Landslides are relatively frequent in Ottawa due to the presence of sensitive marine clays (Leda clay or Champlain Sea clay), and the presence of natural or climatic triggers such as rainfall or snowmelt. A geographic information system (GIS) based modeling tool has been developed to assess and predict climate (rainfall and snowmelt)-induced landslides in the sensitive marine clays of the Ottawa region. The Transient Rainfall Infiltration and Grid-based Regional Slope-Stability (TRIGRS) model is used in a GIS framework to investigate the influence of rainfall and snowmelt on shallow landslides through the Ottawa region, with respect to time and location. First, the GIS and TRIGRS models are combined to assess landslide susceptibility with respect to rainfall. The GIS-TRIGRS approach requires topographic, geologic, hydrologic, and geotechnical information of the study area. In addition to this technical information (input data), rainfall intensity data for different durations (5 minutes, and 6, 12, 18, and 24 hours), and historical data of the regional landslides is required. This data is used to verify the locations of predicted landslide-susceptible areas with respect to historical landslide maps in the area. The generated results from the GIS-TRIGRS model were verified by comparing the predicted and historical locations of shallow landslides induced by rainfall throughout the Ottawa region. The comparison results showed a high correlation between the predicted areas of landslides and the previously reported landslides. In addition, the results also indicated that not all previous landslides in Leda clays were triggered by rainfall. The second application of the developed GIS-TRIGRS approach was used to assess and predict snowmelt-induced landslides in areas of sensitive marine clay in the Ottawa region. Similar to the first analysis, the approach requires the following input data: topographic, geologic, hydrologic, geotechnical, snowmelt intensity data for various periods (6–48 hours, 3–15 days, 25 days, and 30 days), This approach also requires data indicating the location of historical landslides in the study area. Using this data, we examine both the timing and location of shallow landslides due to snowmelt in a GIS-based framework. The developed model was validated by comparing the predicted landslide-susceptible areas to historical landslide maps in the study area. A high correlation between predicted and historical landslide location trends was obtained, confirming that the developed GIS-TRIGRS model can predict the snowmelt-induced landslide susceptibility in the sensitive marine clays relatively well. The model results reinforced the conclusion that areas with high slopes and sensitive marine clays were more prone to snowmelt-induced landslides. Finally, in a Geographic Information System (GIS) the landslide occurrence susceptibility in the Ottawa area was modeled. Results of such models are presented as maps showing landslide susceptibility in Champlain Sea clays (Leda clays) in the Ottawa area due to both rainfall and snowmelt. Various input data was collected and entered into a GIS and TRIGRS model. The main categories of such inputs are climate, topography, geology, hydrology, and geotechnical data. The rainfall and snowmelt intensity data was extracted for 24 to 48 hour periods from Environment and Climate Change Canada historical climate records. Thereafter, the factor of safety was calculated in order to determine the stability of slopes across the study area. The model assesses the effects of rainfall and snowmelt on landslide occurrence, and based on the calculated factor of safety at each pixel of the study area, the model calculates the landslide susceptibility. The results presented in this thesis will provide a geotechnical basis for making appropriate engineering decisions during slope management and land use planning in the Ottawa region.

Em função da ocorrência de desastres naturais no Brasil, instaurou-se em 2012 a Lei Federal no 12.608 de Política Nacional de Proteção e Defesa Civil, que incentiva medidas de previsão para conter desastres naturais e situações de risco. O uso de modelos matemáticos em bases físicas pode ser uma importante ferramenta no auxílio à redução das situações negativas geradas por escorregamentos, sobretudo em áreas íngremes como a Serra do Mar. O objetivo deste trabalho foi comparar cenários de suscetibilidade a escorregamentos translacionais rasos gerados pelo modelo TRIGRS na Bacia do Rio Guaxinduba (Caraguatatuba, SP) afetada por vários escorregamentos e corridas de detritos em março de 1967. Especificamente, objetivou-se gerar três cenários de suscetibilidade considerando valores da literatura, coletados in situ e distribuídos estatisticamente; caracterizar espacialmente as propriedades geotécnicas e hidrológicas do solo (coesão; densidade; espessura máxima; ângulo de atrito interno e condutividade hidráulica saturada vertical) coletadas in situ e avaliar a variação do Fator de Segurança (FS) conforme a profundidade do solo. Para isso, foram gerados três cenários utilizando-se, no primeiro, valores geotécnicos e hidrológicos disponíveis na literatura, no segundo, valores coletados dentro da bacia e no terceiro, valores geoestatisticamente distribuídos. A partir da combinação com o mapa de cicatrizes de 1967, para validação dos cenários foram utilizados os seguintes índices: (a) Concentração de Cicatrizes; (b) Potencial de Escorregamentos e (c) percentual de áreas instáveis sem cicatrizes e de áreas estáveis com cicatrizes. Os resultados dos cenários indicaram que o uso de dados geotécnicos e hidrológicos coletados in situ forneceu resultados melhores e mais representativos. Nos três cenários foi verificada uma concordância entre as cicatrizes e as áreas instáveis, mas houve uma diferença na distribuição de classes de estabilidade. Topograficamente, foram observadas maiores instabilidades em ângulos da encosta >20º, com formas retilíneas e côncavas e em classes intermediárias de área de contribuição. Geotecnicamente, foram observadas importantes relações entre a instabilidade e os valores de coesão do solo; especialmente entre os valores de 0kPa a 6kPa. Nos demais parâmetros, observou-se maior suscetibilidade nas áreas com densidade entre 17kg/m3 e 18kg/m3; espessuras de 3m; ângulos de atrito interno entre 31º e 35º e condutividade hidráulica entre 1,0x10-3m/s e 1,0x10-4m/s. Em função dos resultados obtidos, o modelo TRIGRS e a espacialização de parâmetros geotécnicos e hidrológicos podem ser utilizados pelo poder público, em suas diferentes esferas administrativas para a definição de áreas de risco e para o planejamento do uso e ocupação do solo (ex. construção de moradias e de estradas, práticas florestais, entre outros). / Due to the occurrence of natural disasters in Brazil, the National Protection and Civil Defense Policy Federal Law no. 12,608 was established in 2012, which encourages prediction measures to minimize natural disasters and risk situations. The use of mathematical models in physical basis can be an important tool in helping to reduce negative situations generated by landslides, especially in steep areas such as the Serra do Mar mountain rage. The goal of this work was to compare susceptibility scenarios to shallow landslides generated by the TRIGRS model at the Guaxinduba hydrographic basin (Caraguatatuba, SP), affected by various landslides and debris flows in March 1967. Specifically, the generation of three susceptibility scenarios was aimed, considering literature values, collected in situ and statistically distributed; to spatially characterize the geotechnical and hydrological properties of the soil (soil cohesion; soil density; soil thickness; internal friction angle and saturated hydraulic conductivity) collected in situ and evaluate the Factor of Safety (FS) according to soil depth. To achieve this, three scenarios were generated, using, in the first, geotechnical and hydrological values available in literature, in the second, values collected inside the basin and in the third, geostatistically distributed values. From the match with the 1967 map of scars, the following indexes were used to validate the scenarios: (a) Scars Concentration; (b) Potential Landslides and (c) percentage of unstable areas without scars and stable areas with scars. The results of the scenarios indicated that the use of in situ collected geotechnical and hydrological data supplied better and more representative results. In the three scenarios, a concordance between the scars and the unstable areas was verified, but there was a difference in the distribution of stability classes. Topographically, greater instabilities were observed at >20º slope angles, with slope straight and concave slope shapes, and at intermediate classes of contribution area. Geotechnically, important relations between the instability and the soil cohesion values were noted; especially between the values ranging from 0kPa to 6kPa. In the other parameters, a greater susceptibility was observed in the areas with densities between 17kg/m3 and 18kg/m3; 3m thicknesses; internal friction angles between 31º and 35º and hydraulic conductivity between 1,0x10-3m/s and 1,0x10-4m/s. According to the results, the TRIGRS model and the spatialization of geotechnical and hydrological parameters may be used by the Government, in its various administrative levels, for the definition of risk areas and to plan the land use and occupation (e.g., construction of housing and roads, forest practices, among others).

Em função da ocorrência de desastres naturais no Brasil, instaurou-se em 2012 a Lei Federal no 12.608 de Política Nacional de Proteção e Defesa Civil, que incentiva medidas de previsão para conter desastres naturais e situações de risco. O uso de modelos matemáticos em bases físicas pode ser uma importante ferramenta no auxílio à redução das situações negativas geradas por escorregamentos, sobretudo em áreas íngremes como a Serra do Mar. O objetivo deste trabalho foi comparar cenários de suscetibilidade a escorregamentos translacionais rasos gerados pelo modelo TRIGRS na Bacia do Rio Guaxinduba (Caraguatatuba, SP) afetada por vários escorregamentos e corridas de detritos em março de 1967. Especificamente, objetivou-se gerar três cenários de suscetibilidade considerando valores da literatura, coletados in situ e distribuídos estatisticamente; caracterizar espacialmente as propriedades geotécnicas e hidrológicas do solo (coesão; densidade; espessura máxima; ângulo de atrito interno e condutividade hidráulica saturada vertical) coletadas in situ e avaliar a variação do Fator de Segurança (FS) conforme a profundidade do solo. Para isso, foram gerados três cenários utilizando-se, no primeiro, valores geotécnicos e hidrológicos disponíveis na literatura, no segundo, valores coletados dentro da bacia e no terceiro, valores geoestatisticamente distribuídos. A partir da combinação com o mapa de cicatrizes de 1967, para validação dos cenários foram utilizados os seguintes índices: (a) Concentração de Cicatrizes; (b) Potencial de Escorregamentos e (c) percentual de áreas instáveis sem cicatrizes e de áreas estáveis com cicatrizes. Os resultados dos cenários indicaram que o uso de dados geotécnicos e hidrológicos coletados in situ forneceu resultados melhores e mais representativos. Nos três cenários foi verificada uma concordância entre as cicatrizes e as áreas instáveis, mas houve uma diferença na distribuição de classes de estabilidade. Topograficamente, foram observadas maiores instabilidades em ângulos da encosta >20º, com formas retilíneas e côncavas e em classes intermediárias de área de contribuição. Geotecnicamente, foram observadas importantes relações entre a instabilidade e os valores de coesão do solo; especialmente entre os valores de 0kPa a 6kPa. Nos demais parâmetros, observou-se maior suscetibilidade nas áreas com densidade entre 17kg/m3 e 18kg/m3; espessuras de 3m; ângulos de atrito interno entre 31º e 35º e condutividade hidráulica entre 1,0x10-3m/s e 1,0x10-4m/s. Em função dos resultados obtidos, o modelo TRIGRS e a espacialização de parâmetros geotécnicos e hidrológicos podem ser utilizados pelo poder público, em suas diferentes esferas administrativas para a definição de áreas de risco e para o planejamento do uso e ocupação do solo (ex. construção de moradias e de estradas, práticas florestais, entre outros). / Due to the occurrence of natural disasters in Brazil, the National Protection and Civil Defense Policy Federal Law no. 12,608 was established in 2012, which encourages prediction measures to minimize natural disasters and risk situations. The use of mathematical models in physical basis can be an important tool in helping to reduce negative situations generated by landslides, especially in steep areas such as the Serra do Mar mountain rage. The goal of this work was to compare susceptibility scenarios to shallow landslides generated by the TRIGRS model at the Guaxinduba hydrographic basin (Caraguatatuba, SP), affected by various landslides and debris flows in March 1967. Specifically, the generation of three susceptibility scenarios was aimed, considering literature values, collected in situ and statistically distributed; to spatially characterize the geotechnical and hydrological properties of the soil (soil cohesion; soil density; soil thickness; internal friction angle and saturated hydraulic conductivity) collected in situ and evaluate the Factor of Safety (FS) according to soil depth. To achieve this, three scenarios were generated, using, in the first, geotechnical and hydrological values available in literature, in the second, values collected inside the basin and in the third, geostatistically distributed values. From the match with the 1967 map of scars, the following indexes were used to validate the scenarios: (a) Scars Concentration; (b) Potential Landslides and (c) percentage of unstable areas without scars and stable areas with scars. The results of the scenarios indicated that the use of in situ collected geotechnical and hydrological data supplied better and more representative results. In the three scenarios, a concordance between the scars and the unstable areas was verified, but there was a difference in the distribution of stability classes. Topographically, greater instabilities were observed at >20º slope angles, with slope straight and concave slope shapes, and at intermediate classes of contribution area. Geotechnically, important relations between the instability and the soil cohesion values were noted; especially between the values ranging from 0kPa to 6kPa. In the other parameters, a greater susceptibility was observed in the areas with densities between 17kg/m3 and 18kg/m3; 3m thicknesses; internal friction angles between 31º and 35º and hydraulic conductivity between 1,0x10-3m/s and 1,0x10-4m/s. According to the results, the TRIGRS model and the spatialization of geotechnical and hydrological parameters may be used by the Government, in its various administrative levels, for the definition of risk areas and to plan the land use and occupation (e.g., construction of housing and roads, forest practices, among others).

The City of Ottawa is situated in an area known as the Champlain Sea, 17,000 years before present (BP) the entire area was covered with sea water. This area deposited marine clays which are known to be highly sensitive. The City of Ottawa needs to expand land use to allow for the expansion of infrastructure and housing to support its growth. This study is intended to assist the City of Ottawa’s geotechnical engineers in their decision-making by identifying future sensitive areas prone to landslides due to rainfall based on future climate model data. The project incorporates rainfall intensities from downscaled climate model data in the Transient Rainfall Infiltration and Grid-based Regional Slope-Stability (TRIGRS) model to investigate areas sensitive to landslides, then within a GIS platform, the future landslide susceptibility maps were created based on Factor of Safety (FS) values showing the areas prone to landslides. The data input for the model includes climate model data, topography, hydrogeology, geology and geophysical data obtained from a previous study. These data were prepared using ArcGIS software and converted into ascii format for TRIGRS model. The model was calibrated using historical rainfall intensities and validated by comparing to historical landslide areas. Sensitivity analysis were performed to ranges of geotechnical properties found within sensitive marine clays in the area to find the values best to create the ideal scenario, normal scenario and worst-case model scenario for the prediction. Rainfall intensities from projected climate data Intensities Duration Frequency (IDF) of 10 years and 50 years returning period and rainfall intensities of 12 hr, 24 hr, and 48 hr were selected for the model. Results from simulations find the projected climate rainfall intensity do not have impact or has minimal impact to slope stability in sensitive marine clay areas in Ottawa directly. However, higher rainfall runoff is expected from projected rainfall RCP8.5 than the RCP4.5. The infiltration rate remains constant throughout each simulation, which is the same value as the hydraulic conductivity. The time when the slope becomes unstable varies depending on initial water levels. Results from the ideal and normal scenario show no areas prone to slope failure after 48 hours of rainfall duration. However, the factor of safety decreases as the rainfall duration increases and is expected to decrease with longer rainfall durations. The worst-case scenario shows some areas prone to slope failure (FS < 1) with 2% probability of slope failure at 48 hours of rainfall duration. The distribution of these unstable areas are located along the Ottawa River, Rideau River, Carp River, Mississippi River and valleys along their tributaries, the majority of the area prone to slope instability from rainfall are in the east part of the City of Ottawa. While there are many uncertainties and limitations which contribute to the model results, this study is useful to engineers and planners in initial implementation of mitigation strategies to mitigate the damages and cost from landslides events. The susceptibility maps can also assist in decision making for planners in developing into these areas.