When I worked in Oregon, the geologists and soil scientists typically identified the unstable land types and materials with this potential. We tried to avoid crossing these areas with roads, altering drainage or slope supports with cut slopes and fill materials. When working short term in Puerto Rico, the most active instability was in Rio Icacos, which if memory serves me was weathered granitics. Besides rainfall, anything that alters surface or subsurface flow patterns, reduces root strength and transpiration such as through clearcutting or severe wildfires in defined sensitive landforms is subject to added risk. In Researchgate, I uploaded the paper Watershed Restoration after Calamity, that included some of the indicators we used to identify instability such as jack strawed trees (leaning every which way) and pistol butted trees. Infrequently, cracks in the soil or cracks in fill materials, or some minor slumping signal warnings of instability and potential failure. One of my early papers on Flood Frequency and Risk in Forest Management discussed issues with infrequent road drainage contributing to landslides. And the aggradation of streams in unstable terrain, can also work to undercut slopes in steep terrain, increasing risk for activating unstable slopes by weakening toe slope. The faults, strike and dip of subsurface geologic types and contact zones with bedrock or more competent materials can also be contributory. Finding and evaluating underground concentrations of water coincident with unstable areas were sometimes drained to the surface with directional drilling with perforated pipe in Oregon by geologists. Perhaps identifying some of this other criteria and adjusting inventory criteria, BMPs or management approach will help prevent or at least warn of high risk landforms. In my early career we used primarily aerial photo pairs and field reconnaissance, but you might consider LiDAR as a helpful tool along with GIS as ArcMap in identifying and perhaps classifying unstable landforms, surface anomalies, areas with tipping or jackstrawed trees, etc.

Dear Mr. William F. Hansen, I appreciate very much your prompt and comprehensive reply. I will take into account your criteria. In my question, I am also referring in particular to values ​​of rainfall intensity from which the possibility of slopes slides is considered by early warning systems. In my country (Cuba) I don´t know that these values ​​exist, so I begin to work on the analysis of slope stability under the effect of intense rains, under foreign criteria. I consider this a topic of great interest, due to the influence of climate change and the need to protect hydraulic works such as earth dams.

I appreciate the desire to secure this guidance. My concern is that this amount in near saturated conditions is apt to vary with the situation (geology, soils, slopes, underlying features or bedrock, vegetation type and soil rooting depth, density and strength of roots, etc.). Certainly, rainfall amount and intensity are factors to consider, and the Doppler and other tools interfaced unstable area locations in. GIS may help develop early warning or evacuation guidance.

Yoermes, te recomiendo q busquew informacion sobre la velocidad terminal de las gotas de lluvia al impactar el suelo, lq cual depende del diametro de la gota y puede correlacionarse con la intensidad de ls lluvia..esto influye en la erosion del suelo y por tanto en su estabilidad. Esto puede ser abordado empiricamente en modelos fisicos. Espero te sea util mi comentario.

sl2. Yoel

Gracias, estimado amigo Yoel Martinez Gonzalez , tomaré en cuenta tus recomendaciones. Sl2!

In our group we worked on similar questions in Germany and Austria, where landslides are frequently developed in moisture-sensitive hillslope sediments, which are widespread within the Quaternary cover bed complex. In the context of your question we carried out a soil moisture simulation, which was performed on a monthly basis by means of a coupled single-layer soil water balance model.

Here some suggestions of papers dealing with this problem:

Damm, B., Terhorst, B., Ottner, F. (2013): Geotechnical Properties of Periglacial Cover Beds. Developments in Sedimentology 66:153-170 (full text on researchgate)

Klose, M., Damm, B., Gerold, G. (2012): Analysis of Landslide Activity and Soil Moisture in Hillslope Sediments Using Landslide Database and Soil Water Balance Model. GeoÖko 33:204–231 (full text on researchgate)

Damm, B., Terhorst, B. (2010): A model of slope formation related to landslide activity in the Eastern Prealps, Austria. Geomorphology 122(3):338-350. (full text on researchgate)

Best wishes,

Bodo Damm

Thank you, Mr. Damm. I will look for and study the documents that you recommend. Best regards.

Yoermes

You may want to check the USGS Circular 1283 USGS-NOAA Debris Flow Warning System,

https://pubs.er.usgs.gov/publication/cir128

Some of the assumptions in that report have been updated, so I am sure there will be newer documents by the USGS which may focus more on slope stability rather than the more specific Debris Flow in recently burned areas problem. This document may help in providing further references

Chapter Evaluating a Slope-Stability Model for Shallow Rain-Induced ...

Dear Yoermes Glez Haramboure,

please excuse the delay. I will immediately send you the paper of Damm, B., Terhorst, B., Ottner, F. (2013)

Best wishes,

B. Damm

Sorry for being late to this discussion.

There are many thresholds for the forecasting of landslides and you can find a comprehensive overview here: http://rainfallthresholds.irpi.cnr.it/

I highly disagree to consider some published values (the example of Medellin where I live is not trustable) as applicable to another territory. Not even for Medellin we should adopt those values. Here we do not have a regional landslide early warning system even though SIATA has tried to do some things.