Landslides, river incision and environmental change: the Ruzizi gorge in the Kivu Rift

<p>The understanding of the interplay between natural and human induced factors in the occurrence of landslides remains poorly constrained in many regions, especially in tropical Africa where data-scarcity is high. In these regions where population growth is significant and causes changes in land use/cover, the need for a sustainable management of the land is on the rise. Here, we aim to unravel the occurrence of landslides in the 40 km-long Ruzizi gorge, a rapidly incising bedrock river in the Kivu Rift in Africa that has seen its landscape disturbed over the last decades by the development of the city of Bukavu (DR Congo). Careful field observations, historical aerial photographs, satellite imagery and archive analysis are combined to produce a multi-temporal inventory of 264 landslides. We show that the lithological context of the gorge and its extremely high incision rate (> 20 mm year<sup>-1</sup>) during the Holocene explains the presence of a concentration of large landslides (up to 2 km²) of undetermined age (well before the first observations of 1959) whose occurrence is purely natural. They are mostly of the slide type and do not show morphologic patterns of recent activity. The landslides that occurred during the last 60 years are flow-like shallower slope failures of smaller size (up to 0.12 km²) and tend to disappear rather quickly (sometimes within a few years) from the landscape as a result of rapid vegetation growth, land reclamation and (human-induced) soil erosion. They are primarily related to threshold slopes and precipitation plays a frequent role in their onset. However, land use/cover changes also affect their occurrence. This study provides useful information for a more accurate evaluation of the landslide hazard in the area, particularly with respect to the growth of the city of Bukavu that has developed without the consideration of naturally instable slopes. It also stresses the need and added value of building accurate landslide inventories in data-scarce regions.</p>

Enhancing the completeness of statistical landslide susceptibility modeling by integration of release and propagation zones

<p>Statistical landslide susceptibility models have been satisfactorily fulfilling the aim of predicting where future slides might happen, or more specifically, be initiated. By aiming to answer where landslides are likely to be initiated, those models mostly build upon mapped landslide release zones to create spatial predictions. The potential downslope propagation zones are usually neglected. This is a substantial limitation with regard to their applicability in the context of risk assessment in areas characterized by steep slopes. In fact, slide-type movements often evolve into flow-like movements, traveling long distances and thereby impacting also moderate and even nearly flat slopes. At this point, the integration of modeling approaches able to predict downslope landslide routes can contribute to enhance the completeness of the model.</p><p>This study aims to explore the added value of combining statistical modeling of landslide release areas with a data-driven runout model for a 54 km² catchment in the Nova Friburgo area in southern Brazil. In January 2011, a severe rainfall event in that mountainous region triggered numerous landslides, some of them evolving into hillslope debris flows affecting downslope areas. The hundreds of slides mapped after this event are here used as reference data.</p><p>The methodology consists of three steps: (a) the creation of multiple statistical landslide release susceptibility models; (b) back-analyzing the probability density functions of the angle of reach and travel distance, derived from the observed runout zones with the r.randomwalk model; (c) integration of the best performing release susceptibility model with r.randomwalk, computing the propensity of downslope regions to be affected, based on the release susceptibility and the probability density functions derived in (b).</p><p>Despite the appropriateness of purely statistical models for predicting future slide release zones, these models indeed overlook downslope propagations. The combined model, in its turn, not only succeeds in informing where landslides would initiate, but also about their downslope impact areas. The difference between the models is even more evident when analyzing how both models would predict the susceptibility for settled areas. While the release susceptibility model assigns more than 60% of this area to the low and very low susceptibility classes, the combined model predicts that actually less than 30% of this area would be assigned to the same classes. In a region where thousands of people are living, this difference might inform a large number of people and key infrastructure prone to be landslide affected. This greatly enhances the potential of landslide susceptibility models to be applied for hazard and risk management purposes also in those areas where landslides develop into hillslope debris flows.</p>

Detection Of Sliding Plane as A Disaster Mitigation Efforts In The Pengembur Village, Pujut Sub District, Central Lombok Regency

A landslide disaster is a threatening disaster every time coming of the rainy season. Landslide potency can be detected on the surface through the form of topography and vegetation and beneath the surface of the rock layers former. From the type of rock the former can be known existence of the sliding plane which is the place of the sliding material. Research has been conducted to detect the plane of slide based on the resistivity value and the shear wave speed by using geoelectric and seismic method in Pengembur village, sub district of Pujut, Central Lombok regency. The result of analysis shows that the rocks layer former in the area consist of low cohesion soil deposits, weathered clay soils, water-saturated sand, and unconsolidated sand which has a thickness (3.7 – 4.0) meters. The field of sliding plane is detected as a layer of clay with landslides potency towards the west with the translation slide type

Development of a diagnostic PD-L1 immunohistochemical assay for nivolumab therapy in urothelial carcinoma.

e14585 Background: PD-L1 IHC 28-8 pharmDx is a qualitative assay developed by Agilent Technologies for the Autostainer Link 48 platform and is based on EnVision FLEX visualization technology and monoclonal rabbit anti-PD-L1, clone 28-8 antibody. The assay has been co-developed with the immunotherapeutic agent nivolumab; initially as an aid in assessing PD-L1 expression in non-squamous non-small cell lung cancer (NSCLC) and melanoma patients. Here we describe the efforts to validate this assay for urothelial carcinoma (UC). Methods: IHC staining was performed on Autostainer Link 48 platform using an automated staining protocol stated per the assay’s instruction for use (IFU). Specimens were coverslipped and interpreted for % PD-L1 positive tumor cells. The assay was analytically validated on commercially acquired formalin-fixed, paraffin-embedded (FFPE) human UC invasive tumor specimens at ≥1% and ≥5% PD-L1 positive tumor cells expression levels. Results: A wide range of % PD-L1 positive tumor cells at all staining intensity levels have been detected. Assay in-house precision was validated for inter-operator, inter-instrument, inter-day, inter-run and intra-run as well as inter-observer and intra-observer agreement. Robustness studies evaluated the assay under multiple conditions for target retrieval pH, temperature and incubation time, slide type as well as tissue section thickness. Assay reproducibility was evaluated at three external sites by testing samples for intra-site/inter-day and inter-site agreement measures. Specimens were also evaluated by an observer at each site, with three reads for each observer to assess intra-observer and inter-observer agreement. All validation studies demonstrated agreement estimates above 85% with values for lower bound 95% confidence intervals calculated above 84%. Conclusions: Results of all conducted studies show high robustness and reproducibility of the assay on UC.