Analysis of Tidal Scour Rates

Bathymetric Time Series Analysis of Tidal Scour Rates in Elkhorn Slough 1993- 2009 MAPPING APLOOR Direen, R., Frame, J., Galvan, J., Gonzalez, G., Hall, A., Hosler, C., Jones, A., Sandersfeld, M., Stoner, K. , Wrubel, K. Undergraduate Class Project ENVS 433 Applied Coastal Remote Sensing - California State University, Monterey Bay 100 Campus Center, Seaside, CA 93955 USA Introduction Jone& Cross-section 1993-2009 Over the past 100 years S0% of California's wetlands have been destrayed (Buchsbaum 2000). Wetlands are ecologically important ecosystems that provide a wide array of services that we take advantage of on a daily basis. In California, urban spread and agriculture have caused the vast majority of aur wetlands to disappear. Elkhorn Slough, one of the last remaining coastal wetlands In California, has been experiencing rapid habitat loss since the opening af the Moss Landing Harber mouth in 1946, which increased tidal flux from seasonal to daily. Previous studies have dacumented rapid and accelerating rates of tidal flow, erosion and habitat loss along the main channel, and a variety of management actions are now b Estuarine Research Reserve (ESNERR) (Broenkow and Breaker 2005 and Bildstein et, al. 2001). Malzone (1999) compared bathymetric data from 1988 ta 1993, which indicated a sediment lass of Sx104 m3/yr. Two fallaw up studies, conducted by Sampey (2005) and Dean (2003] concluded that between 2001 and 2003 the Slough continued to erode at 1.5 times the annual rate cakulated by Malzone. being considered by the Elkhorn Slough National erosion accurring in the seaf these studies documented an overall deepening of the central channel with the hiest rates of Dimit d half of the slaugh west af the Parsans Slough mauth (zanes 1-4), with significant but lower rates faund in the mid slough (zanes 5-6) and low to no erosion accurring towards the head (zones 7-8). ESNERR initiated the Elkharn Slough Tidal Wetlands Project (ESTWP) to recommend management solutions to halt or reverse these processes (Caffrey et. al. 2002). The goal af the present study is to determine whether the spatial pattem and rates of tidal scour and erosion have changed since the 200a survey Zane? Cros-sectios 19-0s A time series analysis was continued along the thalweg to determine if the rate of change in Elkhom Slough is increasing decreasing, ar reaching an equilibrium state. Using bathymetric data callected in 1993, 2001, 2003, 2005, and 2009, crass-sections were compared in the eight zones of the slough to test the following hypotheses: H1: Between 1993 and 2009, the erosion rate has increased. H2: Between 1993 and 2009, the erosion rate has slowed. Methods Assessing the rate of change within Elkharn Slough required a continuation of the time series analysis. The Seafloor Mapping Laboratory at California State University Monterey Bay (CSUMB) conducted a high resolution bathymetry and topographic survey of Elkhorn Slough using a Swathplus 200khz interferometric sidescan sonar and vessel-based Riegl i420LM terrestrial LIDAR system. HYPACK hydrographic package provided survey planning and navigation. Data from an Applanix POSMV v4 was used for positioning, attitude and tidal correction after differential correction and processing in POSPAC 5 software. Sound velocity data was collected using an SV+ profiler. Sonar and LIDAR data were exported as asci files in UTM coardinates NAD83 (CORS96) HAE and converted to NAVDSS Geaid03 using Corpscon 6. Soundings files were then converted to PFM format for CUBE cleaning in IVS Fledermaus where erroneous points were removed both manually and with filters. Cleaned soundings were exported as comma separated text files from a one meter CUBE surface, and used to create a combined bathymetric/topographic 1m DEM using ArcMap 9.2 (ESRI, 2006) covering the length of the slough. Raster subtraction was used to quantify changes in bathymetry from 2005 to 2009. Spatial changes in channel depth between 1993 and 2009 were examined using longitudinal profiles of the thalweg. Multi-year cross- sectional profile comparisons were created for each of the eight erosion zanes along the length of the Slough identified in previous studies. These profiles were used to evaluate and contrast patterns of change in widths and depths of the main channel and intertidal mudflats. Annual Erosion Rates 2005-2009 bathymetric change meterslyear -1.0- 05 0.5-04 0.4.03 03-02 Results & Conclusions 42-01 4.1-05 Overal, the Ekhorn Slough is stil daminated by erosion, but at a rate that appears to be slowing (back ground image of 2005-2009 raster subtraction resuks in annualined bathymetric change, with warm colors indicating ermion and cool colors showing deponiton - see legend for scale. Values of +-0.05m/y are below the precision of the data and have been excluded from the analysis and display). Resuks from serial pair wise raster subtractions and the profile analyses shown in example cross section graphs for each erosion zone here and desrribed below indicate that while there is still a head to mouth gradient of increasing ermsion along the thalweg. particubrty west of Parsons Slough (zones 1-41, the rates are now diminishing from what they were in past years. Moreover, through the novel application of mobile marine topagraphic LIDAR there is compeling evidence of signiřicant sediment deposition on the mudlats. 0.05 -0 0.06 -0.1 0.1-0.2 ZONE 1- Dramatic deepening > 2m) and widening (20m) from 1993 to 2001, with continued down cutting from 2008 to 2005 at a slower rate, and no further down cutting occurred after 2005. There is some evidence of the main channel wldening after 2005, and the mudtlats continuing to shoal since 2001 (05m) after first eroding between 1993 and 2001 ( 0Sm) ZONE 2- Dramatic down outting ( 2m) and widening (30m) of main channel from 1993 to 2005 with change over the next four years to 2009 Continued deposition im) on mudlats of narthern share after initial erosion between 1993 and 2001 (OSm). ZONE 3- Dramatic de E4.Pacnor epening la 2m) and widening of the cross sectional area from 1993 to 2005 with Ittle change between 2005 and 2009. 02-0.3 03-0.4 04 -0.5 a5-1 Slough mouth has erpariencad the h e hiahest erosion rates recorded in the siouah, with the areatast chanze accuming from 1993 to 2001 (> 2.5m), and continued down cutting through 2003 and another increase in erosion rates from 2005 to 2009 (0.5m). ZONE S - Very ittle change along manit of the thalwng over the years, but some dawn cutting 0 75m) and widening (10m) from 1993 to 2005 in creis section fallowed by Iittle change through 2009. Possible deposition (c0.25m) within the main channel has occurred from 2003 to 2009, but this relatively small change may be below the precision of our analysis. The mudnats have shoaled between 1993 and 2000. ZONE G-St less change in this zone along the thalweg from 1993 to 2009 (< 0.Sm), Little change from 1993 to 2001, wth the only jump in down cutting in the main channel from 2001 to 2003, followed by no apparent change in the main channel cross section from 2003 to 2009. The mudfians, however, have received measurable depostion (05m) ZONE 7-No detectable change along the thalweg apart from some channel migration and minor widening at bends. Measurable depostion has occurred on the mudflats (up to 0.5m). ZONE 8 - There appears to have been some minor down cutting ( O.5m) in the main channel between 1993 and 2003, followed by deposition in both the main channel and on the mud flats through 2009 Elkhorn Slough Thalweg 1993-2009 zone 1 zone 2 zone 3 zone 5 zone 8 zone 7 Zone4 Cross section 1993-2009 Zons 1 Cross-sectian 1953-2000 Jane 2Oren seoloe Zene 4 Parnora Sleugh Thahwag1903-20m Bathymetric Time Series Analysis of Tidal Scour Rates in Elkhorn Slough 1993- 2009 MAPPING APLOOR Direen, R., Frame, J., Galvan, J., Gonzalez, G., Hall, A., Hosler, C., Jones, A., Sandersfeld, M., Stoner, K. , Wrubel, K. Undergraduate Class Project ENVS 433 Applied Coastal Remote Sensing - California State University, Monterey Bay 100 Campus Center, Seaside, CA 93955 USA Introduction Jone& Cross-section 1993-2009 Over the past 100 years S0% of California's wetlands have been destrayed (Buchsbaum 2000). Wetlands are ecologically important ecosystems that provide a wide array of services that we take advantage of on a daily basis. In California, urban spread and agriculture have caused the vast majority of aur wetlands to disappear. Elkhorn Slough, one of the last remaining coastal wetlands In California, has been experiencing rapid habitat loss since the opening af the Moss Landing Harber mouth in 1946, which increased tidal flux from seasonal to daily. Previous studies have dacumented rapid and accelerating rates of tidal flow, erosion and habitat loss along the main channel, and a variety of management actions are now b Estuarine Research Reserve (ESNERR) (Broenkow and Breaker 2005 and Bildstein et, al. 2001). Malzone (1999) compared bathymetric data from 1988 ta 1993, which indicated a sediment lass of Sx104 m3/yr. Two fallaw up studies, conducted by Sampey (2005) and Dean (2003] concluded that between 2001 and 2003 the Slough continued to erode at 1.5 times the annual rate cakulated by Malzone. being considered by the Elkhorn Slough National erosion accurring in the seaf these studies documented an overall deepening of the central channel with the hiest rates of Dimit d half of the slaugh west af the Parsans Slough mauth (zanes 1-4), with significant but lower rates faund in the mid slough (zanes 5-6) and low to no erosion accurring towards the head (zones 7-8). ESNERR initiated the Elkharn Slough Tidal Wetlands Project (ESTWP) to recommend management solutions to halt or reverse these processes (Caffrey et. al. 2002). The goal af the present study is to determine whether the spatial pattem and rates of tidal scour and erosion have changed since the 200a survey Zane? Cros-sectios 19-0s A time series analysis was continued along the thalweg to determine if the rate of change in Elkhom Slough is increasing decreasing, ar reaching an equilibrium state. Using bathymetric data callected in 1993, 2001, 2003, 2005, and 2009, crass-sections were compared in the eight zones of the slough to test the following hypotheses: H1: Between 1993 and 2009, the erosion rate has increased. H2: Between 1993 and 2009, the erosion rate has slowed. Methods Assessing the rate of change within Elkharn Slough required a continuation of the time series analysis. The Seafloor Mapping Laboratory at California State University Monterey Bay (CSUMB) conducted a high resolution bathymetry and topographic survey of Elkhorn Slough using a Swathplus 200khz interferometric sidescan sonar and vessel-based Riegl i420LM terrestrial LIDAR system. HYPACK hydrographic package provided survey planning and navigation. Data from an Applanix POSMV v4 was used for positioning, attitude and tidal correction after differential correction and processing in POSPAC 5 software. Sound velocity data was collected using an SV+ profiler. Sonar and LIDAR data were exported as asci files in UTM coardinates NAD83 (CORS96) HAE and converted to NAVDSS Geaid03 using Corpscon 6. Soundings files were then converted to PFM format for CUBE cleaning in IVS Fledermaus where erroneous points were removed both manually and with filters. Cleaned soundings were exported as comma separated text files from a one meter CUBE surface, and used to create a combined bathymetric/topographic 1m DEM using ArcMap 9.2 (ESRI, 2006) covering the length of the slough. Raster subtraction was used to quantify changes in bathymetry from 2005 to 2009. Spatial changes in channel depth between 1993 and 2009 were examined using longitudinal profiles of the thalweg. Multi-year cross- sectional profile comparisons were created for each of the eight erosion zanes along the length of the Slough identified in previous studies. These profiles were used to evaluate and contrast patterns of change in widths and depths of the main channel and intertidal mudflats. Annual Erosion Rates 2005-2009 bathymetric change meterslyear -1.0- 05 0.5-04 0.4.03 03-02 Results & Conclusions 42-01 4.1-05 Overal, the Ekhorn Slough is stil daminated by erosion, but at a rate that appears to be slowing (back ground image of 2005-2009 raster subtraction resuks in annualined bathymetric change, with warm colors indicating ermion and cool colors showing deponiton - see legend for scale. Values of +-0.05m/y are below the precision of the data and have been excluded from the analysis and display). Resuks from serial pair wise raster subtractions and the profile analyses shown in example cross section graphs for each erosion zone here and desrribed below indicate that while there is still a head to mouth gradient of increasing ermsion along the thalweg. particubrty west of Parsons Slough (zones 1-41, the rates are now diminishing from what they were in past years. Moreover, through the novel application of mobile marine topagraphic LIDAR there is compeling evidence of signiřicant sediment deposition on the mudlats. 0.05 -0 0.06 -0.1 0.1-0.2 ZONE 1- Dramatic deepening > 2m) and widening (20m) from 1993 to 2001, with continued down cutting from 2008 to 2005 at a slower rate, and no further down cutting occurred after 2005. There is some evidence of the main channel wldening after 2005, and the mudtlats continuing to shoal since 2001 (05m) after first eroding between 1993 and 2001 ( 0Sm) ZONE 2- Dramatic down outting ( 2m) and widening (30m) of main channel from 1993 to 2005 with change over the next four years to 2009 Continued deposition im) on mudlats of narthern share after initial erosion between 1993 and 2001 (OSm). ZONE 3- Dramatic de E4.Pacnor epening la 2m) and widening of the cross sectional area from 1993 to 2005 with Ittle change between 2005 and 2009. 02-0.3 03-0.4 04 -0.5 a5-1 Slough mouth has erpariencad the h e hiahest erosion rates recorded in the siouah, with the areatast chanze accuming from 1993 to 2001 (> 2.5m), and continued down cutting through 2003 and another increase in erosion rates from 2005 to 2009 (0.5m). ZONE S - Very ittle change along manit of the thalwng over the years, but some dawn cutting 0 75m) and widening (10m) from 1993 to 2005 in creis section fallowed by Iittle change through 2009. Possible deposition (c0.25m) within the main channel has occurred from 2003 to 2009, but this relatively small change may be below the precision of our analysis. The mudnats have shoaled between 1993 and 2000. ZONE G-St less change in this zone along the thalweg from 1993 to 2009 (< 0.Sm), Little change from 1993 to 2001, wth the only jump in down cutting in the main channel from 2001 to 2003, followed by no apparent change in the main channel cross section from 2003 to 2009. The mudfians, however, have received measurable depostion (05m) ZONE 7-No detectable change along the thalweg apart from some channel migration and minor widening at bends. Measurable depostion has occurred on the mudflats (up to 0.5m). ZONE 8 - There appears to have been some minor down cutting ( O.5m) in the main channel between 1993 and 2003, followed by deposition in both the main channel and on the mud flats through 2009 Elkhorn Slough Thalweg 1993-2009 zone 1 zone 2 zone 3 zone 5 zone 8 zone 7 Zone4 Cross section 1993-2009 Zons 1 Cross-sectian 1953-2000 Jane 2Oren seoloe Zene 4 Parnora Sleugh Thahwag1903-20m Bathymetric Time Series Analysis of Tidal Scour Rates in Elkhorn Slough 1993- 2009 MAPPING APLOOR Direen, R., Frame, J., Galvan, J., Gonzalez, G., Hall, A., Hosler, C., Jones, A., Sandersfeld, M., Stoner, K. , Wrubel, K. Undergraduate Class Project ENVS 433 Applied Coastal Remote Sensing - California State University, Monterey Bay 100 Campus Center, Seaside, CA 93955 USA Introduction Jone& Cross-section 1993-2009 Over the past 100 years S0% of California's wetlands have been destrayed (Buchsbaum 2000). Wetlands are ecologically important ecosystems that provide a wide array of services that we take advantage of on a daily basis. In California, urban spread and agriculture have caused the vast majority of aur wetlands to disappear. Elkhorn Slough, one of the last remaining coastal wetlands In California, has been experiencing rapid habitat loss since the opening af the Moss Landing Harber mouth in 1946, which increased tidal flux from seasonal to daily. Previous studies have dacumented rapid and accelerating rates of tidal flow, erosion and habitat loss along the main channel, and a variety of management actions are now b Estuarine Research Reserve (ESNERR) (Broenkow and Breaker 2005 and Bildstein et, al. 2001). Malzone (1999) compared bathymetric data from 1988 ta 1993, which indicated a sediment lass of Sx104 m3/yr. Two fallaw up studies, conducted by Sampey (2005) and Dean (2003] concluded that between 2001 and 2003 the Slough continued to erode at 1.5 times the annual rate cakulated by Malzone. being considered by the Elkhorn Slough National erosion accurring in the seaf these studies documented an overall deepening of the central channel with the hiest rates of Dimit d half of the slaugh west af the Parsans Slough mauth (zanes 1-4), with significant but lower rates faund in the mid slough (zanes 5-6) and low to no erosion accurring towards the head (zones 7-8). ESNERR initiated the Elkharn Slough Tidal Wetlands Project (ESTWP) to recommend management solutions to halt or reverse these processes (Caffrey et. al. 2002). The goal af the present study is to determine whether the spatial pattem and rates of tidal scour and erosion have changed since the 200a survey Zane? Cros-sectios 19-0s A time series analysis was continued along the thalweg to determine if the rate of change in Elkhom Slough is increasing decreasing, ar reaching an equilibrium state. Using bathymetric data callected in 1993, 2001, 2003, 2005, and 2009, crass-sections were compared in the eight zones of the slough to test the following hypotheses: H1: Between 1993 and 2009, the erosion rate has increased. H2: Between 1993 and 2009, the erosion rate has slowed. Methods Assessing the rate of change within Elkharn Slough required a continuation of the time series analysis. The Seafloor Mapping Laboratory at California State University Monterey Bay (CSUMB) conducted a high resolution bathymetry and topographic survey of Elkhorn Slough using a Swathplus 200khz interferometric sidescan sonar and vessel-based Riegl i420LM terrestrial LIDAR system. HYPACK hydrographic package provided survey planning and navigation. Data from an Applanix POSMV v4 was used for positioning, attitude and tidal correction after differential correction and processing in POSPAC 5 software. Sound velocity data was collected using an SV+ profiler. Sonar and LIDAR data were exported as asci files in UTM coardinates NAD83 (CORS96) HAE and converted to NAVDSS Geaid03 using Corpscon 6. Soundings files were then converted to PFM format for CUBE cleaning in IVS Fledermaus where erroneous points were removed both manually and with filters. Cleaned soundings were exported as comma separated text files from a one meter CUBE surface, and used to create a combined bathymetric/topographic 1m DEM using ArcMap 9.2 (ESRI, 2006) covering the length of the slough. Raster subtraction was used to quantify changes in bathymetry from 2005 to 2009. Spatial changes in channel depth between 1993 and 2009 were examined using longitudinal profiles of the thalweg. Multi-year cross- sectional profile comparisons were created for each of the eight erosion zanes along the length of the Slough identified in previous studies. These profiles were used to evaluate and contrast patterns of change in widths and depths of the main channel and intertidal mudflats. Annual Erosion Rates 2005-2009 bathymetric change meterslyear -1.0- 05 0.5-04 0.4.03 03-02 Results & Conclusions 42-01 4.1-05 Overal, the Ekhorn Slough is stil daminated by erosion, but at a rate that appears to be slowing (back ground image of 2005-2009 raster subtraction resuks in annualined bathymetric change, with warm colors indicating ermion and cool colors showing deponiton - see legend for scale. Values of +-0.05m/y are below the precision of the data and have been excluded from the analysis and display). Resuks from serial pair wise raster subtractions and the profile analyses shown in example cross section graphs for each erosion zone here and desrribed below indicate that while there is still a head to mouth gradient of increasing ermsion along the thalweg. particubrty west of Parsons Slough (zones 1-41, the rates are now diminishing from what they were in past years. Moreover, through the novel application of mobile marine topagraphic LIDAR there is compeling evidence of signiřicant sediment deposition on the mudlats. 0.05 -0 0.06 -0.1 0.1-0.2 ZONE 1- Dramatic deepening > 2m) and widening (20m) from 1993 to 2001, with continued down cutting from 2008 to 2005 at a slower rate, and no further down cutting occurred after 2005. There is some evidence of the main channel wldening after 2005, and the mudtlats continuing to shoal since 2001 (05m) after first eroding between 1993 and 2001 ( 0Sm) ZONE 2- Dramatic down outting ( 2m) and widening (30m) of main channel from 1993 to 2005 with change over the next four years to 2009 Continued deposition im) on mudlats of narthern share after initial erosion between 1993 and 2001 (OSm). ZONE 3- Dramatic de E4.Pacnor epening la 2m) and widening of the cross sectional area from 1993 to 2005 with Ittle change between 2005 and 2009. 02-0.3 03-0.4 04 -0.5 a5-1 Slough mouth has erpariencad the h e hiahest erosion rates recorded in the siouah, with the areatast chanze accuming from 1993 to 2001 (> 2.5m), and continued down cutting through 2003 and another increase in erosion rates from 2005 to 2009 (0.5m). ZONE S - Very ittle change along manit of the thalwng over the years, but some dawn cutting 0 75m) and widening (10m) from 1993 to 2005 in creis section fallowed by Iittle change through 2009. Possible deposition (c0.25m) within the main channel has occurred from 2003 to 2009, but this relatively small change may be below the precision of our analysis. The mudnats have shoaled between 1993 and 2000. ZONE G-St less change in this zone along the thalweg from 1993 to 2009 (< 0.Sm), Little change from 1993 to 2001, wth the only jump in down cutting in the main channel from 2001 to 2003, followed by no apparent change in the main channel cross section from 2003 to 2009. The mudfians, however, have received measurable depostion (05m) ZONE 7-No detectable change along the thalweg apart from some channel migration and minor widening at bends. Measurable depostion has occurred on the mudflats (up to 0.5m). ZONE 8 - There appears to have been some minor down cutting ( O.5m) in the main channel between 1993 and 2003, followed by deposition in both the main channel and on the mud flats through 2009 Elkhorn Slough Thalweg 1993-2009 zone 1 zone 2 zone 3 zone 5 zone 8 zone 7 Zone4 Cross section 1993-2009 Zons 1 Cross-sectian 1953-2000 Jane 2Oren seoloe Zene 4 Parnora Sleugh Thahwag1903-20m Bathymetric Time Series Analysis of Tidal Scour Rates in Elkhorn Slough 1993- 2009 MAPPING APLOOR Direen, R., Frame, J., Galvan, J., Gonzalez, G., Hall, A., Hosler, C., Jones, A., Sandersfeld, M., Stoner, K. , Wrubel, K. Undergraduate Class Project ENVS 433 Applied Coastal Remote Sensing - California State University, Monterey Bay 100 Campus Center, Seaside, CA 93955 USA Introduction Jone& Cross-section 1993-2009 Over the past 100 years S0% of California's wetlands have been destrayed (Buchsbaum 2000). Wetlands are ecologically important ecosystems that provide a wide array of services that we take advantage of on a daily basis. In California, urban spread and agriculture have caused the vast majority of aur wetlands to disappear. Elkhorn Slough, one of the last remaining coastal wetlands In California, has been experiencing rapid habitat loss since the opening af the Moss Landing Harber mouth in 1946, which increased tidal flux from seasonal to daily. Previous studies have dacumented rapid and accelerating rates of tidal flow, erosion and habitat loss along the main channel, and a variety of management actions are now b Estuarine Research Reserve (ESNERR) (Broenkow and Breaker 2005 and Bildstein et, al. 2001). Malzone (1999) compared bathymetric data from 1988 ta 1993, which indicated a sediment lass of Sx104 m3/yr. Two fallaw up studies, conducted by Sampey (2005) and Dean (2003] concluded that between 2001 and 2003 the Slough continued to erode at 1.5 times the annual rate cakulated by Malzone. being considered by the Elkhorn Slough National erosion accurring in the seaf these studies documented an overall deepening of the central channel with the hiest rates of Dimit d half of the slaugh west af the Parsans Slough mauth (zanes 1-4), with significant but lower rates faund in the mid slough (zanes 5-6) and low to no erosion accurring towards the head (zones 7-8). ESNERR initiated the Elkharn Slough Tidal Wetlands Project (ESTWP) to recommend management solutions to halt or reverse these processes (Caffrey et. al. 2002). The goal af the present study is to determine whether the spatial pattem and rates of tidal scour and erosion have changed since the 200a survey Zane? Cros-sectios 19-0s A time series analysis was continued along the thalweg to determine if the rate of change in Elkhom Slough is increasing decreasing, ar reaching an equilibrium state. Using bathymetric data callected in 1993, 2001, 2003, 2005, and 2009, crass-sections were compared in the eight zones of the slough to test the following hypotheses: H1: Between 1993 and 2009, the erosion rate has increased. H2: Between 1993 and 2009, the erosion rate has slowed. Methods Assessing the rate of change within Elkharn Slough required a continuation of the time series analysis. The Seafloor Mapping Laboratory at California State University Monterey Bay (CSUMB) conducted a high resolution bathymetry and topographic survey of Elkhorn Slough using a Swathplus 200khz interferometric sidescan sonar and vessel-based Riegl i420LM terrestrial LIDAR system. HYPACK hydrographic package provided survey planning and navigation. Data from an Applanix POSMV v4 was used for positioning, attitude and tidal correction after differential correction and processing in POSPAC 5 software. Sound velocity data was collected using an SV+ profiler. Sonar and LIDAR data were exported as asci files in UTM coardinates NAD83 (CORS96) HAE and converted to NAVDSS Geaid03 using Corpscon 6. Soundings files were then converted to PFM format for CUBE cleaning in IVS Fledermaus where erroneous points were removed both manually and with filters. Cleaned soundings were exported as comma separated text files from a one meter CUBE surface, and used to create a combined bathymetric/topographic 1m DEM using ArcMap 9.2 (ESRI, 2006) covering the length of the slough. Raster subtraction was used to quantify changes in bathymetry from 2005 to 2009. Spatial changes in channel depth between 1993 and 2009 were examined using longitudinal profiles of the thalweg. Multi-year cross- sectional profile comparisons were created for each of the eight erosion zanes along the length of the Slough identified in previous studies. These profiles were used to evaluate and contrast patterns of change in widths and depths of the main channel and intertidal mudflats. Annual Erosion Rates 2005-2009 bathymetric change meterslyear -1.0- 05 0.5-04 0.4.03 03-02 Results & Conclusions 42-01 4.1-05 Overal, the Ekhorn Slough is stil daminated by erosion, but at a rate that appears to be slowing (back ground image of 2005-2009 raster subtraction resuks in annualined bathymetric change, with warm colors indicating ermion and cool colors showing deponiton - see legend for scale. Values of +-0.05m/y are below the precision of the data and have been excluded from the analysis and display). Resuks from serial pair wise raster subtractions and the profile analyses shown in example cross section graphs for each erosion zone here and desrribed below indicate that while there is still a head to mouth gradient of increasing ermsion along the thalweg. particubrty west of Parsons Slough (zones 1-41, the rates are now diminishing from what they were in past years. Moreover, through the novel application of mobile marine topagraphic LIDAR there is compeling evidence of signiřicant sediment deposition on the mudlats. 0.05 -0 0.06 -0.1 0.1-0.2 ZONE 1- Dramatic deepening > 2m) and widening (20m) from 1993 to 2001, with continued down cutting from 2008 to 2005 at a slower rate, and no further down cutting occurred after 2005. There is some evidence of the main channel wldening after 2005, and the mudtlats continuing to shoal since 2001 (05m) after first eroding between 1993 and 2001 ( 0Sm) ZONE 2- Dramatic down outting ( 2m) and widening (30m) of main channel from 1993 to 2005 with change over the next four years to 2009 Continued deposition im) on mudlats of narthern share after initial erosion between 1993 and 2001 (OSm). ZONE 3- Dramatic de E4.Pacnor epening la 2m) and widening of the cross sectional area from 1993 to 2005 with Ittle change between 2005 and 2009. 02-0.3 03-0.4 04 -0.5 a5-1 Slough mouth has erpariencad the h e hiahest erosion rates recorded in the siouah, with the areatast chanze accuming from 1993 to 2001 (> 2.5m), and continued down cutting through 2003 and another increase in erosion rates from 2005 to 2009 (0.5m). ZONE S - Very ittle change along manit of the thalwng over the years, but some dawn cutting 0 75m) and widening (10m) from 1993 to 2005 in creis section fallowed by Iittle change through 2009. Possible deposition (c0.25m) within the main channel has occurred from 2003 to 2009, but this relatively small change may be below the precision of our analysis. The mudnats have shoaled between 1993 and 2000. ZONE G-St less change in this zone along the thalweg from 1993 to 2009 (< 0.Sm), Little change from 1993 to 2001, wth the only jump in down cutting in the main channel from 2001 to 2003, followed by no apparent change in the main channel cross section from 2003 to 2009. The mudfians, however, have received measurable depostion (05m) ZONE 7-No detectable change along the thalweg apart from some channel migration and minor widening at bends. Measurable depostion has occurred on the mudflats (up to 0.5m). ZONE 8 - There appears to have been some minor down cutting ( O.5m) in the main channel between 1993 and 2003, followed by deposition in both the main channel and on the mud flats through 2009 Elkhorn Slough Thalweg 1993-2009 zone 1 zone 2 zone 3 zone 5 zone 8 zone 7 Zone4 Cross section 1993-2009 Zons 1 Cross-sectian 1953-2000 Jane 2Oren seoloe Zene 4 Parnora Sleugh Thahwag1903-20m Bathymetric Time Series Analysis of Tidal Scour Rates in Elkhorn Slough 1993- 2009 MAPPING APLOOR Direen, R., Frame, J., Galvan, J., Gonzalez, G., Hall, A., Hosler, C., Jones, A., Sandersfeld, M., Stoner, K. , Wrubel, K. Undergraduate Class Project ENVS 433 Applied Coastal Remote Sensing - California State University, Monterey Bay 100 Campus Center, Seaside, CA 93955 USA Introduction Jone& Cross-section 1993-2009 Over the past 100 years S0% of California's wetlands have been destrayed (Buchsbaum 2000). Wetlands are ecologically important ecosystems that provide a wide array of services that we take advantage of on a daily basis. In California, urban spread and agriculture have caused the vast majority of aur wetlands to disappear. Elkhorn Slough, one of the last remaining coastal wetlands In California, has been experiencing rapid habitat loss since the opening af the Moss Landing Harber mouth in 1946, which increased tidal flux from seasonal to daily. Previous studies have dacumented rapid and accelerating rates of tidal flow, erosion and habitat loss along the main channel, and a variety of management actions are now b Estuarine Research Reserve (ESNERR) (Broenkow and Breaker 2005 and Bildstein et, al. 2001). Malzone (1999) compared bathymetric data from 1988 ta 1993, which indicated a sediment lass of Sx104 m3/yr. Two fallaw up studies, conducted by Sampey (2005) and Dean (2003] concluded that between 2001 and 2003 the Slough continued to erode at 1.5 times the annual rate cakulated by Malzone. being considered by the Elkhorn Slough National erosion accurring in the seaf these studies documented an overall deepening of the central channel with the hiest rates of Dimit d half of the slaugh west af the Parsans Slough mauth (zanes 1-4), with significant but lower rates faund in the mid slough (zanes 5-6) and low to no erosion accurring towards the head (zones 7-8). ESNERR initiated the Elkharn Slough Tidal Wetlands Project (ESTWP) to recommend management solutions to halt or reverse these processes (Caffrey et. al. 2002). The goal af the present study is to determine whether the spatial pattem and rates of tidal scour and erosion have changed since the 200a survey Zane? Cros-sectios 19-0s A time series analysis was continued along the thalweg to determine if the rate of change in Elkhom Slough is increasing decreasing, ar reaching an equilibrium state. Using bathymetric data callected in 1993, 2001, 2003, 2005, and 2009, crass-sections were compared in the eight zones of the slough to test the following hypotheses: H1: Between 1993 and 2009, the erosion rate has increased. H2: Between 1993 and 2009, the erosion rate has slowed. Methods Assessing the rate of change within Elkharn Slough required a continuation of the time series analysis. The Seafloor Mapping Laboratory at California State University Monterey Bay (CSUMB) conducted a high resolution bathymetry and topographic survey of Elkhorn Slough using a Swathplus 200khz interferometric sidescan sonar and vessel-based Riegl i420LM terrestrial LIDAR system. HYPACK hydrographic package provided survey planning and navigation. Data from an Applanix POSMV v4 was used for positioning, attitude and tidal correction after differential correction and processing in POSPAC 5 software. Sound velocity data was collected using an SV+ profiler. Sonar and LIDAR data were exported as asci files in UTM coardinates NAD83 (CORS96) HAE and converted to NAVDSS Geaid03 using Corpscon 6. Soundings files were then converted to PFM format for CUBE cleaning in IVS Fledermaus where erroneous points were removed both manually and with filters. Cleaned soundings were exported as comma separated text files from a one meter CUBE surface, and used to create a combined bathymetric/topographic 1m DEM using ArcMap 9.2 (ESRI, 2006) covering the length of the slough. Raster subtraction was used to quantify changes in bathymetry from 2005 to 2009. Spatial changes in channel depth between 1993 and 2009 were examined using longitudinal profiles of the thalweg. Multi-year cross- sectional profile comparisons were created for each of the eight erosion zanes along the length of the Slough identified in previous studies. These profiles were used to evaluate and contrast patterns of change in widths and depths of the main channel and intertidal mudflats. Annual Erosion Rates 2005-2009 bathymetric change meterslyear -1.0- 05 0.5-04 0.4.03 03-02 Results & Conclusions 42-01 4.1-05 Overal, the Ekhorn Slough is stil daminated by erosion, but at a rate that appears to be slowing (back ground image of 2005-2009 raster subtraction resuks in annualined bathymetric change, with warm colors indicating ermion and cool colors showing deponiton - see legend for scale. Values of +-0.05m/y are below the precision of the data and have been excluded from the analysis and display). Resuks from serial pair wise raster subtractions and the profile analyses shown in example cross section graphs for each erosion zone here and desrribed below indicate that while there is still a head to mouth gradient of increasing ermsion along the thalweg. particubrty west of Parsons Slough (zones 1-41, the rates are now diminishing from what they were in past years. Moreover, through the novel application of mobile marine topagraphic LIDAR there is compeling evidence of signiřicant sediment deposition on the mudlats. 0.05 -0 0.06 -0.1 0.1-0.2 ZONE 1- Dramatic deepening > 2m) and widening (20m) from 1993 to 2001, with continued down cutting from 2008 to 2005 at a slower rate, and no further down cutting occurred after 2005. There is some evidence of the main channel wldening after 2005, and the mudtlats continuing to shoal since 2001 (05m) after first eroding between 1993 and 2001 ( 0Sm) ZONE 2- Dramatic down outting ( 2m) and widening (30m) of main channel from 1993 to 2005 with change over the next four years to 2009 Continued deposition im) on mudlats of narthern share after initial erosion between 1993 and 2001 (OSm). ZONE 3- Dramatic de E4.Pacnor epening la 2m) and widening of the cross sectional area from 1993 to 2005 with Ittle change between 2005 and 2009. 02-0.3 03-0.4 04 -0.5 a5-1 Slough mouth has erpariencad the h e hiahest erosion rates recorded in the siouah, with the areatast chanze accuming from 1993 to 2001 (> 2.5m), and continued down cutting through 2003 and another increase in erosion rates from 2005 to 2009 (0.5m). ZONE S - Very ittle change along manit of the thalwng over the years, but some dawn cutting 0 75m) and widening (10m) from 1993 to 2005 in creis section fallowed by Iittle change through 2009. Possible deposition (c0.25m) within the main channel has occurred from 2003 to 2009, but this relatively small change may be below the precision of our analysis. The mudnats have shoaled between 1993 and 2000. ZONE G-St less change in this zone along the thalweg from 1993 to 2009 (< 0.Sm), Little change from 1993 to 2001, wth the only jump in down cutting in the main channel from 2001 to 2003, followed by no apparent change in the main channel cross section from 2003 to 2009. The mudfians, however, have received measurable depostion (05m) ZONE 7-No detectable change along the thalweg apart from some channel migration and minor widening at bends. Measurable depostion has occurred on the mudflats (up to 0.5m). ZONE 8 - There appears to have been some minor down cutting ( O.5m) in the main channel between 1993 and 2003, followed by deposition in both the main channel and on the mud flats through 2009 Elkhorn Slough Thalweg 1993-2009 zone 1 zone 2 zone 3 zone 5 zone 8 zone 7 Zone4 Cross section 1993-2009 Zons 1 Cross-sectian 1953-2000 Jane 2Oren seoloe Zene 4 Parnora Sleugh Thahwag1903-20m