Puerto Rico Landslide Monitoring Network Active

Hurricane Maria made landfall on the main island of Puerto Rico on 20 September 2017 and triggered more than 70,000 landslides in at least three-fourths of Puerto Rico’s 78 municipalities (Hughes et al., 2019). The number of landslides that occurred during this event was two orders of magnitude greater than those reported from previous hurricanes. Most Maria-triggered landslides were shallow (less than 1 m deep; Baxstrom et al., 2021a, 2021b; Bessette-Kirton et al., 2019; Einbund et al., 2021a, 2021b) and occurred during and soon after intense rainfall. Many of the landslides transitioned into debris flows that presented hazards far from where the slides initiated. Steep slopes in hilly and mountainous regions were particularly impacted by landslides, and especially where estimated soil moisture was greatest (Hughes and Schulz, 2020). Soil moisture, pore-water pressures, and soil properties strongly determine the propensity for landsliding, so knowledge of these conditions is critical to reducing risk and loss from landslide hazards. The following displays the data obtained from twelve hydrological monitoring sites distributed across the island. 

Sources/Usage: Public Domain.

Designed and installed in collaboration with the University of Puerto Rico-Mayagüez, the monitoring network was developed to reveal conditions representative of many landslide-prone regions of Puerto Rico. The stations generally measure rainfall using either a TB4 tipping bucket with 0.1 mm resolution and at 0-250 mm/hr or 250-50 mm/hr, with accuracy of +2% and +3%, respectively, or a TE525-L rain gauge with 1 tip resolution and accuracy +1% up to 1 in/hr (gauges from Texas Electronics). Air pressure is measured using either Geokon vibrating wire piezometers (4500AL-70kPa type with 0.025% F.S. resolution and +0.1% F.S. accuracy) or a Campbell Scientific CS106 barometer with accuracy of +0.3 hPa, +0.6 hPa, +1.0 hPa, and +1.5 hPa at +20^oC, 0-40^oC, -20^o - +45^oC and -40^o - +60^oC, respectively. Air temperature is measured using Geokon vibrating wire piezometers (4500AL-70kPa type) with temperature accuracy from –20^oC to 80^oC, and resolution of 0.025% F.S. minimum.

Subsurface sensors were installed into the uphill wall of hand-excavated pits generally ~1 m deep, which were subsequently backfilled following sensor installation. Stations generally measure soil moisture at four depths using Meter Teros 10 soil water content sensors with an accuracy of +0.03 m³/m³ and a resolution of 0.0010 m³/m³, suction stress at three depths using Meter Teros 21 soil water potential sensors with an accuracy of  +(10% of reading + 2 kPa) from –100 to –5 kPa and a resolution of 0 kPa, and total fluid pressure at the maximum excavation depth using Geokon model 4500AL-70kPa standard piezometers with 0.025% F.S. resolution and +0.1% F.S. accuracy (pressure was offset to zero during sensor installation).

The stations are solar- and battery-powered and equipped with cellular telemetry. Geologists with the University of Puerto Rico-Mayagüez maintain these sensors and stations to help ensure they remain operational in the challenging jungle environment, where complications such as harsh weather, rapidly growing vegetation, and animals can alter data collection and/or damage monitoring equipment. The data from these monitoring stations is currently being used to develop a landslide forecasting and alerting system, and to aid landslide research in Puerto Rico. 

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