Overview README file for the entire repository

Hourly observed and six-minute predicted water levels at the end of Scripps Pier, Station 9410230 in La Jolla, California, USA, are extracted from the National Oceanic and Atmospheric Administration's (NOAA's) Center for Operational Oceanographic Products and Services (CO-OPS) database. During the extracted record, an acoustic sensor was used until 2014 (Aquatrak air acoustic sensor), when it was fully replaced by a microwave radar water level sensor (Xylem WaterLOG H-3611i, first installed in 2013). A pressure sensor (GE Druck PDCR 4010) was used as a backup to fill in data gaps. All water level sensors were leveled and data quality controlled. Predictions are generated from harmonic constituents of the record dating back to 1924. The sensors at the end of the Scripps pier are less than 40km away from all beach monitoring sites and measure the water level above a water column that is approximately 6m deep. Regional, non-tidal effects (e.g. El Niño) are included in the observed water levels and will be similar between sites and the gauge. However, local effects may vary between the monitoring sites and the gauge observations, particularly eddy activity and wave set down (or some wave setup, if waves are large). Note that when creating shoreline water level estimates, the user must account for wave setup and runup that is not observed in deeper water at the gauge. The tidal-only information provided by the predictions may also vary slightly from the monitoring sites and can be estimated using tidal models (e.g. TPXO, ADCIRC).

Nearshore waves at Cardiff and Solana Beaches. To facilitate modeling of beach profile change, wave characteristics in 10m depth spaced 100m alongshore were extracted from the Scripps Institution of Oceanography’s wave Monitoring and Prediction (MOP) system for the California coastline (http://cdip.ucsd.edu/). Wave estimates along the coastline are produced using a linear spectral refraction model initialized with 2-D spectral estimates from multiple Datawell directional buoys. For swell waves (0.04–0.08 Hz) the model is initialized with deep water buoys located seaward of the Channel Islands. For sea waves (0.09-0.5 Hz) the model is initialized with buoys located inside the islands along the mainland shelf break. Each MOP point in 10m depth has a corresponding backbeach point, defining a MOP line. MOP line orientations are chosen to minimize the distance from the backbeach to the 10m contour. Hindcast time series of wave height (H_s), peak (T_p) and average (T_a) wave period, peak (D_p) and mean (D_m) wave direction, and radiation stress estimates (onshore S_{xx} and alongshore S_{xy}) are provided at each transect line relative to the MOP estimated shore normal (orientation also provided). Additionally, time series of wave energy, E, and low-order moment directional Fourier coefficients (a_1, b_1, a_2, b_2, in true compass “from” coordinates), as a function of wave frequency, are provided at the seaward end of each MOP line on the 10m depth contour. The 10m depth wave model output mirrors the information provided by directional wave buoys or a pressure-velocity meter (PUV), and can be treated in the same way as the spectral data from these instruments when defining boundary conditions for sediment transport models. Occasionally, wave model output is degraded due to buoy malfunctions and is flagged using the "waveFlagPrimary" variable. (Good model output has waveFlagPrimary = 1.) WHEN USING THE MODEL OUTPUT IT IS IMPERATIVE THAT THE WAVEFLAGPRIMARY IS CONSIDERED IN CONJUNCTION WITH THE WAVE ESTIMATES. The nearshore wave hindcasts were validated using shallow water wave buoys (20m depth). The hourly buoy-driven wave hindcasts show significant skill at most validation sites, but prediction errors for individual swell or sea events can be large. Model skill is high at the sites in north San Diego County. Overall, the buoy-driven model hindcasts have relatively low bias such that averaging over space or time is useful for minimizing noise. Best practices for using the 100m spaced, 10m depth MOP wave hindcasts, as boundary conditions for beach change models, are not well established. It is not known if alongshore averaging or smoothing of the 100m-spaced MOP hindcasts (eg. on typical sea, swell or infragravity wavelength scales) is beneficial for beach change model stability. Space-time wave averaging questions must be explored by investigators based on their specific modeling needs and goals. Using the fixed shore normal S_{xy} estimates with 2D beach change models that predict changes in shoreline orientation is internally inconsistent, so additional second-order rotations of the S_{xy} values (or direct recalculation of S_{xy} using the a_2 and b_2 Fourier coefficients in compass coordinates) based on modeled shore normal changes, will be required.

Nearshore waves at Torrey Pines Beach. To facilitate modeling of beach profile change, wave characteristics in 10m depth spaced 100m alongshore were extracted from the Scripps Institution of Oceanography’s wave Monitoring and Prediction (MOP) system for the California coastline (http://cdip.ucsd.edu/). Wave estimates along the coastline are produced using a linear spectral refraction model initialized with 2-D spectral estimates from multiple Datawell directional buoys. For swell waves (0.04–0.08 Hz) the model is initialized with deep water buoys located seaward of the Channel Islands. For sea waves (0.09-0.5 Hz) the model is initialized with buoys located inside the islands along the mainland shelf break. Each MOP point in 10m depth has a corresponding backbeach point, defining a MOP line. MOP line orientations are chosen to minimize the distance from the backbeach to the 10m contour. Hindcast time series of wave height (H_s), peak (T_p) and average (T_a) wave period, peak (D_p) and mean (D_m) wave direction, and radiation stress estimates (onshore S_{xx} and alongshore S_{xy}) are provided at each transect line relative to the MOP estimated shore normal (orientation also provided). Additionally, time series of wave energy, E, and low-order moment directional Fourier coefficients (a_1, b_1, a_2, b_2, in true compass “from” coordinates), as a function of wave frequency, are provided at the seaward end of each MOP line on the 10m depth contour. The 10m depth wave model output mirrors the information provided by directional wave buoys or a pressure-velocity meter (PUV), and can be treated in the same way as the spectral data from these instruments when defining boundary conditions for sediment transport models. Occasionally, wave model output is degraded due to buoy malfunctions and is flagged using the "waveFlagPrimary" variable. (Good model output has waveFlagPrimary = 1.) WHEN USING THE MODEL OUTPUT IT IS IMPERATIVE THAT THE WAVEFLAGPRIMARY IS CONSIDERED IN CONJUNCTION WITH THE WAVE ESTIMATES. The nearshore wave hindcasts were validated using shallow water wave buoys (20m depth). The hourly buoy-driven wave hindcasts show significant skill at most validation sites, but prediction errors for individual swell or sea events can be large. Model skill is high at the sites in north San Diego County. Overall, the buoy-driven model hindcasts have relatively low bias such that averaging over space or time is useful for minimizing noise. Best practices for using the 100m spaced, 10m depth MOP wave hindcasts, as boundary conditions for beach change models, are not well established. It is not known if alongshore averaging or smoothing of the 100m-spaced MOP hindcasts (eg. on typical sea, swell or infragravity wavelength scales) is beneficial for beach change model stability. Space-time wave averaging questions must be explored by investigators based on their specific modeling needs and goals. Using the fixed shore normal S_{xy} estimates with 2D beach change models that predict changes in shoreline orientation is internally inconsistent, so additional second-order rotations of the S_{xy} values (or direct recalculation of S_{xy} using the a_2 and b_2 Fourier coefficients in compass coordinates) based on modeled shore normal changes, will be required.

Nearshore waves at Imperial Beach. To facilitate modeling of beach profile change, wave characteristics in 10m depth spaced 100m alongshore were extracted from the Scripps Institution of Oceanography’s wave Monitoring and Prediction (MOP) system for the California coastline (http://cdip.ucsd.edu/). Wave estimates along the coastline are produced using a linear spectral refraction model initialized with 2-D spectral estimates from multiple Datawell directional buoys. For swell waves (0.04–0.08 Hz) the model is initialized with deep water buoys located seaward of the Channel Islands. For sea waves (0.09-0.5 Hz) the model is initialized with buoys located inside the islands along the mainland shelf break. Each MOP point in 10m depth has a corresponding backbeach point, defining a MOP line. MOP line orientations are chosen to minimize the distance from the backbeach to the 10m contour. Hindcast time series of wave height (H_s), peak (T_p) and average (T_a) wave period, peak (D_p) and mean (D_m) wave direction, and radiation stress estimates (onshore S_{xx} and alongshore S_{xy}) are provided at each transect line relative to the MOP estimated shore normal (orientation also provided). Additionally, time series of wave energy, E, and low-order moment directional Fourier coefficients (a_1, b_1, a_2, b_2, in true compass “from” coordinates), as a function of wave frequency, are provided at the seaward end of each MOP line on the 10m depth contour. The 10m depth wave model output mirrors the information provided by directional wave buoys or a pressure-velocity meter (PUV), and can be treated in the same way as the spectral data from these instruments when defining boundary conditions for sediment transport models. Occasionally, wave model output is degraded due to buoy malfunctions and is flagged using the "waveFlagPrimary" variable. (Good model output has waveFlagPrimary = 1.) WHEN USING THE MODEL OUTPUT IT IS IMPERATIVE THAT THE WAVEFLAGPRIMARY IS CONSIDERED IN CONJUNCTION WITH THE WAVE ESTIMATES. The nearshore wave hindcasts were validated using shallow water wave buoys (20m depth). The hourly buoy-driven wave hindcasts show significant skill at most validation sites, but prediction errors for individual swell or sea events can be large. Model skill is fair at Imperial Beach owing to a combination of swell energy sensitivity to shadowing by the offshore islands and poorly resolved model bathymetry south of the U.S-Mexico border. Overall, the buoy-driven model hindcasts have relatively low bias such that averaging over space or time is useful for minimizing noise. Best practices for using the 100m spaced, 10m depth MOP wave hindcasts, as boundary conditions for beach change models, are not well established. It is not known if alongshore averaging or smoothing of the 100m-spaced MOP hindcasts (eg. on typical sea, swell or infragravity wavelength scales) is beneficial for beach change model stability. Space-time wave averaging questions must be explored by investigators based on their specific modeling needs and goals. Using the fixed shore normal S_{xy} estimates with 2D beach change models that predict changes in shoreline orientation is internally inconsistent, so additional second-order rotations of the S_{xy} values (or direct recalculation of S_{xy} using the a_2 and b_2 Fourier coefficients in compass coordinates) based on modeled shore normal changes, will be required.

Raw (quality controlled) sand elevations at Torrey Pines Beach. An ATV with rear shocks removed and constant tire pressure (to maintain a consistent distance from the GNSS antenna to the sand level below), was used to measure the subaerial beach at low tide, while a 3 wheeled push dolly (with GNSS antenna mounted on a fixed-height mast) was used from the low-tide waterline to chest deep wading depths. A personal watercraft (Yamaha Waverunner, but here the more familiar term jet ski will be used) equipped with 192kHz acoustic sonar, sea surface thermistor (for speed of sound calculation) and GNSS antenna, measures the subaqueous profile at high tide. The dolly is used to help ensure data is collected along a continuous profile, through water that is too deep for ATV, and where there is too much turbidity for the jet ski sonar. The receivers on the vehicles transitioned from Sokkia, to Ashtech ZXtreme, and are now equipped with Trimble NetR9 GNSS receivers (enabling access to multiple Global Navigation Satellite Systems). The GNSS sample rates have increased over time, and data are now collected at 5Hz. Base stations broadcast real-time kinematic corrections that allow jet ski and ATV drivers to monitor the data quality, follow designated transect lines, and guide dolly pushers, using custom in-house software. Vehicles are driven at a speed that samples ~1 point per meter of track. Data are routinely post-processed. SBG Ellipse inertial measurement units on the jet ski and ATV account for tilting of the antenna. Prior to the advent of MEMS, a KVH Gyrocompass was used. The ATV driver also manually records subaerial substrate type with a switch that differentiates between rock, cobble and sand. The location, spacing, and orientation of full survey transects evolved organically over time and space. At Torrey Pines, surveying began before the creation of the MOP model, and cross-shore transects were orthogonal to the approximate orientation of the MHHW contour over a few km alongshore. Subaerial ATV-only surveys are driven alongshore with approximately 10m cross-shore spacing. Nominally, full surveys are quarterly and subaerial surveys are monthly. Quality controlled elevation data (NAVD88 GEOID99 epoch 2002) are provided for each survey at both Lat-Lon (NAD83 CORS96, epoch 2002, ellipsoid GRS80) and UTM (Zone 11) coordinates. When available, subaerial substrate type (sand, rock or cobble) is also provided. Errors in survey elevation are variable in space and time, and depend on GNSS-platform, bed smoothness, and wave and ocean temperature stratification conditions. Root-mean-square-errors are usually less than 15cm with the jet ski, and a few cm smaller with the dolly and ATV. Be cautious with data at depths greater than 8m below MSL, as ocean temperature stratification can contaminate jet ski soundings. Gaps in spatial coverage occurred when low and high tide surveys did not overlap, owing to the nonlinear interaction of sand bars, waves, tides, kelp, permits, and mechanical failures. Pre- and post- survey control points were used for accuracy verification on each survey. The Online Positioning User Service (OPUS) was used to determine base locations and survey control locations. Inertial measurement units were calibrated on the vehicles and tested. Realtime ocean surface water temperature was recorded during the jet ski surveys to correct for the sonar travel time measurements. Jet ski, dolly, and ATV data are collected over the same transect line with overlap for redundancy and as a check on data quality. Vertical discrepancies are flagged and outliers are removed. The sonar and IMU are oversampled to improve noise rejection. ATV tire pressure is held at 5 PSI and verified prior to each survey. Various jet ski parameters were set at thresholds that maintained high quality (e.g. 30 degree max pitch/roll, maximum Position of Dilution of Precision of 5.0). Raw (quality controlled) sand level data provide maximum user flexibility. Binned and mapped data are more user-convenient for many applications, but sharp edges are blurred. Raw data should be used to examine vertical scarps at the seaward face of nourishments, and steep reef and canyon bathymetry. Be cautious with data at depths greater than 8m below MSL, as ocean temperature stratification can contaminate jet ski soundings. Complete lists of all survey filenames, dates, depth zones surveyed, alongshore regions surveyed, south and north-most surveyed MOP line indices with good coverage, regions influenced by nourishment, and vehicles and transects driven are included in the torrey_survey_info.nc file (separate download).

Binned sand elevations at Torrey Pines Beach. Raw sand level observations are binned to coordinates aligned with the wave estimates (MOP lines). MOP lines are separated 100m alongshore, and oriented from the 10m depth contour to the backbeach, to approximately follow the curving coastline. Bins centered on MOP lines with 5m cross-shore resolution are filled with median values, suppressing the effect of outliers. All surveys are binned, including surveys with transects not originally aligned to MOP lines and with alongshore spacing less than 100m. The observations are usually smooth over the 50m maximum distance of alongshore projection and 2.5m cross-shore projection. However, raw data should be used to define features with shorter scales (i.e., scarps, reef, canyon). Binned alongshore resolution can be adjusted in the repository code (separate download: analysis_code within analysis folder) by using different binning transects, while cross-shore resolution can be adjusted by redefining the "cres" variable. Be cautious with data at depths greater than 8m below MSL, as ocean temperature stratification can contaminate jet ski soundings.

Mapped sand elevations at Torrey Pines Beach. Elevation maps are created on the same grid as the binned observations, but are smoothed and fill in small data gaps. For each survey, bins containing less than 3 data points are considered unsampled and are discarded. Map boundaries are defined as grid points that are regularly sampled during unnourished quarterly full surveys (must be populated at least 25\% of the time as the most frequently full surveyed grid point, during times without nourishment). Grid points with an unnourished average depth greater than 8m are not mapped because speed of sound errors due to stratification may contaminate jet ski sonar measurements. When the estimated interpolation (or extrapolation) error is large (NMSE>0.2), the map bin elevation is considered missing and filled with the value -99999.

Information on sand level surveys conducted at Torrey Pines Beach. Complete lists of all survey filenames, dates, depth zones surveyed, alongshore regions surveyed, south and north-most surveyed MOP line indices with good coverage, regions influenced by nourishment, and vehicles and transects driven are included in this file.

Characteristics of Torrey Pines Beach. MOP DEFINITIONS: The beach site locations are defined using MOP lines. Backbeach locations of each line (spaced 100m apart in the alongshore) and the corresponding offshore locations in 10m depth are included, as well as the MOP site names, index number, and the angle of the line relative to true north. REGIONS: The monitoring schemes at each beach evolved over time with consistently surveyed regions spanning between 1.6 and 2.7km alongshore. Region outlines, and MOP site names and index numbers within each region are provided, as well as times with minimal nourishment influence. SECTIONS: Beaches were split into sections spanning 700-900m alongshore. Location outlines, MOP sites and index numbers, and times of minimal nourishment influence are provided for each section. Additionally, features (e.g. reef, lagoon, canyon) are listed. The sections that are labeled as 1D, have a coherent seasonal cross-shore sand exchange signal along the profile, as identified with empirical orthogonal function analysis. During times of minimal nourishment influence, these 1D sections are recommended for testing 1-D cross-shore beach profile evolution models. Note that cobble may be present even in 1D sections, especially at North Torrey Pines when subaerial sand levels are eroded. NOURISHMENT: Sand nourishment placement locations and start and end times are provided. The nourishment placement outline is defined as the bulge in the 2m contour (relative to MSL) location between the pre and post-nourishment surveys. HARD SUBSTRATE: Subaerial substrate is monitored by the ATV driver, however, offshore substrate is difficult to identify. Areas with underlying hard substrate erode to minimum levels significantly less than adjacent sandy areas. Specifically, these areas are defined as areas with mapped minimum surface greater than 30cm relative to the time- and alongshore-averaged mapped profile in the alongshore uniform sections. These locations agree qualitatively with limited available sidescan sonar which helped to identify the hard substrate as rocky reef. VOLUMES: For each survey, maps are used to estimate sand volumes relative to the minimum surface. The minimum value in each mapped grid point over the study period is used to calculate the minimum surface. The total volume is estimated over the survey area, while subaerial volume is calculated over an area which extends from the mean shoreline position (average location of the intersection of the profile with MSL) to the backbeach. Estimates are provided for each beach, region and section. Volume estimates are discarded if more than 10% of the mapped area has NMSE>0.2. BEACH WIDTHS: Beach width is calculated along each MOP line as the positive slope intersection of the MSL contour with the mapped profile where NMSE< 0.2. If more than one intersection is found, the most offshore MSL position is used, as long as no negative slope intersection is seaward of it. Alongshore-averaged beach widths are provided for each beach, region and section when less than 10% of MOP lines were missing estimates.

Raw (quality controlled) sand elevations at Cardiff and Solana Beaches. An ATV with rear shocks removed and constant tire pressure (to maintain a consistent distance from the GNSS antenna to the sand level below), was used to measure the subaerial beach at low tide, while a 3 wheeled push dolly (with GNSS antenna mounted on a fixed-height mast) was used from the low-tide waterline to chest deep wading depths. A personal watercraft (Yamaha Waverunner, but here the more familiar term jet ski will be used) equipped with 192kHz acoustic sonar, sea surface thermistor (for speed of sound calculation) and GNSS antenna, measures the subaqueous profile at high tide. The dolly is used to help ensure data is collected along a continuous profile, through water that is too deep for ATV, and where there is too much turbidity for the jet ski sonar. The receivers on the vehicles transitioned from Sokkia, to Ashtech ZXtreme, and are now equipped with Trimble NetR9 GNSS receivers (enabling access to multiple Global Navigation Satellite Systems). The GNSS sample rates have increased over time, and data are now collected at 5Hz. Base stations broadcast real-time kinematic corrections that allow jet ski and ATV drivers to monitor the data quality, follow designated transect lines, and guide dolly pushers, using custom in-house software. Vehicles are driven at a speed that samples ~1 point per meter of track. Data are routinely post-processed. SBG Ellipse inertial measurement units on the jet ski and ATV account for tilting of the antenna. Prior to the advent of MEMS, a KVH Gyrocompass was used. The ATV driver also manually records subaerial substrate type with a switch that differentiates between rock, cobble and sand. The location, spacing, and orientation of full survey transects evolved organically over time and space. At Cardiff, surveying began before the creation of the MOP model, and cross-shore transects were orthogonal to the approximate orientation of the MHHW contour over a few km alongshore. Cardiff and Solana transects aligned with MOP transects starting November 23, 2011. Subaerial ATV-only surveys are driven alongshore with approximately 10m cross-shore spacing. Nominally, full surveys are quarterly and subaerial surveys are monthly. Quality controlled elevation data (NAVD88 GEOID99 epoch 2002) are provided for each survey at both Lat-Lon (NAD83 CORS96, epoch 2002, ellipsoid GRS80) and UTM (Zone 11) coordinates. When available, subaerial substrate type (sand, rock or cobble) is also provided. Errors in survey elevation are variable in space and time, and depend on GNSS-platform, bed smoothness, and wave and ocean temperature stratification conditions. Root-mean-square-errors are usually less than 15cm with the jet ski, and a few cm smaller with the dolly and ATV. Be cautious with data at depths greater than 8m below MSL, as ocean temperature stratification can contaminate jet ski soundings. Gaps in spatial coverage occurred when low and high tide surveys did not overlap, owing to the nonlinear interaction of sand bars, waves, tides, kelp, permits, and mechanical failures. Pre- and post- survey control points were used for accuracy verification on each survey. The Online Positioning User Service (OPUS) was used to determine base locations and survey control locations. Inertial measurement units were calibrated on the vehicles and tested. Realtime ocean surface water temperature was recorded during the jet ski surveys to correct for the sonar travel time measurements. Jet ski, dolly, and ATV data are collected over the same transect line with overlap for redundancy and as a check on data quality. Vertical discrepancies are flagged and outliers are removed. The sonar and IMU are oversampled to improve noise rejection. ATV tire pressure is held at 5 PSI and verified prior to each survey. Various jet ski parameters were set at thresholds that maintained high quality (e.g. 30 degree max pitch/roll, maximum Position of Dilution of Precision of 5.0). Raw (quality controlled) sand level data provide maximum user flexibility. Binned and mapped data are more user-convenient for many applications, but sharp edges are blurred. Raw data should be used to examine vertical scarps at the seaward face of nourishments, and steep reef or cobble piles. Be cautious with data at depths greater than 8m below MSL, as ocean temperature stratification can contaminate jet ski soundings. Complete lists of all survey filenames, dates, depth zones surveyed, alongshore regions surveyed, south and north-most surveyed MOP line indices with good coverage, regions influenced by nourishment, and vehicles and transects driven are included in the cardiff-solana_survey_info.nc file (separate download).

Binned sand elevations at Cardiff and Solana Beaches. Raw sand level observations are binned to coordinates aligned with the wave estimates (MOP lines). MOP lines are separated 100m alongshore, and oriented from the 10m depth contour to the backbeach, to approximately follow the curving coastline. Bins centered on MOP lines with 5m cross-shore resolution are filled with median values, suppressing the effect of outliers. All surveys are binned, including surveys with transects not originally aligned to MOP lines and with alongshore spacing less than 100m. The observations are usually smooth over the 50m maximum distance of alongshore projection and 2.5m cross-shore projection. However, raw data should be used to define features with shorter scales (i.e., scarps, reef). Binned alongshore resolution can be adjusted in the repository code (separate download: analysis_code within analysis folder) by using different binning transects, while cross-shore resolution can be adjusted by redefining the "cres" variable. Be cautious with data at depths greater than 8m below MSL, as ocean temperature stratification can contaminate jet ski soundings.

Mapped sand elevations at Cardiff and Solana Beaches. Elevation maps are created on the same grid as the binned observations, but are smoothed and fill in small data gaps. For each survey, bins containing less than 3 data points are considered unsampled and are discarded. Map boundaries are defined as grid points that are regularly sampled during unnourished quarterly full surveys (must be populated at least 25\% of the time as the most frequently full surveyed grid point, during times without nourishment). Grid points with an unnourished average depth greater than 8m are not mapped because speed of sound errors due to stratification may contaminate jet ski sonar measurements. When the estimated interpolation (or extrapolation) error is large (NMSE>0.2), the map bin elevation is considered missing and filled with the value -99999.

Information on sand level surveys conducted at Cardiff and Solana Beaches. Complete lists of all survey filenames, dates, depth zones surveyed, alongshore regions surveyed, south and north-most surveyed MOP line indices with good coverage, regions influenced by nourishment, and vehicles and transects driven are included in this file.

Characteristics of Cardiff and Solana Beaches. MOP DEFINITIONS: The beach site locations are defined using MOP lines. Backbeach locations of each line (spaced 100m apart in the alongshore) and the corresponding offshore locations in 10m depth are included, as well as the MOP site names, index number, and the angle of the line relative to true north. REGIONS: The monitoring schemes at each beach evolved over time with consistently surveyed regions spanning between 1.6 and 2.7km alongshore. Region outlines, and MOP site names and index numbers within each region are provided, as well as times with minimal nourishment influence. SECTIONS: Beaches were split into sections spanning 700-900m alongshore. Location outlines, MOP sites and index numbers, and times of minimal nourishment influence are provided for each section. Additionally, features (e.g. reef) are listed. The sections that are labeled as 1D, have a coherent seasonal cross-shore sand exchange signal along the profile, as identified with empirical orthogonal function analysis. During times of minimal nourishment influence, these 1D sections are recommended for testing 1-D cross-shore beach profile evolution models. Note that cobble may be present even in 1D sections, especially at Cardiff when subaerial sand levels are eroded. NOURISHMENT: Sand nourishment placement locations and start and end times are provided. The nourishment placement outline is defined as the bulge in the 2m contour (relative to MSL) location between the pre and post-nourishment surveys. HARD SUBSTRATE: Subaerial substrate is monitored by the ATV driver, however, offshore substrate is difficult to identify. Areas with underlying hard substrate erode to minimum levels significantly less than adjacent sandy areas. Specifically, these areas are defined as areas with mapped minimum surface greater than 30cm relative to the time- and alongshore-averaged mapped profile in the alongshore uniform sections. These locations agree qualitatively with limited available sidescan sonar which helped to identify the hard substrate as rocky reef. VOLUMES: For each survey, maps are used to estimate sand volumes relative to the minimum surface. The minimum value in each mapped grid point over the study period is used to calculate the minimum surface. The total volume is estimated over the survey area, while subaerial volume is calculated over an area which extends from the mean shoreline position (average location of the intersection of the profile with MSL) to the backbeach. Estimates are provided for each beach, region and section. Volume estimates are discarded if more than 10% of the mapped area has NMSE>0.2. BEACH WIDTHS: Beach width is calculated along each MOP line as the positive slope intersection of the MSL contour with the mapped profile where NMSE< 0.2. If more than one intersection is found, the most offshore MSL position is used, as long as no negative slope intersection is seaward of it. Alongshore-averaged beach widths are provided for each beach, region and section when less than 10% of MOP lines were missing estimates.

Raw (quality controlled) sand elevations at Imperial Beach. An ATV with rear shocks removed and constant tire pressure (to maintain a consistent distance from the GNSS antenna to the sand level below), was used to measure the subaerial beach at low tide, while a 3 wheeled push dolly (with GNSS antenna mounted on a fixed-height mast) was used from the low-tide waterline to chest deep wading depths. A personal watercraft (Yamaha Waverunner, but here the more familiar term jet ski will be used) equipped with 192kHz acoustic sonar, sea surface thermistor (for speed of sound calculation) and GNSS antenna, measures the subaqueous profile at high tide. The dolly is used to help ensure data is collected along a continuous profile, through water that is too deep for ATV, and where there is too much turbidity for the jet ski sonar. The receivers on the vehicles transitioned from Sokkia, to Ashtech ZXtreme, and are now equipped with Trimble NetR9 GNSS receivers (enabling access to multiple Global Navigation Satellite Systems). The GNSS sample rates have increased over time, and data are now collected at 5Hz. Base stations broadcast real-time kinematic corrections that allow jet ski and ATV drivers to monitor the data quality, follow designated transect lines, and guide dolly pushers, using custom in-house software. Vehicles are driven at a speed that samples ~1 point per meter of track. Data are routinely post-processed. SBG Ellipse inertial measurement units on the jet ski and ATV account for tilting of the antenna. Prior to the advent of MEMS, a KVH Gyrocompass was used. The ATV driver also manually records subaerial substrate type with a switch that differentiates between rock, cobble and sand. Full survey cross-shore transects are aligned to MOP lines with 100m alongshore spacing. Subaerial ATV-only surveys are driven alongshore with approximately 10m cross-shore spacing. Nominally, full surveys are quarterly and subaerial surveys are monthly. Quality controlled elevation data (NAVD88 GEOID99 epoch 2002) are provided for each survey at both Lat-Lon (NAD83 CORS96, epoch 2002, ellipsoid GRS80) and UTM (Zone 11) coordinates. When available, subaerial substrate type (sand, rock or cobble) is also provided. Errors in survey elevation are variable in space and time, and depend on GNSS-platform, bed smoothness, and wave and ocean temperature stratification conditions. Root-mean-square-errors are usually less than 15cm with the jet ski, and a few cm smaller with the dolly and ATV. Be cautious with data at depths greater than 8m below MSL, as ocean temperature stratification can contaminate jet ski soundings. Gaps in spatial coverage occurred when low and high tide surveys did not overlap, owing to the nonlinear interaction of sand bars, waves, tides, kelp, permits, and mechanical failures. Pre- and post- survey control points were used for accuracy verification on each survey. The Online Positioning User Service (OPUS) was used to determine base locations and survey control locations. Inertial measurement units were calibrated on the vehicles and tested. Realtime ocean surface water temperature was recorded during the jet ski surveys to correct for the sonar travel time measurements. Jet ski, dolly, and ATV data are collected over the same transect line with overlap for redundancy and as a check on data quality. Vertical discrepancies are flagged and outliers are removed. The sonar and IMU are oversampled to improve noise rejection. ATV tire pressure is held at 5 PSI and verified prior to each survey. Various jet ski parameters were set at thresholds that maintained high quality (e.g. 30 degree max pitch/roll, maximum Position of Dilution of Precision of 5.0). Raw (quality controlled) sand level data provide maximum user flexibility. Binned and mapped data are more user-convenient for many applications, but sharp edges are blurred. Raw data should be used to examine vertical scarps at the seaward face of nourishments, and steep shoal bathymetry. Be cautious with data at depths greater than 8m below MSL, as ocean temperature stratification can contaminate jet ski soundings. Complete lists of all survey filenames, dates, depth zones surveyed, alongshore regions surveyed, south and north-most surveyed MOP line indices with good coverage, regions influenced by nourishment, and vehicles and transects driven are included in the imperial_survey_info.nc file (separate download).

Binned sand elevations at Imperial Beach. Raw sand level observations are binned to coordinates aligned with the wave estimates (MOP lines). MOP lines are separated 100m alongshore, and oriented from the 10m depth contour to the backbeach, to approximately follow the curving coastline. Bins centered on MOP lines with 5m cross-shore resolution are filled with median values, suppressing the effect of outliers. The observations are usually smooth over the 50m maximum distance of alongshore projection and 2.5m cross-shore projection. However, raw data should be used to define features with shorter scales (i.e., scarps). Binned alongshore resolution can be adjusted in the repository code (separate download: analysis_code within analysis folder) by using different binning transects, while cross-shore resolution can be adjusted by redefining the "cres" variable. Be cautious with data at depths greater than 8m below MSL, as ocean temperature stratification can contaminate jet ski soundings.

Mapped sand elevations at Imperial Beach. Elevation maps are created on the same grid as the binned observations, but are smoothed and fill in small data gaps. For each survey, bins containing less than 3 data points are considered unsampled and are discarded. Map boundaries are defined as grid points that are regularly sampled during unnourished quarterly full surveys (must be populated at least 25\% of the time as the most frequently full surveyed grid point, during times without nourishment). Grid points with an unnourished average depth greater than 8m are not mapped because speed of sound errors due to stratification may contaminate jet ski sonar measurements. When the estimated interpolation (or extrapolation) error is large (NMSE>0.2), the map bin elevation is considered missing and filled with the value -99999.

Information on sand level surveys conducted at Imperial Beach. Complete lists of all survey filenames, dates, depth zones surveyed, alongshore regions surveyed, south and north-most surveyed MOP line indices with good coverage, regions influenced by nourishment, and vehicles and transects driven are included in this file.

Characteristics of Imperial Beach. MOP DEFINITIONS: The beach site locations are defined using MOP lines. Backbeach locations of each line (spaced 100m apart in the alongshore) and the corresponding offshore locations in 10m depth are included, as well as the MOP site names, index number, and the angle of the line relative to true north. REGIONS: The monitoring schemes at each beach evolved over time with consistently surveyed regions spanning between 1.6 and 2.7km alongshore. Region outlines, and MOP site names and index numbers within each region are provided, as well as times with minimal nourishment influence. SECTIONS: Beaches were split into sections spanning 700-900m alongshore. Location outlines, MOP sites and index numbers, and times of minimal nourishment influence are provided for each section. Additionally, features (e.g. pier, jetty, shoal) are listed. The sections that are labeled as 1D, have a coherent seasonal cross-shore sand exchange signal along the profile, as identified with empirical orthogonal function analysis. During times of minimal nourishment influence, these 1D sections are recommended for testing 1-D cross-shore beach profile evolution models. Note that cobble may be present even in 1D sections, especially when subaerial sand levels are eroded. PIER AND JETTY LOCATIONS: The locations of the pier and two short jetties are included. NOURISHMENT: Sand nourishment placement locations and start and end times are provided. The nourishment placement outline is defined as the bulge in the 2m contour (relative to MSL) location between the pre and post-nourishment surveys. HARD SUBSTRATE: Subaerial substrate is monitored by the ATV driver, however, offshore substrate is difficult to identify. Areas with underlying hard substrate erode to minimum levels significantly less than adjacent sandy areas. Specifically, these areas are defined as areas with mapped minimum surface greater than 30cm relative to the time- and alongshore-averaged mapped profile in the alongshore uniform sections. These locations agree qualitatively with limited available sidescan sonar which helped to identify the hard substrate as cobble shoal. VOLUMES: For each survey, maps are used to estimate sand volumes relative to the minimum surface. The minimum value in each mapped grid point over the study period is used to calculate the minimum surface. The total volume is estimated over the survey area, while subaerial volume is calculated over an area which extends from the mean shoreline position (average location of the intersection of the profile with MSL) to the backbeach. Estimates are provided for each beach, region and section. Volume estimates are discarded if more than 10% of the mapped area has NMSE>0.2. BEACH WIDTHS: Beach width is calculated along each MOP line as the positive slope intersection of the MSL contour with the mapped profile where NMSE< 0.2. If more than one intersection is found, the most offshore MSL position is used, as long as no negative slope intersection is seaward of it. Alongshore-averaged beach widths are provided for each beach, region and section when less than 10% of MOP lines were missing estimates.

All code and files used in processing and figure creation are included in this folder. All data files created and used in processing are formatted in the Network Common Data Form (NetCDF) and can be read using MATLAB, Python, Fortran, C, C++, Java, and other languages. Code is written in MATLAB (R2018b). Although MATLAB is a proprietary language, the .m files can be read with a text viewer.