An analysis of a numerical tidal model applied to the Columbia River.

Download
Author
Koehler, Richard Bruce
Date
1988-09Advisor
Thornton, Edward B.
Wu, Chung-Shang
Metadata
Show full item recordAbstract
An implicit finite difference model for predicting flood routing is applied to
the lower Columbia River, where tidal forcing causes flow reversals interacting
with upstream dam flow during small river flow periods. The model is one-dimensional,
unsteady, including lateral inflow and variable bed friction for
different channel sections. A comparison of stages at six stations was made for a
sensitivity analysis. The analysis used a total of 2209 hours of simulated river
stages.
Downstream boundary changes of ±0.5 feet and ±2.0 feet were made to the
Astoria tide stages. Model simulations showed that 70% of the tide difference
appears at Vancouver and Portland, 80% at St. Helens, 85% at Longview, 93% at
Wauna and 95% at Skamokawa. Varying the upstream boundary condition
(Bonneville Dam discharges) by ±10% and ±25% were markedly different from
the downstream boundary changes. Upstream, where the tide influence is weakest,
the tidal cycle is more likely to be "washed out" by the higher flows of the
Columbia. Also these changes fluctuated with the tide cycle. Downstream stations
did not show such differences because of the larger cross section areas of the
Columbia River nearer the mouth and the proximity to the downstream boundary
condition.
The river system was calibrated in a downstream to upstream direction and
used a total of 606 hours of observed river stages. Three periods with distinct river
flow conditions were used in the calibration. Regression analyses of the computed
residual values for each of the stations gave correlation coefficients (r²) less than
0.360. However, cross correlations between residual and computed stages showed
that the two series were highly sinusoidally correlated for all stations. A spectral
estimation of the residuals exhibited very strong peaks at frequencies of 0.081 hr ¹
(12.3 hrs), 0.042 hr¹ (24.0 hrs) and subsequent harmonics of these frequencies.
The residual components are strongly associated with the tidal cycle.
Rights
This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.Collections
Related items
Showing items related by title, author, creator and subject.
-
Laminar boundary layer development downstream of a suction slot
Cigdem, Sabri (1971);Laminar boundary layer development downstream of a suction slot was investigated in a low velocity wind tunnel. In order to observe the effect of suction on the boundary layer, detailed boundary layer profiles were ... -
The security implications of water : prospects for instability or cooperation in South and Central Asia
Radin, Adam J. (Monterey, California. Naval Postgraduate School, 2010-03);This thesis will explore the security implications of water scarcity through an examination of the politics of water in South Asia (India and Pakistan) and Central Asia (Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan, ... -
Fluxes across the west coast resolved by Picket Fence observations during STORMFEST
Bolduc, Steven J. (Monterey, California. Naval Postgraduate School, 1994-09);Meteorological features that force mesoscale weather systems that develop in the central U.S. often form far upstream over the data-sparse Pacific Ocean. It is hypothesized that the temporal and spatial resolution of the ...