Revision History for U.S. Geological Survey Open-File Report 2023-1031 Amy Foxgrover Sediment Deposition, Erosion, and Bathymetric Change in San Francisco Bay, California, 1971–1990 and 1999–2020 ----------------------------------------------------- Posted online March 31, 2023 ----------------------------------------------------- Revised and reposted June 28, 2024 as version 1.1 On page 1, in the section “Abstract,” in the sixth sentence of the first paragraph: This analysis reveals that in the areas surveyed in both the 1980s and 2010s, the bay floor lost about 34 million cubic meters of sediment since the 1980s. 34 million. changed to 20 million ---------------------- On page 6, in the section “Methods,” in the third sentence of the first paragraph, the sentence: After these subembayment DEMs were created and adjusted to account for differences in reference datums and grid cell resolutions, they were differenced (in other words, the 1980s surface was subtracted from the 2010s surface) to reveal patterns of bathymetric change throughout the system. changed to After these subembayment DEMs were created and adjusted to account for differences in reference datums and grid cell resolutions, and corrected for grid interpolation bias, they were differenced (in other words, the 1980s surface was subtracted from the 2010s surface) to reveal patterns of bathymetric change throughout the system. ---------------------- On page 6, in the section “1980s Digital Elevation Model,” after the original second paragraph’s last sentence: The resulting DEMs produced for Suisun, San Pablo, and Central Bays have a resolution of 25 m and for South Bay a resolution of 50 m. and before the original third paragraph’s first sentence: Prior to comparison with the 2010 surveys, adjustments were made to the original bathymetric surface DEMs for each subembayment. the following text was added: The DEMs were then evaluated to determine how well the interpolated surface agreed with the original sounding data. Grid bias was calculated by comparing each individual sounding to its corresponding cell value and the DEMs adjusted by the average amount of grid bias per subembayment. ---------------------- On page 8, in the section “2010s Digital Elevation Model,” in the last paragraph, in between the fourth sentence: In South Bay, rather than using VDatum, the conversion to MLLW was done using a NAVD 88 to MLLW conversion created by NOAA for the 2005 bathymetric survey (Foxgrover and others, 2007). and the fifth sentence: The 2010s 1-m resolution surface DEMs referenced to both MLLW and NAVD 88 and their associated source data are published as a USGS data release (Fregoso and others, 2020). the following sentence was added: Since the 2010s DEMs were primarily derived from multibeam bathymetry, with many soundings per cell, no grid bias correction was applied. ---------------------- On page 9, in the section “Uncertainty in Bathymetric Change,” in the fifth sentence of the fourth paragraph, two revisions were made: Gridding biases of -0.3, -2, and -7 cm were calculated for South, San Pablo, and Suisun Bays, respectively; and, while not removed from the 1980s DEMs, these biases were used in their respective uncertainty calculations (Foxgrover and others, 2004; Jaffe and others, 2007). -0.3, -2, and -7 cm changed to: -0.3, -1.4, and -6.4 cm, respectively and text was revised after the semicolon between the words “respectively” and “and” to: respectively. In some previous studies, grid bias was calculated as part of the uncertainty assessment, but not removed from the source DEMs used for bathymetric change calculations (Jaffe and others, 1998; Cappiella and others, 1999; Foxgrover and others, 2004; Jaffe and Foxgrover, 2006). ---------------------- On page 10, in the section “Bathymetric Change from 1980s to 2010s,” in the second sentence of the first paragraph, the percentages in the sentence: In all, 42 percent of the area surveyed deepened by more than 10 cm and 33 percent shoaled by more than 10 cm. changed to: In all, approximately 40 percent of the area surveyed deepened by more than 10 cm and 35 percent shoaled by more than 10 cm. ---------------------- On page 12, in the section “Sediment Volume Change,” in the second sentence of the first paragraph, the sentence states: The net loss for San Francisco Bay from the 1980s to 2010s was about 34 million cubic meters (Mm^3) of sediment (table 1). 34 million cubic meters (Mm^3) changed to: 20 million cubic meters (Mm^3) ---------------------- On page 12, in the section “Sediment Volume Change,” in the fourth sentence of the first paragraph, the sentence states: Central Bay was the only area with a net sediment gain, 5 Mm^3. 5 Mm^3 changed to: 18 Mm^3 ---------------------- On page 12, in the section “Sediment Volume Change,” in the second sentence of the second paragraph, the sentence states: This rate is largest in Suisun Bay at –2.1 cm/yr, which is net erosional, and least in Central Bay at 0.1 cm/yr, which is calculated to be slightly net depositional. changed to: This rate is largest in Suisun Bay at -2.1 cm/yr and the smallest in South Bay at -0.1 cm/yr, both are net erosional. ---------------------- On page 12, in the section “Sediment Volume Change,” in the last sentence of the second paragraph, the sentence states: The projected volume change from 1983 to 2014, which ranges from -28 to 4 Mm^3 for subembayments and is -46 Mm^3 for the entire 882 km2 surveyed, is a simple, illustrative calculation multiplying the rate-derived volume change rate by the fixed number of 31 years. changed to: The projected volume change from 1983 to 2014, which ranges from -28 to 16 Mm^3 for subembayments and is -34 Mm^3 for the entire 882 km2 surveyed, is a simple, illustrative calculation multiplying the rate-derived volume change rate by the fixed number of 31 years. ---------------------- On page 12, in the section “Sediment Volume Change,” in the sixth sentence of the third paragraph, the sentence states: For example, if Central Bay is thought to have 4 cm of uncertainty in the change values, this results in 10 Mm^3 of volume change, which is twice the magnitude of the net volume change, 5 Mm^3, measured from the 1980s to 2010s. changed to: For example, if South Bay is thought to have 4 cm of uncertainty in the change values, this results in 15 Mm^3 of volume change, which is nearly twice the magnitude of the net volume change, –8 Mm^3, measured from the 1980s to 2010s. ---------------------- On page 12, in the section “Sediment Volume Change,” in the seventh sentence of the third paragraph, the sentence states: Therefore, accounting for a 4 cm uncertainty results in a volume change in the range from –5 Mm^3 (5 Mm^3 measured – 10 Mm^3 uncertainty) to 15 Mm3 (5 Mm^3 measured + 10 Mm^3 uncertainty). changed to: Therefore, accounting for a 4 cm uncertainty results in a volume change in the range from –23 Mm^3 (–8 Mm^3 measured – 15 Mm^3 uncertainty) to 7 Mm^3 (–8 Mm^3 measured + 15 Mm^3 uncertainty). ---------------------- On page 12, in the section “Sediment Volume Change,” in the eighth sentence of the third paragraph, the sentence states: For values of uncertainty greater than 4 cm, Central Bay could be net erosional within error bounds. changed to: For values of uncertainty greater than 2 cm, South Bay could be net depositional within error bounds. ---------------------- On page 13, in “Table 1,” in the “Net volume change (Mm^3)” column and the “Central” row: 5 changed to 18 ---------------------- On page 13, in “Table 1,” in the “Net volume change (Mm^3)” column and the “Total” row: –34 changed to –20 ---------------------- On page 13, in “Table 1,” in the “Mean rate of rate-derived bed level change (cm/yr)” column and the “Central” row: 0.1 changed to 0.2 ---------------------- On page 13, in “Table 1,” in the “Rate-derived volume change rate (Mm^3/yr)” column and the “Central” row: 0.14 changed to 0.52 ---------------------- On page 13, in “Table 1,” in the “Projected volume change for 1983–2014 (Mm^3)” column and the “Central” row: 4 changed to 16 ---------------------- On page 13, in “Table 1,” in the “Projected volume change for 1983–2014 (Mm^3)” column and the “Total” row: –47 changed to –34 ---------------------- On page 13, in “Table 2,” in the “Net volume change (Mm^3)” column and the “Central” row: 5 changed to 18 ---------------------- On page 15, in the “Discussion” section, in the second sentence of the first paragraph states: Although the trends observed are comparable to those from the 1950s to the 1980s, the rate of sediment loss in areas surveyed during both periods decreased fourfold from more than 6 million cubic meters per year (Mm^3/yr) to less than 1.5 Mm^3/yr. Less than 1.5 Mm^3 per year changed to approximately 1.1 Mm^3/yr ---------------------- On page 15, in the “Discussion” section, in the fourth sentence of the first paragraph states: In contrast, only three of the four subembayments had a net loss of sediment from the 1980s to 2010s, with Central Bay gaining 5 Mm^3 of sediment. 5 Mm^3 of sediment changed to 18 Mm^3 of sediment ---------------------- On page 15, in “Table 3,” in the “1980s–2010s——Mean rate of rate-derived bed level change (cm/yr)——Common area” column and the “Central” row: 0.05 changed to 0.21 ---------------------- On page 15, in “Table 3,” in the “1980s—2010s——Mean rate of rate-derived bed level change (cm/yr)——Full extent” column and the “Central” row: 0.05 changed to 0.20 ---------------------- On page 15, in “Table 3,” in the “1980s–2010s—— Rate-derived volume change rate (Mm^3/yr)——Common area” column and the “Central” row: 0.14 changed to 0.52 ---------------------- On page 15, in “Table 3,” in the “1980s–2010s—— Rate-derived volume change rate (Mm^3/yr)——Full extent” column and the “Central” row: 0.14 changed to 0.52 ---------------------- On page 16, in the “Summary” section, in the first sentence of the first paragraph states: Bathymetric surfaces generated from surveys made in the 1980s (1971–1990) and 2010s (1999–2020) indicate that San Francisco Bay lost approximately 34 million cubic meters (Mm^3) of sediment from 1971 to 2020. 34 million cubic meters (Mm^3) changed to 20 million cubic meters (Mm^3) of sediment ---------------------- On page 16, in the “Summary” section, in the first sentence of the second paragraph states: The rate of net sediment loss in San Francisco Bay in areas surveyed in the 1950s, 1980s, and 2010s decreased from more than 6 million cubic meters per year (Mm^3/yr) for the 1950s to 1980s to less than 1.5 Mm^3/yr for the 1980s to 2010s. Less than 1.5 Mm^3/yr changed to approximately 1.1 Mm^3/yr