FLOOD09447

• County: Statewide
• Community: Malta Montana
• Basin: Statewide
• Title: Reconnaissance Report Flood Control for Milk River at Malta Montana
• Date: 12/1/1991
• Prepared For: US Army Corps of Engineers
• Floodplain - Doc Type: Floodplain Report/Masterplan

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(a) Kilk River at Alberta, Canada;
(b) Inflow to Fresno Reservoir;
(c) Outflow from Fresno Reservoir;
(d) Kilk River at Havre, Kontana; and
(e) KUk River at Nashua, Kontana.

Because of the regulation effece. of Fresno Reservoir, ite.. (a)
through (c) above cannot be used directly. Instead, a frequency analysis
was done on tha records of inflow to Fresno Reservoir to detenine the
10-, 50-, 100-, and 500-year peak inflows. A unit hydrograph was devel-
oped for the KUk River basin above Fresno Reservoir. Each ordinate used
to define the unit hydrograph was then aultipl1ed by the ratio of the peak
inflow of the selected event to the unit hydrograph peak in order to
obtain the inflow hydro graph for the event. 11Ie resulting 10-, 50-, 100-,
and 500-year inflow hydrographs were then routed through Fresno Reservoir
on a full pool (pool initially at spillway crest) to obtain the corres-
ponding outflow hydrographs.

Using the Fresno Reservoir peak outflows and the results of frequency
analyses on the two downstream gages, Havre and Nashua, regression analy-
ses were I118de for the 10-, 50-, 100-, and 500-year events for the KUk
River below Fresno Reservoir. 11Ie drainage area was used as the indepen-
dent variable. 11Ie regression equations developed from this regional
analysis are as follows:

10-year peak discharge Q10 - 3.707 D&~
50-year peak discharge Q50 - 21.285 D&'~
100-year peak discharge Q100 - 46.095 Dl~
500-year peak discharge Q500 - 308.398 DlJan

The results are displayed graphically in figure 2. Based on the
regression analysis, the discharge-frequency relationships for the
11,762-square-mile Kilk River at Kalta drainage is as follows:

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