Table 10. Pressure sensor elevations and peak high tide delay relative to pre-
dicted time at Anchorage gauge.
Average delay time
Bread Truck Gully
* Arranged by increasing distance from Knik Arm Coast.
Spring Gully and Mortar Gully are generally
tern and fluctuations in the salinity and OBS sig-
first to reach peak high tide because they are
nify tidal flooding and mixing of different water
close to the coast and independent of river influ-
masses, as will be discussed later in more detail.
ence (Table 10). Otter Creek has the greatest lag
Data from a single flood and ebb cycle show
time owing to incomplete drainage of the creek
the basic relationships of water quality param-
between flooding tides and distance from the
eters and inundation (Fig. 32). Initially, as the
coast. During periods of flooding tides from Au-
water level in the gully rises during flood, param-
gust to November, the tide was still rising at Ot-
eters remain at values characteristic of the incom
ter Creek while the rest of the stations re-
corded ebb. This order of peak high tides
between sites varies slightly from month to
month, indicating that additional factors
affect the rate of tidal inundation.
WATER QUALITY PARAMETERS
AND TIDAL FLATS HYDROLOGY
Knowing water quality parameters dur-
ing tidal flood and ebb is critical to under-
standing the interplay of tidal flood waters
and river discharge and its influence on
sedimentation in the Flats. The hydrostation
a. 18 August14 September 1994.
data plotted in Figure 31 bespeak the pa-
rameters controlling sedimentation across
the Flats. These data can be used to deter-
mine critical hydrological elements, such
as duration of inundation (depth), river vs.
tidal water domination (salinity and tem-
perature), and sediment transport (OBS).
For example, Figure 31a presents water
quality data for about 1 month (18 August
to 14 September) where an earlier sequence
of high tides was only high enough to fill
the gullies, and a later sequence flooded
onto the mudflats. The record shows a daily
sinusoidal water temperature pattern when
b. 21 September18 October 1994.
tides are low (29 August1 September). Per-
Figure 31. Hydrostation record at Mortar Gully.
turbations to this regular temperature pat-