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Laudholm Beach, Wells
Background geology and characteristics
Annual and seasonal beach profile changes
Profiles collected at Laudholm Beach generally start behind the frontal dune. At LH1, two locations were utilized to initiate profiling; the first for data collected in 2001-2002, and the second for data from 2003-2007 (Figure 110). The beach saw dramatic erosion from 2001 to 2002, with the complete removal of a frontal dune crest. In 2003, a new benchmark was initiated. Erosion occurred along the majority of the profile between 2003-2004, though the dune crest itself appears to have gained slightly in elevation. From 2004-2005, additional erosion occurred, mostly of portions of the profile below 1 m below the pin elevation. 2006 saw erosion of the dune crest and a slight accretion in the offshore (beyond 60 m from the pin). In 2007 additional accretion occurred along the majority of the profile, but predominantly offshore, seaward of the 60 m mark. There is little difference between the summer and winter mean profile shapes until about the 60 m mark - here, the winter profile exhibits better bar formation and offshore sand storage (Figure 111). The 60 m mark may signify some type of ravinement (erosion) surface that inhibits additional landward sediment transport. The winter envelope of variability is also much greater - almost 2 m. Standard deviation data (Figure 112a) show that the winter profile has much more variability, between 40-50 cm, along a large portion of the profile (20 m to 110 m) than the summer profile, which has variability between 20-40 cm along this stretch.
At LH2, data were available for 2003 through 2007. Relatively substantial erosion occurred between 2003 and 2004, while little changes occurred between 2004 and 2005 (Figure 113). The 2006 annualized shape indicates little change in the dune and berm, while there was substantial volumetric change in the offshore, starting at around 50 m from the pin. In 2007, the dune and berm was eroded slightly - on the order of 1-2 m, and there was some additional storage of sediment in the offshore. Seasonally, LH2 exhibits typical summer vs. winter profile shapes, with a better developed berm in the summer profile, and more storage offshore in the winter profile (Figure 114). Based on the standard deviation data, the summer profile is much more variable than the winter (Figure 112b). Winter fluctuation along the entire profile is on the order of 20 cm or less, while the summer variability ranges between 20-40 cm.
The beach at LH3 also had data available for 2003-2007. Similar to LH2, the beach in this area saw substantial erosion along its entire length, from about the -1 m below the pin mark from 2003-2004 (Figure 115). The 2005 mean profile shows that additional erosion occurred, though the dune area remained stable. In 2006, erosion of the berm area continued, while the remaining portions of the profile remained stable. In 2007, the dune appears to have accreted slightly, while the remainder of the profile changed very little. The seasonal comparison of profiles for LH3 indicates greater berm development for the summer profile, while profile envelope minimum and maximums appear to be greater for the winter profile (Figure 116). Standard deviations again indicate, similar to LH2, that the summer variability is much greater than winter along a large portion of the profile (20-140 m from the mark, Figure 112c).
Data were available only from 2003 to 2006 for LH4. Similar to the other profiles, the beach eroded substantially from 2003-2004 (Figure 117). Little change, aside from a slight addition of sediment to the berm, occurred in 2005. The berm eroded to its lowest point in 2006, with the majority of the erosion concentrated in the landwardmost 70 m of the profile. Seasonal data (Figure 118) indicate better berm development, within the first 45 m of the profile, for the summer profile, while the winter profile shows more sand storage offshore, past the 65-70 m mark. Standard deviation data (Figure 112d) show relatively large (50 cm) vertical fluctuations of the berm during the summer at the 45 m mark, while during the winter, the berm only varies around 20 cm.
Profile location LH5 was added in 2006. Overall, it exhibited little change between 2006 and 2007, though there appeared to be a bit of recession in the berm area of the profile, between 1 and 3 m below the pin (Figure 119). Some sediment accreted in the form of nearshore bars farther offshore. Seasonally, LH5 exhibits a distinct difference from other profiles (Figure 120). The winter shape has more sediment volume in the berm, and farther offshore than the summer mean shape. Standard deviation data (Figure 112e) show a slight bit more variation in the berm elevation (almost 40 cm) in the winter, versus around 20 cm in the summer. These characteristics may relate to the proximity of LH5 to more abundant gravel and peat deposits on the profile compared to the others that have sand over more of the profile.
Laudholm Beach has experienced some severe periods of erosion of the frontal dune and the berm is often composed of gravel and cobbles in the winter. Variability of the profiles seaward of the dune is somewhat atypical due to the mixed grain sizes of sand, gravel, and cobbles. The larger sediment sizes are sorted and transported more in the winter than in the summer hence some of the profile variability in winter is due to the higher wave energy. Summer sand often covers the cobble surface on the central portions of the profiles as sand bars migrate ashore from beyond the extent of profiling.
Last updated on January 3, 2008
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