Red River of the North Basin-Wide Modeling Approach
Hydrologic Modeling – HEC-HMS Model Development
Various Tributaries below the Red River of the North at Halstad, MN
100% Submittal Pembina River, ND/MB
Versions:
Date
30 Nov 2014
Description
Initial submittal
Incorporation of submittal comments
Final submittal
Firm Name: St. Paul District Army Corps of Engineers
A. SUBMITTAL OVERVIEW:
The 100% deliverable is an application of the calibrated model to several precipitation
scenarios. The scenarios of interest are:
 10-Day 25-Year scenario from NOAA TP-49 (“S10D025Y_P”)
 10-Day 50-Year scenario from NOAA TP-49 (“S10D050Y_P”)
 10-Day 100-Year scenario from NOAA TP-49 (“S10D100Y_P”)
 10-Day 100-Year effective precipitation scenario derived from NRCS TR-60
runoff (“S10D100Y_R”)
 24-Hour 2-Year scenario from NOAA TP-40 (“S24H002Y_P”)
 24-Hour 5-Year scenario from NOAA TP-40 (“S24H005Y_P”)
 24-Hour 10-Year scenario from NOAA TP-40 (“S24H010Y_P”)
 24-Hour 25-Year scenario from NOAA TP-40 (“S24H025Y_P”)
 24-Hour 50-Year scenario from NOAA TP-40 (“S24H050Y_P”)
 24-Hour 100-Year scenario from NOAA TP-40 (“S24H100Y_P”)
B. SYNTHETIC HMS MODEL EVENTS:
Once the calibration process was completed, a series of synthetic storm
scenarios were simulated. Precipitation amounts for these scenarios were based
on information provided in Technical Paper No. 40 - Rainfall Frequency Atlas of
the Eastern United States for Duration from 30 minutes to 24 hours and Return
Periods from 1 to 100 years (TP40) and Technical Paper No. 49 - Rainfall
Frequency Atlas of the United States. The durations and return periods
simulated are listed below.
 2yr, 5yr, 10yr, 25yr, 50yr, and 100yr – 24hr Rainfall
 25yr, 50yr, and 100yr – 10day Rainfall
During these simulations the loss rate parameters (CN and Ia) were reset to the
initial values determined based on the soil and landuse type. The other
100% Submittal – Pembina River Tributary
1
calibrated unit hydrograph parameters (i.e. R, Tc, …) were adjusted to match the
median calibrated parameters from calibration events. These simulations were
completed using the following rainfall distribution patterns.
 24-hr events - SCS Type II Distribution
 10-day events– Figure 6-4 from Mn Hydrology Guide (Principal Spillway
Hydrograph).
In addition, a synthetic 100yr-10day runoff scenario was developed in an attempt
to simulate conditions similar to those that occur during a spring flood event. To
accomplish this, the following Phase 1 methodology approach was utilized.
1. The approximate composite 24hr CN for the area above Halstad was
determined (using the contributing areas only).
2. A rainfall/precipitation depth grid was developed by determining the
rainfall/precipitation depth required to obtain the resultant runoff depth
shown in TR60 for each cell within the study area based on the calculated
composite 24hr CN for the area above Halstad.
3. HEC-HMS simulation was then completed utilizing this rainfall/
precipitation depth grid, the 24-hr CN values, and the 10-day precipitation
pattern shown in Figure 6-4 from Mn Hydrology Guide (Principal Spillway
Hydrograph).
Note that no depth-area reduction factor was applied on the synthetic events.
Instead, each simulation is listed as a scenario and not a specific frequency
based event.
C. Annual Exceedance Probability Analysis:
Updated discharge-frequency data was obtained for use from the U.S Army Corps of
Engineers and the National Research Council of Canada. Discharge frequency data
was applied to assign annual exceedance probabilities at the USGS streamflow gage at
Walhalla, North Dakota (USGS 05099600/05099500). Walhalla, North Dakota was
selected for flow-frequency comparison because Walhalla is the downstream most
streamflow gage on the mainstem of the Pembina River where it is still appropriate to
apply an analytical flow-frequency distribution.
As part of the National Research Council of Canada’s (NRCC) 2012 “Simulation of
Flood Scenarios on the Lower Pembina River Flood Plains with the Telemac2D
Hydrodynamic Model Phase 3” report, summer (May 1st to September 30th) flowfrequency analysis was generated using data collected at USGS gage 05099600Pembina River at Walhalla, ND. The NRCC generated the summer flow-frequency
curve by applying a Log Pearson Type III distribution using a period of record from
1940-2010 (71 years of record). The NRCC report recommends using a regional skew
at Walhalla of between -0.2 and -0.4 based on the USGS report “Generalized Skew
Coefficients for Flood-Frequency Analysis in Minnesota (Lorenz 1997)” and the national
100% Submittal – Pembina River Tributary
2
skew study included in Bulletin 17B (Plate I). For the NRCC analysis, a regional skew of
-0.4 was adopted from Bulletin 17B with an associated mean square error of 0.302.
The Corps has generated a preliminary all-seasons flow-frequency curve for the
Pembina River at Walhalla using the methodology prescribed by the NRCC. A period of
record from 1940-2014 was adopted for analysis. A Log Pearson Type III distribution
was used to fit a flow-frequency curve to observed annual instantaneous peak flows and
station skew was weighted with a regional skew of -0.4 (MSE 0.302). Flow frequency
analysis used for this study was generated preliminarily in order to provide an indication
of the recurrence interval associated with synthetic rainfall driven events modeled as
part of the Red River Study Phase II. This is a preliminary flow-frequency curve that
should not be directly adopted for design or for floodplain management purposes.
Further consideration of regional skew, potential historic events, and opportunities for
record extension should be accounted for prior to adopting this flow-frequency curve for
applications beyond sensitivity analysis. Tables B.1 and B.2 provides the Flow
Frequency Analysis for the Summer and All-Seasons condition, respectively. Table B.3
provides the flow-frequency results along with the synthetic model results.
To run the model for larger synthetic events, some of the mod puls storage discharge
relationships and breakout flow relationships downstream of Walhalla on the mainstem
of the Pembina River and downstream of Akra on the Tongue River were either
removed from the model or coarsely extended. These relationships do not impact
synthetic event flows modeled at Walhalla. To model the Pembina River downstream of
Walhalla and downstream of Akra on the Tongue River for extreme, synthetic events
(greater than approximately the 3% event at Walhalla) the hydraulic model should be
used to route flows and model breakout flows.
100% Submittal – Pembina River Tributary
3
Table B1. Synthetic Model Run – Summertime Instantaneous Design Discharge for Pembina River at
Walhalla (05099600)
Discharge-Frequency Data - Based on Gage Data
Percent Chance
Exceedance
Return Period
Discharge (cfs)
21,300
0.2
500
15,600
0.5
200
12,000
1.0
100
8,970
2.0
50
7,430
3.0
33.3
5,740
5.0
20
3,820
10.0
10
2,310
20.0
5
1,590
30.0
3.33
842
50.0
2
291
80.0
1.25
164
90.0
1.11
101
95.0
1.05
39
99.0
1.01
Source: National Research Council of Canada. (2012). Simulation of Flood
Scenarios on the Lower Pembina River Flood Plains with the Telemac2D
Hydrodynamic Model Phase 3.
Table B2. Synthetic Model Run – All Seasons Instantaneous Design Discharge for Pembina River at
Walhalla (05099600)
Discharge-Frequency Data - Based on Gage Data
Percent Chance
Exceedance
Return Period
0.2
500
0.5
200
1.0
100
2.0
50
5.0
20
10.0
10
20.0
5
50.0
2
80.0
1.25
90.0
1.11
95.0
1.05
99.0
1.01
Source: Preliminary- USACE St. Paul District
Discharge (cfs)
56,300
42,400
33,400
25,500
16,800
11,500
7,100
2,700
947
533
327
125
100% Submittal – Pembina River Tributary
4
Table B3. Synthetic Model Run – All Seasons Instantaneous Design Discharge for Pembina River at
Walhalla (05099600)
24-hr Rainfall Scenarios
Scenario No.
S24H002Y_P
S24H005Y_P
S24H010Y_P
S24H025Y_P
S24H050Y_P
S24H100Y_P
Peak Discharge [cfs]
4,300
9,000
12,400
17,400
22,100
27,500
Annual Exceedance Probability Based
on Discharge Frequency Curve
Summer
All- Seasons
8.65% (12.5-yr)
2% (50-yr)
1% (100-yr)
0.4% (250-yr)
>0.2% (>500-yr)
>0.2% (>500-yr)
34% (3-yr)
15% (7- yr)
9.0% (11-yr)
4.6% (22-yr)
3.0% (33-yr)
1.7% (59-yr)
10-day Rainfall Scenarios
Scenario No.
S10D025Y_P
S10D050Y_P
S10D100Y_P
Peak Discharge [cfs]
14,200
18,800
24,100
Annual Exceedance Probability Based
on Discharge Frequency Curve
Summer
All- Seasons
0.65% (154-yr)
0.31% (323-yr)
>0.2% (>500-yr)
7.0% (14-yr)
4.0% (25-yr)
2.5% (40-yr)
10-day Runoff Scenario
Scenario No.
S10D100Y_R
Peak Discharge [cfs]
Annual Exceedance Probability Based
on All-Seasons Discharge Frequency
Curve
34,500
0.9% (111-yr)
100% Submittal – Pembina River Tributary
5