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Western Beach and Ferry Beach, Scarborough
Background geology and characteristics
Annual and seasonal beach profile changes
The beach profiles at Western and Ferry Beach start behind the frontal dune crest. Data collected along Western and Ferry beaches in Scarborough were quite confusing due to the number of times it appears that front and back stakes were used, and changed position. The analysis of the data broke each profile (WS1-WS3) down into a front stake (FS) and back stake (BS).
Data were collected at the WS1 front stake (FS) between 1999-2001. Through the data collection period, the mean profiles show consistent sediment loss along the profile from about 15 m from the pin and farther seaward, with the gain and development of a slight berm at around the 10 m mark (Figure 31). Seasonal data from WS1FS indicate that the summer and winter profile shapes are very similar out to about the 15 m mark (elevation of about 2 m); past this, the summer profile is more voluminous (Figure 32); however, standard deviation data indicate that the winter profile past this point is more variable (up to 40 cm), while the summer profile is more stable, with variations up to about 20 cm (Figure 33a).
For WS1BS, a data set between 2001 and 2006 was collected. Analysis indicates that the profile has been variable, but eroded during the overall time period (Figure 34). Between 2001-2002, the profile gained sediment; from 2002-2003, it remained stable to slightly accretive. From 2003-2004, the profile lost a significant volume of sediment along the majority of its length; maximum loss appears to be on the order of 0.5 m. Between 2004-2005, the profile gained some sediment, and then lost sediment between 2005-2006. On a seasonal basis, data indicate that WS1BS underwent typical summer and winter changes, with the summer mean exhibiting more sediment along the profile than the winter mean (Figure 35). Maximum and minimum profile envelopes indicate that up to 1.5 m of variability in the profile shapes has occurred. Based on standard deviation data, both profiles can be variable vertically (almost up to 60 cm), with maximum variability at 20 m offshore, and around 45 m offshore (Figure 33b).
Data at WS2FS were collected between 1999-2000; the horizontal length of the data set is very short. The mean profiles indicate a loss of approximately 0.5 m of sediment along the length of the profile over the two years (Figure 36). Seasonal data indicate the expected differences in summer vs. winter profile shapes (Figure 37). Summer berm development, evidenced in the standard deviation data, is highly variable, up to 60 cm (Figure 33c).
WS2BS annualized mean data show steady accretion along the entire profile, with the buildup of a dune crest at around 12 m from the pin (gaining about 0.5 m in elevation). Farther offshore, the profile gained much more sediment (Figure 38). The most marked change was between 2004-2005, with over 1 m of accretion. This may be due to the migration of sediment into this area due to the beach nourishment project completed in December 2005. The accretion continued into 2006. Surprisingly, the winter profile for WS2BS shows more sediment volume along the profile than the summer profile (Figure 39). This may be attributed to the influence of the beach nourishment, since the nourishment project was completed during the winter of 2005, this might skew the winter data. Variability for summer and winter data is relatively low until about 15 m, when vertical variability reaches about 50 cm; seaward of this, variability steadily increases for both summer and winter data, with winter standard deviation values peaking at 100 cm (1 m) at about 38 m from the mark, and summer values approaching 140 cm (1.4 m, Figure 33d).
Data at WS3FS were collected between 1999-2003. Mean profiles show a relative stability to slight accretion along the overall profile length (Figure 40). Seasonal profile comparison indicates a slightly more sediment-rich profile during the summer, and slightly greater variability than the winter (Figure 41, Figure 42a).
WS3BS data were collected from 2003-2006. There was little change between 2003-2004, then substantial accretion between 2004-2005, likely due to the influence of nourishment (Figure 43). There was some erosion between 2005-2006. Seasonally, WS3BS shows little variation until around 80 m from the pin (Figure 44); here, the winter profile appears to have slightly more sediment. Standard deviation data indicate a variable dune and berm during the summer (with vertical changes up to 40 cm), with winter variability being much less, on the order of 20-25 cm (Figure 42b).
Data at WS4 were collected from 1999 through 2001; the mark was never surveyed by MGS before it was lost. Profile data indicate that the shoreline underwent erosion between 1999-2000, with slight recovery in 2001, though a large offshore bar that was present in 1999 did not reappear (Figure 45). Seasonal data indicate generally that the winter profile held more sediment than the summer profile shape (Figure 46). Standard deviation data showed relatively high (up to 40 cm) variability along both summer and winter profiles alike (Figure 42c).
Profiles along Western and Ferry Beaches are heavily influenced by the flood- and ebb-tidal formations associated with the Scarborough River. The river, which is flood dominated, tends to store large amounts of sediment within the flood-tidal shoals, adjacent to Ferry Beach. Beach and dune growth (and erosion) is episodic, dependent upon the movement of these shoals. Anthropogenic influence in the form of beach nourishment also has an impact on the shapes of the profiles, especially along Western Beach proper. The nourishment material, over time, should end up in the flood-tidal delta of the river, where sediment is sequestered. Erosion of Western Beach proper will likely continue unless sediment is delivered to the beach at a rate equal to that of the natural shoal bypass rate at the Scarborough River (a good estimate of this is the rate that the dredged river channel shoals).
Last updated on January 3, 2008
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