Glissements de terrain déclenchés par le tremblement de terre du 14 août 2021, de magnitude 7,2 à Nippes, Haïti

U.S. Department of the Interior U.S. Geological Survey Open-File Report 2021–1112 Earthquake Hazards Program and Landslide Hazards Program Landslides Triggered by the August 14, 2021, Magnitude 7.2 Nippes, Haiti, Earthquake Landslides Triggered by the August 14, 2021, Magnitude 7.2 Nippes, Haiti, Earthquake By Sabrina N. Martinez, Kate E. Allstadt, Stephen L. Slaughter, Robert Schmitt, Elaine Collins, Lauren N. Schaefer, and Sonia Ellison Earthquake Hazards Program and Landslide Hazards Program Open-File Report 2021–1112 U.S. Department of the Interior U.S. Geological Survey U.S. Geological Survey, Reston, Virginia: 2021 For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment—visit https://www.usgs.gov or call 1–888–ASK–USGS. For an overview of USGS information products, including maps, imagery, and publications, visit https://store.usgs.gov/ . Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner. Suggested citation: Martinez, S.N., Allstadt, K.E., Slaughter, S.L., Schmitt, R., Collins, E., Schaefer, L.N., and Ellison, S., 2021, Landslides triggered by the August 14, 2021, magnitude 7.2 Nippes, Haiti, earthquake: U.S. Geological Survey Open-File Report 2021–1112, 17 p., https://doi.org/ 10.3133/ ofr20211112 . Associated data for this publication: Martinez, S.N., Allstadt, K.E., Slaughter, S.L., Schmitt, R.G., Collins, E., Schaefer, L.N., and Ellison, S., 2021, Rapid response landslide inventory for the 14 August 2021 M7.2 Nippes, Haiti, earthquake: U.S. Geological Survey data release, https://doi.org/ 10.5066 /P99MYPXK . ISSN 2331-1258 (online) iii Acknowledgments Funding for the preparation of this report was provided by the U.S. Agency for International Development’s Bureau for Humanitarian Assistance and the U.S. Geological Survey. We thank Robert Mason, Karl Winters, and Allen Gellis for their insights on channel sedimentation and flooding and Jeff Coe, Randall Jibson, David Wald, and Ryan Gold for reviewing the report (U.S. Geological Survey). v Contents Acknowledgments ........................................................................................................................................ iii Abstract ........................................................................................................................................................... 1 Introduction ..................................................................................................................................................... 1 Data and Analysis .......................................................................................................................................... 3 Coseismic Landslides .................................................................................................................................... 4 Ongoing Hazards .......................................................................................................................................... 13 Landslide Dams ................................................................................................................................... 13 Landslide Hazards to Roads .............................................................................................................. 13 Increased Landslide Activity ............................................................................................................ 13 Channel Sedimentation and Flooding .............................................................................................. 14 Summary ........................................................................................................................................................ 15 References Cited .......................................................................................................................................... 16 Figures 1. Overview of the Tiburon Peninsula showing contours of estimated peak ground acceleration for the 2021 Nippes, Haiti, earthquake .............................................................. 2 2. Overview map of the Haiti 2021 earthquake landslide inventory showing landslide dams, road hazards, and flagged landslides .......................................................... 3 3. Flagged landslide features in Camp-Perrin commune, identified from satellite imagery after the 2021 Haiti earthquake ................................................................................... 8 4. Flagged landslide features in Pestel, Beaumont, Chantal, and Roseaux communes, identified from satellite imagery after the 2021 Haiti earthquake ................... 9 5. Flagged landslide features in Maniche commune, identified from satellite imagery after the 2021 Haiti earthquake ................................................................................. 10 6. Flagged landslide features in L’Asile commune, identified from satellite imagery after the 2021 Haiti earthquake ................................................................................................ 11 7. Flagged landslides in Cavaillon, Saint Louis du Sud, and Baradères communes, identified from satellite imagery after the 2021 Haiti earthquake ....................................... 12 8. Satellite imagery from Haiti after the 2021 earthquake and examples of two landslide dams that were flagged as warranting continued monitoring .......................... 14 9. Map showing the relative density of landslides along 1,000-meter river segments on the Tiburon Peninsula, Haiti, after the 2021 earthquake .............................. 15 Table 1. Notable landslide dams and road obstructions after the 2021 Nippes, Haiti, earthquake ..................................................................................................................................... 5 vi Conversion Factors International System of Units to U.S. customary units Multiply By To obtain Length meter (m) 3.281 foot (ft) kilometer (km) 0.6214 mile (mi) kilometer (km) 0.5400 mile, nautical (nmi) meter (m) 1.094 yard (yd) Area square kilometer (km 2 ) 247.1 acre square kilometer (km 2 ) 0.3861 square mile (mi 2 ) Datum Coordinate information is referenced to the World Geodetic System 1984 (WGS 84) Universal Transverse Mercator (UTM) Zone 18N projection. Abbreviations DART disaster assistance response team DEM digital elevation model g acceleration of gravity M magnitude RMT response management team UNICEF United Nations Children's Fund USAID U.S. Agency for International Development USGS U.S. Geological Survey UTC coordinated universal time UTM Universal Transverse Mercator WGS World Geodetic System Landslides Triggered by the August 14, 2021, Magnitude 7.2 Nippes, Haiti, Earthquake By Sabrina N. Martinez, 1 Kate E. Allstadt, 1 Stephen L. Slaughter, 1 , 2 Robert Schmitt, 1 Elaine Collins, 1 Lauren N. Schaefer, 1 and Sonia Ellison 1 1 U.S. Geological Survey 2 U.S. Agency for International Development, Bureau for Humanitarian Assistance Abstract The August 14, 2021, magnitude 7.2 Nippes, Haiti, earthquake triggered thousands of landslides on the Tiburon Peninsula. The landslides directly caused fatalities and damage and impeded response efforts by blocking roads and causing other infrastructure damage. Adverse effects of the landslides likely will continue for months to years. This report presents an assessment of potential postearthquake landslide-related geologic hazards for the Tiburon Peninsula and a preliminary map of the landslides triggered by the earthquake. This hazard assessment is based on an emergency analysis of the currently available, postearthquake satellite imagery. In this report, we highlight specific areas of concern that may benefit from more detailed assessment and longer-term monitoring. Our mapping efforts revealed that at least 4,893 landslides were triggered across the Tiburon Peninsula by the earthquake and subse - quent rainfall from Tropical Cyclone Grace. We also observed hundreds of landslide deposits potentially restricting flow in rivers and streams. In addition, we observed landslides that likely affected roads by rendering them impassable or suscep - tible to subsequent damage from existing landslides. Because of the preliminary nature of this report and the limits of remote analyses, additional investigation and monitoring would be beneficial to accurately determine the threat posed by these hazards to people and infrastructure. Introduction The magnitude ( M ) 7.2 Nippes, Haiti, earthquake occurred at 12:29:08 coordinated universal time (08:29:08 local time) on August 14, 2021. The rupture started in the center of the Tiburon Peninsula, about 125 kilometers (km) west of the capital, Port-au-Prince, and ruptured primarily westward with reverse and left-lateral strike-slip motion along the Enriquillo-Plantain Garden fault zone. The fault rup - ture terminated in the vicinity of Pic Macaya National Park. Shaking was estimated by the U.S. Geologial Survey (USGS) ShakeMap (ver. 14) to have exceeded 0.5 g (acceleration of gravity) along an 80-km band of steep and rugged, and there - fore landslide-susceptible, terrain in the center of the Tiburon Peninsula ( fig. 1 ). The USGS near-real-time ground failure product ( Allstadt and others, 2021 ) estimated that the land - slides triggered by the Nippes earthquake would be significant in number and (or) spatial extent (estimated at about 70 square kilometers) and that the number of people living near landslide hazards was significant (estimated at about 9,000 people). The landslide probability map produced by the ground failure product is shown in figure 1 . The earthquake was followed by Tropical Cyclone Grace, which was estimated to have dropped 5–10 inches of rain in Haiti on August 16, 2021 ( National Oceanic and Atmospheric Administration, 2021 ), and likely triggered additional landslides. More information about the earthquake, including the near-real-time products, is available from the USGS earthquake event page at https:// earthquake .usgs.gov/ earthquakes/ eventpage/ us6000f65h/ executive . During the week following the earthquake, a team of USGS scientists rapidly mapped landslides using remote methods and created a landslide inventory. By the end of this effort, 3,625 landslides had been mapped. This inven - tory, with critical daily observations, was shared with the U.S. Agency for International Development’s (USAID’s) Disaster Assistance Response Team (DART) and Response Management Team (RMT) for situational awareness and emergency response. The inventory also was made publicly available as an ArcGIS online web map for use by humanitar - ian aid organizations for situational awareness and emergency response. The original rapid inventory that was available immediately after the earthquake for situational awareness only is now superseded by the inventory associated with this report ( Martinez and others, 2021 ). For this report, we mapped additional landslides that were missed in the initial inventory. We carefully reviewed the inventory in its entirety to identify landslides that may pose ongoing threats to people and property ( fig. 2 ). We mapped, as best as possible, the location of each landslide’s heads - carp area as a point feature. Some mapped locations may be 2 Landslides Triggered by the August 14, 2021, Magnitude 7.2 Nippes, Haiti, Earthquake imprecise because of the poor orthorectification of some of the satellite imagery used. Landslide polygons were not mapped for this preliminary version of the inventory. Most imagery available for the affected area was obtained after the passage of Tropical Cyclone Grace; thus, the landslide inventory pre - sented could contain both earthquake- and rainfall-triggered landslides. However, we did not see many landslides with characteristics common to rainfall-triggered landslides, such as channelized flows, so we think that most of the landslides were triggered by the earthquake. In addition to landslide headscarp locations, we present an assessment of potential postearthquake landslide-related geologic hazards for the Tiburon Peninsula. We highlight specific areas of concern that may benefit from more detailed assessment and longer-term monitoring because of the poten - tial effects on people and infrastructure. Potential postearth - quake landslide hazards include (1) sudden flooding from the failure of landslide dams; (2) continued landsliding of dam - aged slopes, especially along roads and river channels; (3) an overall increase in landslide activity for multiple years; and (4) changes in river behavior from an influx of landslide sedi - ment that can lead to long-term changes in flooding risks. USGS GF model landslide probability EXPLANATION ” 0.2% 0.2–1% 1–2% 2–5% 5–10% 10–20% >20% Epicenter PGA contours Surface faults Landslide (headscarp) Landslide with >50 people within 200 m 74°24' W 18°30' N 18°06' N 74°00' W 73°36' W 73°12' W Jérémie Les Cayes Cavaillon 0.2 g 0.3 g 0.4 g 0.5 g 0.6 g 0.7 g 0.5 g 0.4 g 0.3 g 0.2 g 0.2 g 0.1 g 0.1 g Pic Macaya National Park N 0 20 KILOMETERS 5 10 15 0 5 10 MILES CARIBBEAN SEA HAITI CUBA DOMINICAN REPUBLIC PORT-AU PRINCE Tiburon Peninsula Map area Figure 1. Overview of the Tiburon Peninsula showing contours of estimated peak ground acceleration (PGA) for the 2021 Nippes, Haiti, earthquake from the U.S. Geological Survey (USGS) ShakeMap (ver. 14) overlain on the USGS Ground Failure (GF) product landslide probability model (ver. 13). The landslide probability model provides an estimate of areas where earthquake-triggered landslides were most likely to have occurred, based on the ShakeMap shaking estimates. The model is intended primarily for near-real-time use and is available at https:// earthquake .usgs.gov/ earthquakes/ eventpage/ us6000f65h/ ground- failure/ summary . Black dots show headscarp locations of mapped landslides. Green dots show where human effects may have occurred because population estimates within a 200-meter radius of a given landslide exceeded 50 people. The earthquake ruptured primarily from east to west, starting at the epicenter (yellow star). Red lines indicate location of known faults in the region from Saint Fleur and others, 2020 . N, north; W, west; g, acceleration of gravity; >, greater than; m, meter; ≤ , less than or equal to; %, percent. Data and Analysis 3 As this event shows, earthquakes can set in motion a cascade of geologic events that can affect the landscape for months (or years) following an event ( Fan and others, 2019 ). For example, in March of 2010, months after an M 7.0 earth - quake in Haiti, heavy rainfall led to flooding in Les Cayes and Cavaillon (United Nation’s Children's Fund, 2010), which resulted in mass evacuations and the deaths of eight people. The flooding was attributed to the lack of drainage from canals blocked by earthquake debris. The March 2010 event illustrates the continued effect that an earthquake can have on a landscape. It also highlights the importance of continued monitoring and additional field investigations because heavy rainfall may, in the coming months, lead to increased hazards in Haiti following the 2021 earthquake. Data and Analysis To map the landslides, we used mid- to high-resolution satellite imagery including Sentinel-2 (10-meter [m] resolu - tion), WorldView (0.3–0.5-m resolution), Planet (2.7–4.0-m resolution), and a high-resolution (1.5-m) digital elevation model (DEM) that was derived from light detection and rang - ing (lidar) collected from 2014 to 2016 (HaitiData and The World Bank, 2021). Postearthquake images were compared with pre-earthquake images to ensure the landslide feature was caused by the earthquake or the cyclone. The positional accuracy of satellite imagery can vary, especially in hilly areas or when using low-resolution imagery. Because of the vary - ing quality of imagery used and our rapid mapping for the response, we estimate our accuracy of landslide headscarp points to be within tens of meters of each landslide. In many Other landslides Haiti earthquake landslide inventory 2021 Flagged landslides Landslide dams Road hazards EXPLANATION Epicenter 18°30' N 18°15' N 74°00' W 73°45' W 73°30' W Les Cayes R1 Jérémie Esri, HERE Technologies, Garmin, U.S. Geological Survey, National Geospatial-Intelligence Agency N 0 20 KILOMETERS 5 10 15 0 5 10 MILES Figure 2. Overview map of the 2021 Nippes, Haiti, earthquake landslide inventory showing landslide dams, road hazards, and flagged landslides detailed in table 1 . The location of a series of landslides along Route Nationale 7 is labeled as R1 in the figure (R1 in table 1 ) as they occurred along the main highway connecting Les Cayes and Jérémie. Flagged landslides may pose a particular hazard to people and structures and may benefit from additional study and monitoring. The western part of the study area lacked sufficient high-resolution imagery, so smaller landslide dams and channel obstructions may not have been fully identified or mapped. N, north; W, west. 4 Landslides Triggered by the August 14, 2021, Magnitude 7.2 Nippes, Haiti, Earthquake cases, when using poorly orthorectified images, we adjusted the location using the high-resolution DEM. For one of our more poorly orthorectified images, the root mean square error was calculated to be 45 m. This error is not representa - tive of all images used, but it provides an upper limit on the positional accuracy of our landslide mapping. As there was a large quantity of images utilized in our rapid mapping effort, a formal and systematic assessment on the positional accuracy of the data has yet to be completed. To determine the potential for human and infrastruc - ture effects, we referenced a grid of population data from the Facebook Connectivity Lab and Center for International Earth Science Information Network (2016) and OpenStreetMap (2021) . The OpenStreetMap layer displays the locations of roads, rivers, and buildings. Specific hazards identified in our study include landslide dams and roads undercut or covered by landslide debris. We flagged landslides that appeared to present an immediate hazard to people or structures. Detailed descriptions of these flagged features and locations can be found in table 1 . Corresponding satellite images of those flagged features can be seen in figures 3 – 7 . Each figure contains flagged landslides from the same general geographic region. The corresponding details in the table for each feature can be referenced using the figure number column in table 1 . The inventory described in this report includes 4,893 land - slides. The inventory remains preliminary, however, because it has not been thoroughly reviewed and high-resolution imagery remains unavailable in some areas. Additionally, there are a few localized areas in our mapping area that did not have cloud-free imagery. Coseismic Landslides The most intense landsliding occurred at the western end of the fault, where the terrain is most rugged, especially in the Pic Macaya National Park ( fig. 1 ). Areas toward which the fault rupture is directed can experience a directivity pulse of higher ground motions (for example, Somerville and others, 1997 ) and therefore may be an additional factor explaining the high landslide concentration in the western end of the fault. However, landslides occurred along the entire length of the rupture, especially along steep channels and road cuts. A majority (95 percent) of the mapped landslides were trig - gered in calcareous geologic units, based on the geologic map from the Bureau des Mines et de l’Énergie (2005), whereas only 2.8 percent were triggered in alluvium and 2.1 percent in volcanic units. Most landslides were in remote areas, although many were close to small human settlements. The green dots in figure 1 indicate landslides that have an estimated population of more than 50 people within a 200-m radius. This analysis serves as a proxy for where effects to people were most likely to have occurred. We cannot discern the effects to people from landslides in these locations using satellite imagery alone, but landslide fatalities were reported by the media ( Fox, 2021 ; Washington Post, 2021). Many roads were blocked by landslides, which hindered travel and the movement of humanitarian aid. Figure 2 shows some of the landslides likely to have affected roads, based on satellite imagery analysis. We noted 292 landslide dams that may have blocked or partially obstructed river channels as well ( fig. 2 ), although in many cases interpretation of satel - lite imagery indicates water has been able to flow through or around these obstructions. We discuss these potential landslide dams in detail in the “Ongoing Hazards” section. Simple models based on global data indicate that an M 7.2 crustal earthquake might trigger 5,000 to 11,000 landslides ( Keefer, 2002 ; Malamud and others, 2004 ); our inventory is at the lower end of that range. However, these global estimates depend on the shaking distribution details and the terrain susceptibility. Although it affected a different part of Haiti, the August 2021 earthquake was in terrain similar to the M 7.0 earthquake that occurred in Haiti on January 12, 2010 ( https:// earthquake .usgs.gov/ earthquakes/ eventpage/ usp000h60h/ executive ). Both were shallow crustal earthquakes having a combination of left-lateral strike-slip and reverse faulting, although the 2021 earthquake had a stronger reverse compo - nent than the 2010 earthquake. During the initial field recon - naissance period, 4,000 to 5,000 landslides were estimated to have been triggered by the 2010 earthquake ( Jibson and Harp, 2011 ). This was revealed to be an underestimate because 23,000 landslides were later mapped using high-resolution satellite and aerial imagery ( Harp and others, 2016 ). The landslides triggered by the 2010 earthquake were observed to have occurred primarily in steep drainages along rivers and within calcareous geologic units ( Harp and others, 2016 ). This correlation is similar to what we observed for the 2021 event. Landslide dams and increased sedimentation also were observed after the 2010 event ( Jibson and Harp, 2011 ; Harp and others, 2016 ). Coseismic Landslides 5 Table 1. Notable landslide dams and road obstructions after the 2021 Nippes, Haiti, earthquake. [Notable landslide dams and road obstructions are shown by identification numbers that correspond to point features within the associated inventory available ( Martinez and others, 2021 ). These notable features are also shown in figures 3 – 7 of this report. In some instances, quality of imagery used to display these features is limited by data availability. Coordinate locations correspond to the approximate location of flagged features. For the exact location of specific landslides, refer to Martinez and others (2021) . Communes are a third-level administrative boundary in Haiti. Because of mapping uncertainty, reported dis - tances in the table are approximate. km, kilometer; m, meter; N, north; no., number; RN-7, route Nationale 7; W, west] ID no. Coordinates Commune Description Threat Figure no. D2 D3 73.8475146°W 18.3767446°N Camp-Perrin Landslide dams blocking river; water is pooling. These landslide dams are upstream (0.2–0.4 km) from a popu - lated area with several structures adjacent to the river. 3 A D4 D5 D6 D12 D13 73.8476736°W 18.3799054°N Camp-Perrin Landslide dams with water pooling present. These landslide dams are upstream (0.8 km) from a populated area with several structures adjacent to the river. 3 A R1 73.8788310°W 18.3703507°N Camp-Perrin A series of landslides along main road, RN-7, that initially blocked this key route after the earthquake. It has since been cleared (as observed in imagery), but material will likely continue to move downslope at this location. This is a main road that connects Les Cayes and Jérémie and provides access to interior communities. 3 B R7 73.8387131°W 18.3719796°N Camp-Perrin Potentially deep landslide caused severe damage to a road in a settled area. This poses an ongoing hazard to the road and access may be limited in this area. 3 C D10 D11 73.8309072°W 18.3859385°N Camp-Perrin Two landslide dams blocked a drainage that appeared dry at the time of the image, but a small amount of pooled water is visible northeast of the easternmost dam. These landslide dams are 3.5-km upstream from a populated area and structures that are adjacent to river floodplain. 3 D D27 73.8495048°W 18.3369706°N Camp-Perrin Landslide dam with visible pooling. Immediately upstream (0.05 km) from a populated area and structures. This dam is of high concern because of its proxim - ity to structures. 3 E D28 D29 73.8227571°W 18.3359879°N Camp-Perrin Landside dam with visible pooling. This landslide dam is directly adjacent to a populated area and several structures. 3 F D24 73.8996369°W 18.4269625°N Pestel Landslide dam blocking 450 m of the river channel. Pool is about 300 m long and appears to be growing in recent imagery. Scattered settlements downstream and along the river. River drains into a closed basin or maybe a karst cavern. Adjacent to RN-7, so there is likely awareness of the growing pool. 4 A D39 D40 73.9637699°W 18.3832639°N Beaumont Landside dams with visible pooling. No densely populated areas or structures are downstream from these dams. 4 B D22 73.9681267°W 18.3697023°N Chantal Landslide dams; unknown if they are completely or partially blocking river. No populated area or structures are downstream from these dams. 4 C D18 D19 74.0443117°W 18.4109764°N Roseaux Landslide dams with pooling visible. No populated area or structures are downstream from these dams. 4 D 6 Landslides Triggered by the August 14, 2021, Magnitude 7.2 Nippes, Haiti, Earthquake Table 1. Notable landslide dams and road obstructions after the 2021 Nippes, Haiti, earthquake.—Continued [Notable landslide dams and road obstructions are shown by identification numbers that correspond to point features within the associated inventory available ( Martinez and others, 2021 ). These notable features are also shown in figures 3 – 7 of this report. In some instances, quality of imagery used to display these features is limited by data availability. Coordinate locations correspond to the approximate location of flagged features. For the exact location of specific landslides, refer to Martinez and others (2021) . Communes are a third-level administrative boundary in Haiti. Because of mapping uncertainty, reported dis - tances in the table are approximate. km, kilometer; m, meter; N, north; no., number; RN-7, route Nationale 7; W, west] ID no. Coordinates Commune Description Threat Figure no. D8 73.7247343°W 18.3867478°N Maniche Landslide dam with no pooling currently visible; water is not clearly visible in the channel. This landslide dam is 0.7-km upstream from a populated area and structures that are adjacent to river floodplain. A road parallels the river downstream. 5 A D9 73.7662063°W 18.3925709°N Maniche Landslide dam with no pooling currently visible, but no water is visible in the channel at the time of the image. Landslide is large but is close to the top of its tributary, so less area can contribute water than for some other dams. This landslide dam is 2.6-km upstream from a populated area and structures that are adjacent to river floodplain. 5 B D14 73.7512845°W 18.4118467°N Maniche Landslide dam with no pooling currently visible; chan - nel dry at time of the image. This landside dam is 1.6-km upstream from a populated area and structures that are adjacent to river floodplain. 5 C D16 D17 73.8011201°W 18.3864305°N Maniche Landslide dams with pooling visible behind the larger dam. This landslide dam is directly adjacent to a populated area and several structures. More populated regions are downstream. Roads are adjacent to and intersect the river. 5 D R23 73.7172863°W 18.3685561°N Maniche Partial landslide dam adjacent to road and river. Adjacent to road, which presents an ongoing road hazard. Upstream (1.6 km) from a populated area adjacent to river. 5 E D21 73.5362199°W 18.3865591°N L’Asile Possible deep landside damming a stream with visible pooling. This landside dam is 3.5-km upstream from populated areas and structures that are adjacent to Grand Rivière de Nippes floodplain. 6 A D25 73.5479989°W 18.3475403°N L’Asile Landslide dam; unknown if the dam is completely or partially blocking river channel. Upstream (1.6–2 km) from clusters of structures. 6 B D37 73.4468978°W 18.3712835°N L’Asile Landslide dam; unknown if the dam is completely or partially blocking river, but some pooling is visible. Directly upstream from roads (0.4–0.7 km) that intersect river and upstream (1.2 km) from populated areas with structures adjacent to river. 6 C D41 73.5263153°W 18.3857851°N L’Asile Landside dam with visible pooling but not complete restriction of flow. Upstream (3 km) from clusters of structures. 6 D R42 73.4908007°W 18.3811946°N L’Asile Potential road damage from landslide; would need higher resolution imagery to confirm. Potential ongoing road hazard. 6 E D26 73.6485411°W 18.4249629°N Cavaillon Landslide dam; unknown if the dam is completely or partially blocking river channel. Upstream (0.6 km) from clusters of structures and a road. 7 A D30 D31 D32 73.5438633°W 18.3318873°N Saint Louis du Sud Landslide dams; unknown if dams are completely or partially blocking river channel. Upstream (0.7 km) from a cluster of structures. 7 B Coseismic Landslides 7 Table 1. Notable landslide dams and road obstructions after the 2021 Nippes, Haiti, earthquake.—Continued [Notable landslide dams and road obstructions are shown by identification numbers that correspond to point features within the associated inventory available ( Martinez and others, 2021 ). These notable features are also shown in figures 3 – 7 of this report. In some instances, quality of imagery used to display these features is limited by data availability. Coordinate locations correspond to the approximate location of flagged features. For the exact location of specific landslides, refer to Martinez and others (2021) . Communes are a third-level administrative boundary in Haiti. Because of mapping uncertainty, reported dis - tances in the table are approximate. km, kilometer; m, meter; N, north; no., number; RN-7, route Nationale 7; W, west] ID no. Coordinates Commune Description Threat Figure no. D33 D34 D35 73.6196799° W 18.3886041° N Cavaillon Landside dams with visible pooling. Upstream (3.5 km) from clusters of structures and a road. 7 C D36 73.6237611° W 18.3887233° N Cavaillon Landside dam with visible pooling. Upstream (2 km) from clusters of structures and a road. 7 D D38 73.6848976° W 18.4241081° N Baradères Landslide dam; unknown if the dam is completely or partially blocking river. Upstream (1.4 km) from densely populated areas and structures. Also upstream from roads that are adjacent to and intersect the river channel farther downstream. 7 E 8 Landslides Triggered by the August 14, 2021, Magnitude 7.2 Nippes, Haiti, Earthquake A D E F B C Pooling water Pooling water Pooling water Pooling water Landslide dams Landslide dams Landslide dams Landslide dam Landslide dams Pooling water N N N N N N Image © 2021 CNES/ Airbus Imagery Date: 08/27/2021 Image © 2021 CNES/ Airbus Imagery Date: 08/27/2021 Image © 2021 CNES/ Airbus Imagery Date: 08/27/2021 Image © 2021 CNES/ Airbus Imagery Date: 08/27/2021 Image © 2021 CNES/ Airbus Imagery Date: 08/27/2021 Image © 2021 CNES/ Airbus Imagery Date: 08/27/2021 0 400 METERS 200 0 600 1,200 FEET 0 300 METERS 100 200 0 300 600 900 FEET 0 100 METERS 50 0 150 300 FEET 0 300 METERS 100 200 0 300 600 900 FEET 0 100 METERS 50 0 150 300 FEET 0 150 METERS 100 50 0 300 150 450 FEET Figure 3. Flagged landslide features in Camp-Perrin commune, identified from satellite imagery after the 2021 Nippes, Haiti, earthquake. Refer to table 1 for coordinates to locate features. A , Seven landslide dams along a river bank and upstream (0.2–0.8 kilometers [km]) from a populated area with several structures adjacent to the river. Landslide dams resulted in two pools of water. River is flowing to the south. B , A series of landslides along main road Route Nationale 7 (RN-7) that initially blocked this route after the earthquake. C , A potentially deep landslide (sliding surface of the landslide is several meters below the ground surface) that has caused severe damage to a road in a settled area. This landslide poses an ongoing hazard to the road; access may be limited in this area. D , Two landslide dams blocking a drainage that appeared dry at the time of the image. A small amount of pooled water is present to the northeast of the easternmost dam. River is flowing to the southwest. These landslide dams are 3.5-km upstream from a populated area and structures that are adjacent to river floodplain. E , Landslide dam with visible pooling immediately upstream (0.05 km) from a populated area and structures; dam is of high concern because of proximity to structures. River is flowing to the south. F , Landslide dam with visible pooling directly adjacent to a populated area and several structures. River is flowing to the north. N, north; CNES, Centre National d`études Spatiales. Coseismic Landslides 9 Image © 2021 DigitalGlobeNextView License Imagery Date: 10/10/2021 Universal Transverse Mercator projection Zone 18N World Geodetic System of 1984 Image © 2021 DigitalGlobeNextView License Imagery Date: 10/10/2021 Universal Transverse Mercator projection Zone 18N World Geodetic System of 1984 HM0476-18-C-0044, © 2021, Planet Labs Inc. Imagery Date: 08/23/2021 Universal Transverse Mercator projection Zone 18N World Geodetic System of 1984 Image © 2021 DigitalGlobeNextView License Imagery Date: 10/10/2021 Universal Transverse Mercator projection Zone 18N World Geodetic System of 1984 A B C D 18°25'40" N 18°25'26" N 18°22'05" N 18°22'20" N 18°23' N 18°22'50" N 18°23'10" N 18°24'29" N 18°24'15" N 18°24'43" N 73°57'40" W 73°57'50" W 73°58' W 73°58'10" W 73°54'14" W 73°58'20" W 73°58'05" W 73°57'50" W 74°03'08" W 74°02'53" W 74°02'38" W 74°02'23" W 73°54'00" W Landslide dam Landslide dam N N N N 0 300 METERS 100 200 0 300 600 900 FEET 0 300 METERS 100 200 0 300 600 900 FEET 0 300 METERS 100 200 0 300 600 900 FEET 0 300 METERS 100 200 0 300 600 900 FEET Figure 4. Flagged landslide features in Pestel, Beaumont, Chantal, and Roseaux communes, identified from satellite imagery after the 2021 Nippes, Haiti, earthquake. Refer to table 1 for coordinates to locate features. A , Landslide dam blocking 450 meters of the river channel; pool is about 300 meters long and appears to be growing in recent imagery. There are scattered settlements downstream and along the river. River drains into a closed basin or maybe a karst cavern. This feature is adjacent to Route Nationale 7 (RN-7), so there is likely awareness of the growing pool. River is flowing to the northeast. B , Landside dams with visible pooling; no densely populated areas or structures are downstream from these dams. River is flowing to the east. C , Landslide dams are visible; unknown if dams are completely or partially blocking the river; no populated area or structures are downstream from these dams. River is flowing to the east. D , Two landslide dams with visible pooling. Feature is shown using a false color infrared image, which was used in this instance because image bands needed to create false color images are available for this area. The landslides and resultant pooling are also more easily discernible in false color particularly in cases where image resolution is low. Quality of imagery is limited by data availability. White arrows point to the dams restricting the flow of water. River is flowing to the east. N, north; W, west. 10 Landslides Triggered by the August 14, 2021, Magnitude 7.2 Nippes, Haiti, Earthquake A C E D B Pooling water Landslide dams N N N N N Image © 2021 CNES/ Airbus Imagery Date: 08/27/2021 Image © 2021 CNES/ Airbus Image © 2021 Maxar Technologies Imagery Date: 08/27/2021 Image © 2021 CNES/ Airbus Imagery Date: 08/27/2021 Image © 2021 CNES/ Airbus Imagery Date: 08/27/2021 Image © 2021 CNES/ Airbus Imagery Date: 08/27/2021 0 200 METERS 100 0 300 600 FEET 0 200 METERS 100 0 300 600 FEET 0 200 METERS 100 0 300 600 FEET 0 100 METERS 50 0 150 300 FEET 0 600 METERS 200 400 0 800 1,600 FEET Figure 5. Flagged landslide features in Maniche commune, identified from satellite imagery after the 2021 Nippes, Haiti, earthquake. Refer to table 1 for coordinates to locate features. A , Landslide dam with no pooling currently visible; water is not clearly visible in the channel; 0.7-kilometers (km) upstream from a populated area and structures that are adjacent to river floodplain; a road parallels the river downstream. B , Landslide dam with no pooling currently visible but no water visible in the channel at the time of the image. Landslide is large but is close to the top of its tributary and so less area can contribute water than for some other dams. The landslides shown here are 2.6-km upstream from a populated area and structures that are adjacent to river floodplain. Clouds obscure a portion of the imagery. C , Landslide dam with no pooling currently visible; channel dry at time of the image. This landside dam is 1.6-km upstream from a populated area and structures that are adjacent to river floodplain. D , Two landslide dams with pooling visible behind the larger dam. River is flowing to the south. E , Partial landslide dam adjacent to river and road, which presents an ongoing hazard; upstream (1.6 km) from a populated area adjacent to river. N, north; CNES, Centre National d`études Spatiales. Coseismic Landslides 11 Image © 2021 DigitalGlobeNextView License Imagery Date: 09/08/2021 Image © 2021 DigitalGlobeNextView License Imagery Date: 09/08/2021 HM0476-18-C-0044, © 2021, Planet Labs Inc. Imagery Date: 10/25/2021 HM0476-18-C-0044, © 2021, Planet Labs Inc. Imagery Date: 09/11/2021 Image © 2021 CNES/ Airbus Imagery Date: 08/17/2021 A B 18°20'53" N 18°20'46" N 73°32'46" W 73°32'53" W 73°33'00" W 73°32'13" W 73°32'06" W C D 18°22'19" N 18°23'13" N 18°23'09" N 18°23'05" N 18°23'09" N 18°23'06" N 73°31'34" W 73°31'38" W 73°26'53" W 73°26'38" W E Landslide Floodplain boundary Potential landslide dam River channel Landslide headscarp Pooling water Pooling water Landslide dam Landslide dam N N N N N 0 200 METERS 100 0 300 600 FEET 0 200 METERS 100 0 300 600 FEET 0 120 METERS 40 80 0 100 200 300 FEET 0 80 METERS 20 40 60 0 100 200 FEET 0 200 METERS 100 0 300 600 FEET Figure 6. Flagged landslide features in L’Asile commune, identified from satellite imagery after the 2021 Nippes, Haiti, earthquake. Refer to table 1 for coordinates to locate features. Quality of imagery is limited by data availability. A , Possible deep landside damming a stream with visible pooling. This landside dam is 3.5-kilometers (km) upstream from populated areas and structures that are adjacent to Grand Rivière de Nippes floodplain. Clouds obscure part of the imagery. River is flowing to the east. B , A landslide dam; it is unknown if the dam is completely or partially blocking river channel; upstream (1.6–2 km) from clusters of structures. C , A landslide dam; it is unknown if the dam is completely or partially blocking river, but some pooling is visible. Dam is directly upstream from roads (0.4–0.7 km) that intersect river and upstream (1.2 km) from populated areas with structures adjacent to river. Feature is shown using a false color infrared image, which was used in this instance because image bands needed to create false color images are available for this area. This landslide dam and pooling are also more easily discernible in false color particularly in cases where image resolution is low. D , A landside dam with visible pooling but not complete restriction of flow. The dam is upstream (3 km) from clusters of structures. River is flowing to the east. E, Potential road damage from landslide near the landslide headscarp; need higher resolution imagery to confirm. Potential ongoing road hazard as the landslide may continue to retreat towards road. N, north; W, west. 12 Landslides Triggered by the August 14, 2021, Magnitude 7.2 Nippes, Haiti, Earthquake Image © 2021 DigitalGlobeNextView License Imagery Date: 08/23/2021 Universal Transverse Mercator projection Zone 18N World Geodetic System of 1984 Image © 2021 DigitalGlobeNextView License Imagery Date: 09/08/2021 Universal Transverse Mercator projection Zone 18N World Geodetic System of 1984 Image © 2021 DigitalGlobeNextView License Imagery Date: 09/08/2021 Universal Transverse Mercator projection Zone 18N World Geodetic System of 1984 HM0476-18-C-0044, © 2021, Planet Labs Inc. Imagery Date: 09/29/2021 Universal Transverse Mercator projection Zone 18N World Geodetic System of 1984 Image © 2021 CNES/ Airbus Imagery Date: 08/27/2021 Universal Transverse Mercator projection Zone 18N World Geodetic System of 1984 A B 18°20' N 18°19'45" N 73°32'30" W 73°32'45" W 73°38'57" W 73°38'53" W C D 18°23'17" N 18°23'20" N 18°25'30" N 18°25'26" N 18°23'21" N 18°23'18" N 73°37'24" W 73°37'27" W 73°37'30" W 73°37'12" W 73°37'16" W 73°37'08" W E Potential landslide dams Potential landslide dam Pooling water N N N N N 0 80 METERS 40 0 100 200 FEET 0 80 METERS 40 0 100 200 FEET 0 80 METERS 20 40 60 0 100 200 FEET 0 300 METERS 100 200 0 300 600 900 FEET 0 120 METERS 40 80 0 100 200 300 FEET Figure 7. Flagged landslides in Cavaillon, Saint Louis du Sud, and Baradères communes, identified from satellite imagery after the 2021 Nippes, Haiti, earthquake. Refer to table 1 for coordinates to locate features. Clouds obscure a portion of the imagery in panels A , B , and D . A, Landslide dam; unknown if the dam is completely or partially blocking the narrow river channel. The dam is upstream (0.6 kilometers [km]) from clusters of structures and a road. B , Three landslide dams; unknown if dams are completely or partially blocking river channel. Quality of imagery is limited by data availability. White arrows point to the potential landslide dams. Dams are upstream (0.7 km) from a cluster of structures. River is flowing to the west. C , Three landside dams with visible pooling. Dams are upstream (3.5 km) from clusters of structures and a road. River is flowing to the south. D , Landside dam with visible pooling. The dam is upstream (2 km) from clusters of structures and a road. River is flowing to the west. E , Landslide dam; unknown if the dam is completely or partially blocking river. The dam is upstream (1.4 km) from densely populated areas, structures, and roads that are adjacent to and intersect the river channel farther downstream. River is flowing to the north. N, north; W, west. Ongoing Hazards 13 Ongoing Hazards Hazards associated with the landslides triggered by this earthquake may pose a risk to people on the Tiburon Peninsula for several years. The following hazard assessment is based on our preliminary and rapid analysis of satellite imagery coupled with lessons learned from scientific studies of postearthquake hazards in other locations. Remotely sensed data alone can - not be used to accurately determine hazard; ideally, a remote investigation would be accompanied by field reconnaissance. This preliminary report provides information that can be used to guide future field investigations. Landslide Dams Thousands of landslides deposited debris in channels, some of which created landslide dams that impounded water ( fig. 8 ). A primary concern with these landslide dams is their potential to fail catastrophically and send a flood surge down - stream ( Fan and others, 2019 ). A flood surge, which could occur without warning, could affect people living downstream and result in the loss of life and damage to homes and infra - structure. The timing of dam failure and the magnitude of a potential flood surge are controlled by several factors, such as dam size and geometry, flow rates, and dam material charac - teristics ( Costa and Schuster, 1988 ), that cannot be determined from remotely sensed data alone. Debris dams are best assessed onsite, and therefore, we cannot provide detailed hazard or risk assessments herein. However, using high-resolution satellite imagery, we identified 292 landslides that could be restrict - ing streamflow. Most were small and had already breached or been eroded by the time imagery was collected. However, we flagged 35 of these landslides as being of potential concern because of proximity to structures, relative size of the potential dam, and potential downstream effects (in other words, people and property existing less than 4-km downstream from the landslide). Of the 35 flagged dams, we identified 20 with water pooling upstream at the time the imagery was collected (imag - ery dates ranged from August 14, 2021, to October 10, 2021). Most landslide dams fail within 10 days of formation, usually by overtopping ( Costa and Schuster, 1988 ). Over time, some dams stabilize as water erodes a new path across or through the landslide deposit, in some cases forming a natural spillway over bedrock or by channel armoring ( Costa and Schuster, 1988 ). If erosion is slow and deposits are thin, the flowing water may erode a new channel, which decreases the likelihood of a catastrophic dam failure. A concerning scenario is a large, impervious debris dam that impounds a large pool upstream and eventually catastrophically fails from overtop - ping, piping, or slope failure ( Fan and others, 2019 ). We saw no large dams of urgent concern, such as those with signs of rapid downcutting or piping through a large dam impound - ing substantial amounts of water. However, field verification would be necessary to assess this hazard more accurately because of the limitations of satellite imagery for making such assessments. We include details of the landslide dams flagged as being of concern in table 1 . Another potential long-term concern is that the imagery indicates that many channels into which numerous landslides deposited debris had no flowing water at the time the imagery was collected. This indicates possible unknown dams could start to impound water follow - ing substantial rainfall. Landslide Hazards to Roads Continued landslide activity adjacent to roads is likely to occur where destabilized debris or areas of cracking are present above or below the roadway. Continued landslides are likely during or after periods of rainfall or earthquake aftershocks. Numerous areas of minor rockfall along roads throughout the affected region may continue to affect roads ( fig. 2 ). The landslide inventory probably underrepresents landslides affecting roads because steep road cuts and more subtle road damage are difficult to determine in satellite imagery. The current area of greatest concern is a mountain pass along Route Nationale 7 (RN-7), the main highway con - necting Les Cayes and Jérémie, where a series of landslides blocked the road (see R1 in table 1 , fig. 3 B ). The road has been cleared of landslide debris (as of August 22, 2021, imagery), but substantial debris remains on the slopes above the road. Destabilized material is likely to ravel onto the road; after - shocks, rainfall, excavation, and vibrations from passing traffic could accelerate the process. Subsequent larger landslides are also possible. Increased Landslide Activity Based on global studies of past earthquakes summarized by Fan and others (2019) , an increase in landslide activity on the Tiburon Peninsula is likely for several years. The increase in expected landsliding relative to pre-earthquake activity is from, in part, the earthquake shaking that opened fractures that weakened rock and facilitated increased water infiltration. This slope damage and water infiltration destabilizes slopes and thus increases the likelihood of more landslides. Also, land - slide debris deposited on steep slopes during the earthquake could be remobilized. However, the number of landslides in this postearthquake period will likely be far fewer than the number that were triggered by the earthquake. Debris flows, not commonly triggered directly by earth - quakes, are likely to pose a greater hazard in coming years, as they can mobilize the landslide debris that was deposited in channels. Debris flows are destructive flows of rock, soil, and water that can travel down steep channels for long distances at high speed and generally are triggered by intense rainfall. Debris flows ca