Canadian Dam Association Bulletin - Summer 2017 - 27

TABLE 1: ENVIRONMENT CANADA RAINFALL RECORDED DURING HURRICANE IGOR
Location

St Lawrence

Bonavista

Lethbridge

Gander Airport

St John's Airport

Depth (mm)

236.2

198.7*

186

124.4

120.2

3.1 WSC Gauge Data
to Lawn and Port Union
The Island of Newfoundland is
generally divided into four (4) hydrological regions; NW, NE, SW and SE,
as illustrated in Figure 3 (Rollings
1999). Within this framework, Lawn
is located in the SE hydrological region
and Port Union is located in the NE
hydrological region. WSC hydrometric
stations located in the area regions are
listed in Table 2.
Transposing data between watershed is accomplished using single
station analysis or by using regional
averaging methods. Each station was
assessed individually as to applicability for transposition. The gauging
station at Rattle Brook did not have a
recorded event for a 2005 flood that
was significant at both Salmonier and
Garnish, which introduced doubt as to
whether it is representative of Lawn.

HYFRAN was used for hydraulic
frequency analysis of the annual
maximum data from the gauged
stations. Results of the frequency
analysis for maximum instantaneous flow for annual exceedance
probability (AEP) events with 100
and 1,000 years periods are presented
in Table  3. Values are also indexed
to the two  (2) year period for comparison with a regional flood equations developed by Government of
Newfoundland and Labrador (RFFA,
1999) that predicted floods with a
return period up to 200 years. The
RFFA estimated 100 year minimum,
median and maximum ratios for the
NE and SE regions as 1.37/1.96/2.81
and 1.25/2.44/3.06, respectively. The
RFFA was not explicit on whether the
ratios were developed on the daily
maximum or maximum instantaneous database.

TABLE 2: ACTIVE WSC HYDROMETRIC STATIONS IN IGOR TRACK
Drainage
Area
(km2)

Period of
Record

42.7

1981-2014

Salmonier River (02ZG003)

115.0

1980-2014

Garnish River (02ZG001)

SE Region

Gauging Station
Rattle Brook (02ZG004)

205.0

1959-2014

NE Region

Inflow hydrographs are prepared
using both spatially distributed rainfall and measured streamflow. At Port
Union, where the watershed is a little
more complicated, HEC-HMS is used
to establish a rainfall - runoff model
and transform the observed rainfall
totals into flow estimates during Igor.
There are some limitations to the
model, including a lack of observed
hydrometric and rainfall data in the
watershed that limit model calibration potential and subsequent validation. At Lawn, where the watershed
is simple, a proxy basin and the index
flood method are used to transpose
the inflow flood from an adjacent
gauged watershed.
At both locations, HEC-HMS was
used to perform reservoir routing
and analysis of the flow during the
hurricane. Input data to the model
included reservoir stage-storage
curves, estimated flood hydrographs
and rating curve of the existing outlet
structures. Head dependent coefficients of discharge were derived
for both spillway and forebay dams
based on the procedure (Brater,
1976). An outflow curve was used to
evaluate how the existing dam and
spillway respond during an inflow
design flood.

Southern Bay
River (02ZJ001)

67.4

1977-2014

Salmon Cove (02ZJ002)

73.6

1983-2014

Comment
No record of
2005 Event

May contain outliers

Independence
Rejected

TABLE 3: FREQUENCY ANALYSIS FOR ANNUAL
INSTANTANEOUS FLOOD (M3/S) SERIES

Figure 3: Rainfall distribution during Hurricane Igor

Canadian Dam Association * Summer 2017

Gauging Station

Drainage
Area
(km2)

Salmonier River
(WSC#02ZG003)

115.0

Garnish River
(WSC#02ZG001)

205.0

Southern
Bay River
(WSC#02JG001)

67.4

Q2
(Q2/Q2)

Q100
(Q100/Q2)

Q1,000
(Q1,000/Q2)

66.8

173

236

(1.00)

(2.59)

(3.53)

52.9

191

323

(1.00)

(3.61)

(6.11)

20.8

100

188

(1.00)

(4.81)

9.04

Frequency
Distribution
LN3
LN3
LN3

27



Table of Contents for the Digital Edition of Canadian Dam Association Bulletin - Summer 2017

Board of Directors
President's Message
Roller Compacted Concrete Buttress at the Site C Clean Energy Project
Hurricane Igor's Impact on Newfoundland Power's Small Hydro
CDA Conference Heads to Kelowna!
CDA Directors & Officers - Call for Nominations
2017 CDA Awards - Call for Nominations
CDA Developing New Ways to Distribute Guidelines
Notice of Annual General Meeting
Time to Renew Your Membership
Buyers' Guide and Trade List
Canadian Dam Association Bulletin - Summer 2017 - intro
Canadian Dam Association Bulletin - Summer 2017 - 1
Canadian Dam Association Bulletin - Summer 2017 - 2
Canadian Dam Association Bulletin - Summer 2017 - 3
Canadian Dam Association Bulletin - Summer 2017 - 4
Canadian Dam Association Bulletin - Summer 2017 - 5
Canadian Dam Association Bulletin - Summer 2017 - 6
Canadian Dam Association Bulletin - Summer 2017 - Board of Directors
Canadian Dam Association Bulletin - Summer 2017 - 8
Canadian Dam Association Bulletin - Summer 2017 - President's Message
Canadian Dam Association Bulletin - Summer 2017 - 10
Canadian Dam Association Bulletin - Summer 2017 - 11
Canadian Dam Association Bulletin - Summer 2017 - Roller Compacted Concrete Buttress at the Site C Clean Energy Project
Canadian Dam Association Bulletin - Summer 2017 - 13
Canadian Dam Association Bulletin - Summer 2017 - 14
Canadian Dam Association Bulletin - Summer 2017 - 15
Canadian Dam Association Bulletin - Summer 2017 - 16
Canadian Dam Association Bulletin - Summer 2017 - 17
Canadian Dam Association Bulletin - Summer 2017 - 18
Canadian Dam Association Bulletin - Summer 2017 - 19
Canadian Dam Association Bulletin - Summer 2017 - 20
Canadian Dam Association Bulletin - Summer 2017 - 21
Canadian Dam Association Bulletin - Summer 2017 - 22
Canadian Dam Association Bulletin - Summer 2017 - 23
Canadian Dam Association Bulletin - Summer 2017 - Hurricane Igor's Impact on Newfoundland Power's Small Hydro
Canadian Dam Association Bulletin - Summer 2017 - 25
Canadian Dam Association Bulletin - Summer 2017 - 26
Canadian Dam Association Bulletin - Summer 2017 - 27
Canadian Dam Association Bulletin - Summer 2017 - 28
Canadian Dam Association Bulletin - Summer 2017 - 29
Canadian Dam Association Bulletin - Summer 2017 - 30
Canadian Dam Association Bulletin - Summer 2017 - 31
Canadian Dam Association Bulletin - Summer 2017 - 32
Canadian Dam Association Bulletin - Summer 2017 - 33
Canadian Dam Association Bulletin - Summer 2017 - 34
Canadian Dam Association Bulletin - Summer 2017 - 35
Canadian Dam Association Bulletin - Summer 2017 - CDA Conference Heads to Kelowna!
Canadian Dam Association Bulletin - Summer 2017 - 37
Canadian Dam Association Bulletin - Summer 2017 - 38
Canadian Dam Association Bulletin - Summer 2017 - 39
Canadian Dam Association Bulletin - Summer 2017 - 40
Canadian Dam Association Bulletin - Summer 2017 - 41
Canadian Dam Association Bulletin - Summer 2017 - 42
Canadian Dam Association Bulletin - Summer 2017 - 43
Canadian Dam Association Bulletin - Summer 2017 - 44
Canadian Dam Association Bulletin - Summer 2017 - 45
Canadian Dam Association Bulletin - Summer 2017 - CDA Directors & Officers - Call for Nominations
Canadian Dam Association Bulletin - Summer 2017 - 47
Canadian Dam Association Bulletin - Summer 2017 - 2017 CDA Awards - Call for Nominations
Canadian Dam Association Bulletin - Summer 2017 - 49
Canadian Dam Association Bulletin - Summer 2017 - CDA Developing New Ways to Distribute Guidelines
Canadian Dam Association Bulletin - Summer 2017 - 51
Canadian Dam Association Bulletin - Summer 2017 - 52
Canadian Dam Association Bulletin - Summer 2017 - Notice of Annual General Meeting
Canadian Dam Association Bulletin - Summer 2017 - Time to Renew Your Membership
Canadian Dam Association Bulletin - Summer 2017 - Buyers' Guide and Trade List
Canadian Dam Association Bulletin - Summer 2017 - 56
Canadian Dam Association Bulletin - Summer 2017 - 57
Canadian Dam Association Bulletin - Summer 2017 - 58
Canadian Dam Association Bulletin - Summer 2017 - 59
Canadian Dam Association Bulletin - Summer 2017 - 60
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