05 0.01

Top of Dam
5,860

5,850

Spillway Flow
5,840

Elevation (ft, NAVD88)

8.1 Deterministic Analysis
In the context of a streamflow simulation model, deterministic methods
refer to the situation where the rainfall (input) and model parameters
(antecedent moisture; catchment
soils, land use, slope, etc.) are determined using physical laws resulting
in a single calculated value for peak
flow rate and total runoff volume,
given the model input values, at a
particular time during the event.
The IDF target levels for initial consideration and consultation between
owner and regulator, recommended
in CDA (2013), consist of a traditional
deterministic analysis presented in
Table 1. The IDF is commonly determined assuming the reservoir is
filled and there is no routing effect
within the reservoir. In this situation,
the design flood into the reservoir
is equal to the discharge capacity of
the spillway. In some reservoirs, the
dam owner may be able to release
water prior to a flood event or the
reservoir may not be full due to the
demand on the reservoir exceeding
the inflow preceding the storm event.
In this case the reservoir will have a
routing effect and the outflow rate
will be less than the inflow rate as
shown in Figure 2. It is not always
practical to release water from a reservoir prior to a storm event due to
physical equipment restrictions or
regulatory constraints. With a given
inflow hydrograph the corresponding outflow and reservoir elevation
may be calculated deterministically
using appropriate methods. Figure 3
presents a deterministic analysis of
a flood event and resulting reservoir
elevation. A range of reservoir outflow and elevation may be completed

5,830

5,820

5,810

5,800

5,790

5,780

Figure 3: Example of a stochastic analysis of reservoir elevation expressed as
the percent annual chance of exceedance and corresponding reservoir elevation
(Modified from a slide provided courtesy of A. Duren)

by running the calculations several
times using different input values
(sensitivity analysis).
8.2 Stochastic Analysis
A stochastic analysis treats the
input parameters as variables instead
of fixed values as is typically done for
a deterministic analysis. Thousands
of computer simulations are completed using a varying set of input
parameters to determine simulated
flood events. Figure 3 presents a
probabilistic analysis of reservoir

elevation quantiles (the predicted
elevation of the reservoir that corresponds with the selected annual
exceedance probability).
A stochastic technique is used to
extend records, and rely on the statistical properties of a single station
or regional estimates of the parameters (Viessman and Lewis, 1996).
Hartford et al. (2016) indicate that
"Stochastic reservoir inflow is simulated as a random function of time.
This random function may be based
on historical data, may represent a
23



Table of Contents for the Digital Edition of Canadian Dam Association Bulletin - Summer 2018

Board of Directors
President’s Message
Inflow Design Flood Estimation for Reservoirs in British Columbia and Yukon Territory
ICOLD 2018: Canadian Expertise on the World Stage
ICOLD Corner
CDA Will Be Meeting in Quebec City!
CDA Directors & Officers – Call for Nominations
2018 CDA Awards – Call for Nominations
Notice of Annual General Meeting
Time to Renew Your Membership
Clean Energy B.C.'s Operational Excellence Award for Corra Linn Dam
Buyers’ Guide and Trade List
Canadian Dam Association Bulletin - Summer 2018 - Intro
Canadian Dam Association Bulletin - Summer 2018 - cover1
Canadian Dam Association Bulletin - Summer 2018 - cover2
Canadian Dam Association Bulletin - Summer 2018 - 3
Canadian Dam Association Bulletin - Summer 2018 - 4
Canadian Dam Association Bulletin - Summer 2018 - 5
Canadian Dam Association Bulletin - Summer 2018 - 6
Canadian Dam Association Bulletin - Summer 2018 - Board of Directors
Canadian Dam Association Bulletin - Summer 2018 - President’s Message
Canadian Dam Association Bulletin - Summer 2018 - 9
Canadian Dam Association Bulletin - Summer 2018 - Inflow Design Flood Estimation for Reservoirs in British Columbia and Yukon Territory
Canadian Dam Association Bulletin - Summer 2018 - 11
Canadian Dam Association Bulletin - Summer 2018 - 12
Canadian Dam Association Bulletin - Summer 2018 - 13
Canadian Dam Association Bulletin - Summer 2018 - 14
Canadian Dam Association Bulletin - Summer 2018 - 15
Canadian Dam Association Bulletin - Summer 2018 - 16
Canadian Dam Association Bulletin - Summer 2018 - 17
Canadian Dam Association Bulletin - Summer 2018 - 18
Canadian Dam Association Bulletin - Summer 2018 - 19
Canadian Dam Association Bulletin - Summer 2018 - 20
Canadian Dam Association Bulletin - Summer 2018 - 21
Canadian Dam Association Bulletin - Summer 2018 - 22
Canadian Dam Association Bulletin - Summer 2018 - 23
Canadian Dam Association Bulletin - Summer 2018 - 24
Canadian Dam Association Bulletin - Summer 2018 - 25
Canadian Dam Association Bulletin - Summer 2018 - 26
Canadian Dam Association Bulletin - Summer 2018 - 27
Canadian Dam Association Bulletin - Summer 2018 - ICOLD 2018: Canadian Expertise on the World Stage
Canadian Dam Association Bulletin - Summer 2018 - ICOLD Corner
Canadian Dam Association Bulletin - Summer 2018 - CDA Will Be Meeting in Quebec City!
Canadian Dam Association Bulletin - Summer 2018 - 31
Canadian Dam Association Bulletin - Summer 2018 - 32
Canadian Dam Association Bulletin - Summer 2018 - 33
Canadian Dam Association Bulletin - Summer 2018 - CDA Directors & Officers – Call for Nominations
Canadian Dam Association Bulletin - Summer 2018 - 2018 CDA Awards – Call for Nominations
Canadian Dam Association Bulletin - Summer 2018 - Notice of Annual General Meeting
Canadian Dam Association Bulletin - Summer 2018 - Time to Renew Your Membership
Canadian Dam Association Bulletin - Summer 2018 - 38
Canadian Dam Association Bulletin - Summer 2018 - Clean Energy B.C.'s Operational Excellence Award for Corra Linn Dam
Canadian Dam Association Bulletin - Summer 2018 - 40
Canadian Dam Association Bulletin - Summer 2018 - Buyers’ Guide and Trade List
Canadian Dam Association Bulletin - Summer 2018 - 42
Canadian Dam Association Bulletin - Summer 2018 - cover3
Canadian Dam Association Bulletin - Summer 2018 - cover4
Canadian Dam Association Bulletin - Summer 2018 - outsert1
Canadian Dam Association Bulletin - Summer 2018 - outsert2
Canadian Dam Association Bulletin - Summer 2018 - outsert3
Canadian Dam Association Bulletin - Summer 2018 - outsert4
https://www.nxtbook.com/naylor/CDAQ/CDAQ0119
https://www.nxtbook.com/naylor/CDAQ/CDAQ0418
https://www.nxtbook.com/naylor/CDAQ/CDAQ0318
https://www.nxtbook.com/naylor/CDAQ/CDAQ0218
https://www.nxtbook.com/naylor/CDAQ/CDAQ0118
https://www.nxtbook.com/naylor/CDAQ/CDAQ0417
https://www.nxtbook.com/naylor/CDAQ/CDAQ0317
https://www.nxtbook.com/naylor/CDAQ/CDAQ0217
https://www.nxtbook.com/naylor/CDAQ/CDAQ0117
https://www.nxtbook.com/naylor/CDAQ/CDAQ0416
https://www.nxtbook.com/naylor/CDAQ/CDAQ0316
https://www.nxtbook.com/naylor/CDAQ/CDAQ0216
https://www.nxtbook.com/naylor/CDAQ/CDAQ0116
https://www.nxtbook.com/naylor/CDAQ/CDAQ0415
https://www.nxtbook.com/naylor/CDAQ/CDAQ0315
https://www.nxtbook.com/naylor/CDAQ/CDAQ0215
https://www.nxtbook.com/naylor/CDAQ/CDAQ0115
https://www.nxtbookmedia.com