The West Hills of Portland, in the southern Tualatin Mountains, trend northwest along the west side of Portland, Oregon. These silt-mantled mountains receive significant wet-season precipitation and are prone to sliding during wet conditions, occasionally resulting in significant property damage or casualties. In an effort to develop a baseline for interpretive analysis of the groundwater response to rainfall, an automated monitoring system was installed in 2006 to measure rainfall, pore-water pressure, soil suction, soil-water potential, and volumetric water content at 15-minute intervals. The data show a cyclical pattern of groundwater and moisture content levels—wet from October to May and dry between June and September. Saturated soil conditions tend to last throughout the wet season. This release presents data collected from January 10, 2006, through January 23,2017.

We performed hourly monitoring of conditions at the Two Towers landslide located in northern California near the town of Zenia. Monitored conditions included rainfall, groundwater head, horizontal total stress, horizontal effective stress, vertical soil deformation, and subsurface displacement. Data were acquired November 11, 2014–July 22, 2017, except for times during which power failure occurred; data for these times are given as “NAN” (not a number). Rainfall data are provided in millimeters during the past hour (mm/hr). Groundwater heads are provided in meters (m) above the landslide base. Horizontal stresses are provided in kilopascals (kPa). Vertical soil deformation data are provided in terms of length (centimeters, cm) of the sensor. Cumulative landslide displacement is provided in millimeters (mm). Rainfall was measured at the landslide middle monitoring location using a tipping-bucket rain gauge with resolution of 0.254 mm and accuracy of ±2% to 250 mm/hr (resolutions and accuracies stated herein are as specified by sensor manufacturers and accounting for datalogger resolution). A vibrating-wire total-stress plate sensor was installed with near-vertical orientation in the floor of an excavated pit at the middle monitoring location. This sensor measured total horizontal stress applied to its 230-mm-diameter surface with resolution of 0.014 kPa and accuracy of ±0.069 kPa. The sensor was installed within a slot slightly wider than the plate itself with its center at a depth of 1.83 m, and a vibrating-wire fluid pressure transducer with the same resolution and accuracy as the total stress sensor was installed adjacent to the cell to measure fluid pressure and therefore provide a means of calculating horizontal effective stress. The pit was backfilled after sensor installation with material removed during its excavation. The remaining sensors were installed within 6.35-cm-diameter holes bored using hand equipment. These included electronic, vibrating-wire fluid pressure transducers (piezometers) with resolutions of 0.014 kPa and 0.086 kPa, and respective accuracies of ±0.069 kPa and ±0.344 kPa. Boreholes were backfilled above transducers first with ~0.3 m of material obtained during boring followed by bentonite granules to the ground surface. Piezometers were installed at depths of 3.66 m and 6.07 m at the upper monitoring location, 3.95 m and 5.69 m at the middle monitoring location, and 2.62 and 3.66 m at the lower monitoring location. Landslide basal depths were identified at approximately 6.3 m, 7.9 m, and 3.6 m at the upper, middle, and lower monitoring locations, respectively. A 30.48-cm-long biaxial tilt sensor installed within PVC casing (slope inclinometer) was used to monitor landslide displacement at the lower monitoring location. The slope inclinometer has 0.003 mm displacement resolution and long-term displacement accuracy of ±0.23 mm. A vibrating-wire length sensor was installed in a borehole to measure near-surface vertical deformation at the middle monitoring location. This sensor measured length with 0.0375 mm resolution and ±0.15 mm accuracy. The sensor’s upper and lower ends were anchored within cement grout such that its length was measured over a depth range (at installation) of 0.20-1.72 m. All sensors contain thermistors and readings are temperature compensated, with the exception of the rain gauge. These data support a study described in Schulz, W.H., Smith, J.B., Wang, G., Jiang, Y., and Roering, J.J., 2018, Clayey landslide initiation and acceleration strongly modulated by soil swelling: Geophysical Research Letters, DOI:10.1002/2017GL076807.

We performed hourly monitoring of conditions at the Two Towers landslide located in northern California near the town of Zenia. Monitored conditions included rainfall, groundwater head, horizontal total stress, horizontal effective stress, vertical soil deformation, and subsurface displacement. Data were acquired November 11, 2014–July 22, 2017, except for times during which power failure occurred; data for these times are given as “NAN” (not a number). Rainfall data are provided in millimeters during the past hour (mm/hr). Groundwater heads are provided in meters (m) above the landslide base. Horizontal stresses are provided in kilopascals (kPa). Vertical soil deformation data are provided in terms of length (centimeters, cm) of the sensor. Cumulative landslide displacement is provided in millimeters (mm). Rainfall was measured at the landslide middle monitoring location using a tipping-bucket rain gauge with resolution of 0.254 mm and accuracy of ±2% to 250 mm/hr (resolutions and accuracies stated herein are as specified by sensor manufacturers and accounting for datalogger resolution). A vibrating-wire total-stress plate sensor was installed with near-vertical orientation in the floor of an excavated pit at the middle monitoring location. This sensor measured total horizontal stress applied to its 230-mm-diameter surface with resolution of 0.014 kPa and accuracy of ±0.069 kPa. The sensor was installed within a slot slightly wider than the plate itself with its center at a depth of 1.83 m, and a vibrating-wire fluid pressure transducer with the same resolution and accuracy as the total stress sensor was installed adjacent to the cell to measure fluid pressure and therefore provide a means of calculating horizontal effective stress. The pit was backfilled after sensor installation with material removed during its excavation. The remaining sensors were installed within 6.35-cm-diameter holes bored using hand equipment. These included electronic, vibrating-wire fluid pressure transducers (piezometers) with resolutions of 0.014 kPa and 0.086 kPa, and respective accuracies of ±0.069 kPa and ±0.344 kPa. Boreholes were backfilled above transducers first with ~0.3 m of material obtained during boring followed by bentonite granules to the ground surface. Piezometers were installed at depths of 3.66 m and 6.07 m at the upper monitoring location, 3.95 m and 5.69 m at the middle monitoring location, and 2.62 and 3.66 m at the lower monitoring location. Landslide basal depths were identified at approximately 6.3 m, 7.9 m, and 3.6 m at the upper, middle, and lower monitoring locations, respectively. A 30.48-cm-long biaxial tilt sensor installed within PVC casing (slope inclinometer) was used to monitor landslide displacement at the lower monitoring location. The slope inclinometer has 0.003 mm displacement resolution and long-term displacement accuracy of ±0.23 mm. A vibrating-wire length sensor was installed in a borehole to measure near-surface vertical deformation at the middle monitoring location. This sensor measured length with 0.0375 mm resolution and ±0.15 mm accuracy. The sensor’s upper and lower ends were anchored within cement grout such that its length was measured over a depth range (at installation) of 0.20-1.72 m. All sensors contain thermistors and readings are temperature compensated, with the exception of the rain gauge. These data support a study described in Schulz, W.H., Smith, J.B., Wang, G., Jiang, Y., and Roering, J.J., 2018, Clayey landslide initiation and acceleration strongly modulated by soil swelling: Geophysical Research Letters, DOI:10.1002/2017GL076807.

This data release includes time-series data and qualitative descriptions from a monitoring station on a steep, landslide-prone slope above the City of Sitka, Alaska. On August 18, 2015, heavy rainfall triggered around 60 landslides in and around Sitka. These landslides moved downslope rapidly; several were damaging, and one demolished a home on South Kramer Avenue and killed three people. On September 16-18, 2019, the U.S. Geological Survey installed instrumentation at a site near the initiation zones of these landslides and other previous landslides on the west face of Harbor Mountain. The station consists of an electronics enclosure, a mounted rain gage, and two instrumented soil pits. Instruments record continuous measurements of precipitation, air temperature, volumetric water content, pore-water pressure, soil temperature, and soil matric potential at five-minute intervals. Soil pits were dug as deep as possible into the soil mantle for installation of the hydrologic monitoring instruments. Extensive probing with a 1.2-m-long piece of rebar to the point of refusal confirmed that the bottom of each hole was near the top of bedrock or compact till. The first soil pit (SP1), located at N 57.08551, W 135.35936, is about 1 m downslope from the north rim of the drainage hollow. SP1 is about 60 cm deep with the upper 12-15 cm in dark brown, moist, silty sand with large concentration of plant roots. Below 15 cm, to bottom of hole, consists of abundant gray sandstone clasts in silty sand matrix, which ranges in color from orange-brown, brown, to gray. The SP1 sensor array consists of a water potential sensor and soil moisture sensor at 25 cm depth, a second soil moisture sensor at 50 cm depth, and a pressure transducer near bottom of hole with a port at ~55 cm depth. The second soil pit (SP2), located at N 57.08548, W 135.35933, is about 5 m downslope from the north rim of the drainage hollow and is 65 cm deep. The top of hard material (bedrock or till) was about 70 cm deep, but there was free water at a depth of about 50-55 cm. Material throughout the depth of the hole was moist sandy silty clay of a gelatinous consistency. Color ranged from orange-brown to dark brown. Very few stones were present. These soils were interpreted as transported/mixed, weathered volcanic ash (Jacqueline Foss, USDA Forest Service, personal communication, 2019). The SP2 sensor array consists of soil moisture sensors at 25 and 40 cm depth, and a pressure transducer lying on the bottom of the hole, with a port at about 60 cm depth. A Campbell Scientific CR1000 datalogger is used to collect continuous data from these sensors. The datalogger and modem are contained in a sealed, weather-resistant fiberglass enclosure. The CR1000 datalogger contains an internal thermistor that continuously measures temperature. Additionally, an air temperature sensor was installed to collect continuous air temperature data. A tipping bucket rain gage installed in a clearing about 10 m northwest of the logger enclosure collects precipitation data. The maximum resolution of the rain gauge is 0.2 mm; that is, one tip of the bucket represents 0.2 mm. Four METER ECH20 EC-5 sensors are used to collect soil moisture data. Pore-water pressures are measured using two Campbell Scientific CS-451 pressure transducers. A METER MPS-6 water potential sensor in SP1 is used to collect soil matric potential. This sensor’s measurements range from -100,000 to -9 kPa was exceeded for the duration of the monitoring period. Recorded values appear to hover around the sensor’s upper limit (-9 kPa), with the exception of September 2019 when the station was first installed and a few brief periods in July 2022 when conditions were sufficiently dry for matric potentials to drop below -9 kPa. The water potential sensor and pressure sensors have integrated thermistors and the associated temperature readings are included. Several factors that may influence data consistency and/or quality should be

This data release includes time-series data and qualitative descriptions from a monitoring station on a steep, landslide-prone slope above the City of Sitka, Alaska. On August 18, 2015, heavy rainfall triggered around 60 landslides in and around Sitka. These landslides moved downslope rapidly; several were damaging, and one demolished a home on South Kramer Avenue and killed three people. On September 16-18, 2019, the U.S. Geological Survey installed instrumentation at a site near the initiation zones of these landslides and other previous landslides on the west face of Harbor Mountain. The station consists of an electronics enclosure, a mounted rain gage, and two instrumented soil pits. Instruments record continuous measurements of precipitation, air temperature, volumetric water content, pore-water pressure, soil temperature, and soil matric potential at five-minute intervals. Soil pits were dug as deep as possible into the soil mantle for installation of the hydrologic monitoring instruments. Extensive probing with a 1.2-m-long piece of rebar to the point of refusal confirmed that the bottom of each hole was near the top of bedrock or compact till. The first soil pit (SP1), located at N 57.08551, W 135.35936, is about 1 m downslope from the north rim of the drainage hollow. SP1 is about 60 cm deep with the upper 12-15 cm in dark brown, moist, silty sand with large concentration of plant roots. Below 15 cm, to bottom of hole, consists of abundant gray sandstone clasts in silty sand matrix, which ranges in color from orange-brown, brown, to gray. The SP1 sensor array consists of a water potential sensor and soil moisture sensor at 25 cm depth, a second soil moisture sensor at 50 cm depth, and a pressure transducer near bottom of hole with a port at ~55 cm depth. The second soil pit (SP2), located at N 57.08548, W 135.35933, is about 5 m downslope from the north rim of the drainage hollow and is 65 cm deep. The top of hard material (bedrock or till) was about 70 cm deep, but there was free water at a depth of about 50-55 cm. Material throughout the depth of the hole was moist sandy silty clay of a gelatinous consistency. Color ranged from orange-brown to dark brown. Very few stones were present. These soils were interpreted as transported/mixed, weathered volcanic ash (Jacqueline Foss, USDA Forest Service, personal communication, 2019). The SP2 sensor array consists of soil moisture sensors at 25 and 40 cm depth, and a pressure transducer lying on the bottom of the hole, with a port at about 60 cm depth. A Campbell Scientific CR1000 datalogger is used to collect continuous data from these sensors. The datalogger and modem are contained in a sealed, weather-resistant fiberglass enclosure. The CR1000 datalogger contains an internal thermistor that continuously measures temperature. Additionally, an air temperature sensor was installed to collect continuous air temperature data. A tipping bucket rain gage installed in a clearing about 10 m northwest of the logger enclosure collects precipitation data. The maximum resolution of the rain gauge is 0.2 mm; that is, one tip of the bucket represents 0.2 mm. Four METER ECH20 EC-5 sensors are used to collect soil moisture data. Pore-water pressures are measured using two Campbell Scientific CS-451 pressure transducers. A METER MPS-6 water potential sensor in SP1 is used to collect soil matric potential. This sensor’s measurements range from -100,000 to -9 kPa was exceeded for the duration of the monitoring period. Recorded values appear to hover around the sensor’s upper limit (-9 kPa), with the exception of September 2019 when the station was first installed and a few brief periods in July 2022 when conditions were sufficiently dry for matric potentials to drop below -9 kPa. The water potential sensor and pressure sensors have integrated thermistors and the associated temperature readings are included. Several factors that may influence data consistency and/or quality should be

A hydrologic monitoring network was installed to investigate landslide hazards affecting the railway corridor along the eastern shore of Puget Sound between Seattle and Everett, near Mukilteo, Washington. During the summer of 2015, the U.S. Geological Survey installed instrumentation at four sites to measure rainfall and air temperature every 15 minutes. Two of the four sites are installed on contrasting coastal bluffs, one landslide scarred and one vegetated. At these two sites, in addition to rainfall and air temperature, volumetric water content, pore pressure, soil suction, soil temperature (via hydrologic instrumentation), and barometric pressure were measured every 15 minutes. The instrumentation was designed to supplement landslide-rainfall thresholds developed by the U.S. Geological Survey with a long-term goal of advancing the understanding of the relationship between landslide potential and hydrologic forcing along the coastal bluffs. Additionally, the system was designed to function as a prototype monitoring system to evaluate criteria for site selection, instrument selection, and placement of instruments. Two files are included with this release. A comma separated value (csv) file contains monitoring data for the time-periods described by its name, for example 20150711_20160809.csv contains data for the period between July 11, 2015 and August 9, 2016. A read-me file (readme.doc) describes the sensor naming convention used for column names in the data files. The following citation relates to a report that provides background information and is intended to accompany this data release. Smith, J.B.; Baum, R.L.; Mirus, Benjamin B.; Michel, Abigail R.; Stark, Ben, 2017, Results of Hydrologic Monitoring on Landslide-Prone Coastal Bluffs Near Mukilteo Washington: U.S. Geological Survey Open-File Report 2017-1095, 50 p., http://dx.doi.org/10.3133/ofr20171095

A hydrologic monitoring network was installed to investigate landslide hazards affecting the railway corridor along the eastern shore of Puget Sound between Seattle and Everett, near Mukilteo, Washington. During the summer of 2015, the U.S. Geological Survey installed instrumentation at four sites to measure rainfall and air temperature every 15 minutes. Two of the four sites are installed on contrasting coastal bluffs, one landslide scarred and one vegetated. At these two sites, in addition to rainfall and air temperature, volumetric water content, pore pressure, soil suction, soil temperature (via hydrologic instrumentation), and barometric pressure were measured every 15 minutes. The instrumentation was designed to supplement landslide-rainfall thresholds developed by the U.S. Geological Survey with a long-term goal of advancing the understanding of the relationship between landslide potential and hydrologic forcing along the coastal bluffs. Additionally, the system was designed to function as a prototype monitoring system to evaluate criteria for site selection, instrument selection, and placement of instruments. Two files are included with this release. A comma separated value (csv) file contains monitoring data for the time-periods described by its name, for example 20150711_20160809.csv contains data for the period between July 11, 2015 and August 9, 2016. A read-me file (readme.doc) describes the sensor naming convention used for column names in the data files. The following citation relates to a report that provides background information and is intended to accompany this data release. Smith, J.B.; Baum, R.L.; Mirus, Benjamin B.; Michel, Abigail R.; Stark, Ben, 2017, Results of Hydrologic Monitoring on Landslide-Prone Coastal Bluffs Near Mukilteo Washington: U.S. Geological Survey Open-File Report 2017-1095, 50 p., http://dx.doi.org/10.3133/ofr20171095

We performed hourly monitoring of precipitation and soil moisture at the Two Towers landslide located in northern California near the town of Zenia. Data were acquired January 19, 2017 to April 29, 2020. Rainfall was measured near the center of the landslide using a tipping-bucket rain gauge with resolution of 0.254 mm and accuracy of ±2% to 250 mm/h (resolutions and accuracies stated herein are as specified by sensor manufacturers and accounting for datalogger resolution). Soil moisture (volumetric ratio of water volume to total volume; unitless) was measured near the center of the landslide using a dielectric sensor installed at 19-cm depth into the wall of a hand-excavated pit that was subsequently backfilled using material obtained during excavation. The soil-moisture sensor utilized factory calibration and has resolution of 0.001 and accuracy of +/- 0.03. These data support a study described in Liao, T.-H., Kim, S.-B., Handwerger, A.L., Fielding, E.J., Cosh, M., and Schulz, W.H., 2021, High-resolution soil moisture maps over landslide regions in northern California grassland derived from SAR backscattering coefficients: IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 10.1109/JSTARS.2021.3069010.

We performed hourly monitoring of precipitation and soil moisture at the Two Towers landslide located in northern California near the town of Zenia. Data were acquired January 19, 2017 to April 29, 2020. Rainfall was measured near the center of the landslide using a tipping-bucket rain gauge with resolution of 0.254 mm and accuracy of ±2% to 250 mm/h (resolutions and accuracies stated herein are as specified by sensor manufacturers and accounting for datalogger resolution). Soil moisture (volumetric ratio of water volume to total volume; unitless) was measured near the center of the landslide using a dielectric sensor installed at 19-cm depth into the wall of a hand-excavated pit that was subsequently backfilled using material obtained during excavation. The soil-moisture sensor utilized factory calibration and has resolution of 0.001 and accuracy of +/- 0.03. These data support a study described in Liao, T.-H., Kim, S.-B., Handwerger, A.L., Fielding, E.J., Cosh, M., and Schulz, W.H., 2021, High-resolution soil moisture maps over landslide regions in northern California grassland derived from SAR backscattering coefficients: IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 10.1109/JSTARS.2021.3069010.

This data release contains (1) geotechnical reports describing colluvium strength and grain size distribution, (2) hydrological monitoring data (rainfall and soil volumetric water content), and (3) shapefiles of mapped landslides from 1996 and 2021 that occurred in the Columbia River Gorge, Oregon. The geotechnical reports describe test results from a sieve and hydrometer analysis (ASTM D422) to characterize the grain size distribution and from consolidated drained direct shear tests (ASTM D3080) to characterize soil shear strength. Hydrological data includes a time history of rainfall and volumetric water content from a monitoring station in the Columbia River Gorge, spanning 10/28/2022 to 2/13/2023. The mapped landslide shapefiles represent shallow landslide source areas, assumed to have failed during storms in 1996 and 2021.