Topography, which is a major land surface characteristic constituting a key pre-condition/factor in landslide occurrence, needs to be further investigated to guide planning and risk management. A watch means that landslide-activity will be possible, but is not imminent. This dynamic tectonic environment has created a spectacular landscape of rugged mountains and steep-walled valleys that compose much of the regions scenic beauty. Many human-caused landslides can be avoided or mitigated. Consult a geotechnical expert (a registered professional engineer with soils engineering expertise) for advice on reducing additional landslide problems and risks. 5, 6 and Table 2 the moderately steep slopes (15 o - 25o) had a higher FR (1.26) implying landslides were more frequent and therefore suggesting this range as a threshold. This study set out to investigate the topographic influence on the pattern and spatio-temporal distribution of landslides, and implications on risk management in the selected upper catchment of R. Manafwa. Though the area has few weather stations with longtime consistent rainfall recordings, evidence of increased rainfall frequency was observed in 2010 and 2011 by Bamutaze (2011). Environ Geol 46:1123-1133. https://doi.org/10.1007/s00254-004-1116-y. Afr J Agr Res 6:718, Knapen A, Kitutu MG, Poesen J, Breugelmans W, Deckers J, Muwanga A (2006) Landslides in a densely populated county at the footslopes of mount Elgon (Uganda): characteristics and causal factors. A lock () or https:// means youve safely connected to the .gov website. More precisely the landslide inventory data from the field and literature totaling to 284 records was imported into Arc GIS 10.5 for analysis of the landslide distribution and their characteristics with respect to geomorphometric parameters (slope, aspect, altitude, plan curvature). The USGS uses cutting edge technologies to investigate and forecast landslides and other natural hazards. Due to high population pressure there is limited land left uncultivated even on fragile slopes. contains too much water. The data was analysed using Arc GIS 10.5 and Frequency Ratio model. 2019) and thus steeper slopes are more prone. The hillslope angle was measured using a clinometer while the width, depth (at head scarp) and length of the scars was determined by a measuring tape (100m). What are Owing to improvements in video technology over the years, the quality of footage from recent experiments generally exceeds that from earlier experiments.Use the list below to access the individual videos, which are mostly grouped by date and subject matte, Landslides occur and can cause damage in all 50 States. Mountainous areas are vulnerable to mass movements due to preparatory/conditional and triggering causal factors. Furthermore, ashen debris flows caused by Regmi et al. 2011). Overall landslides were repetitive, that is majorly limited to depressions (hollows) and plan curvature on or in close proximity of old scars. (2004) and Broothaerts et al. Mining operations that use blasting techniques often cause other areas that These landslides, in turn, are often triggered by earthquakes. volume7, Articlenumber:27 (2020) CATENA 90:3646. Most landslides are caused by multiple factors that act together to destabilize the slope. Therefore, strategies designed to mitigate risks due to slope failures should not ignore topographic attributes (slope angle, curvature) besides ensuring safe disposal of surface runoff and enhancing green solutions for such areas with high fragility. It is largely underlain by the basement complex and volcanic rocks (conglomerates and agglomerates) with isolated plugs and dikes such as Nusu. will succumb to the forces of gravity. Comput Geosci 30(2004):429443, Claessens L, Knapen A, Kitutu MG, Poesen J, Deckers JA (2007) Modelling landslide hazard, soil redistribution and sediment yield of landslides on the Ugandan footslopes of Mount Elgon. The relationship between landslides and topographic conditioning factors was analysed using the Frequency Ratio model. Elgon. Ecological restoration of previous scars, be it on lower or mid-upper slopes, is required in order to enhance the slope stability. Special Report, Transp Res Board 247:3675, Dahl MPJ, Mortensen LE, Jensen NH, Veihe A (2011) Magnitudefrequency characteristics and preparatory factors for spatial debris-slide distribution in the northern Faroe Islands. There have been also raised concerns about the consequences as echoed in the government policy on Disaster Preparedness and Management of 2011. Geoenvironmental Disasters When sloped areas become Distribution of landslides on varied topography (a) debris flow in Bunamwamba village (b) Earth flow in Buwali village (c) soil slips in forest (d) complex slide/flow (e) Complex slides on two opposite hillslopes plan and hollow curvature slope in Bunamwamba and Buwali villages. they are driven by gravity.". CATENA 55(2004):163181, Giuseppe F, Simoni S, Godt JW, Lu N, Rigon R (2016) Geomorphological control on variably saturated hillslope hydrology and slope instability. It was prepared by evaluating, 12201 Sunrise Valley Drive Reston, VA 20192, Region 2: South Atlantic-Gulf (Includes Puerto Rico and the U.S. Virgin Islands), Region 12: Pacific Islands (American Samoa, Hawaii, Guam, Commonwealth of the Northern Mariana Islands), The Landslide Handbook - A Guide to Understanding Landslides. Something went wrong while submitting the form. They can also result from the eruption or collapse of island or coastal volcanoes and from giant landslides on marine margins. These are further subdivided by the type of geologic material (bedrock, debris, or earth). Flooding or additional slides may occur after a landslide or mudflow. Thus, overall there is still lack of consensus on the topographic factors underpinning landslide distribution. The FR is the ratio of landslides in a desired class as a percentage of all landslides to the area of the class as a percentage of the entire map. https://doi.org/10.1007/s10346-011-0267-7. 3. This finding is, however, in contrast to Borgomeo et al. What was the largest landslide in the United States? Clear Cutting: Method of 2019). Correspondence to Zhuang et al. Most slope failures were initiated on mid to upper slope positions in either new or old scars. (2015) on lower slope gradients, the density of landslides is low because the terrain is gentle and covered with thick colluvium and/or residual soils which require higher water levels to initiate slope failures. These terrain aspects correspond also to the direction of rainfall in the area as reported by the local population interviewed. Settlements built in the pathways of landslides on slopes is dangerous due to associated uncertainties and therefore inhabitants should be compelled to relocate to safer areas in nearby places. Oops! A trickle of flowing mud may precede a larger flow. Check for injured or trapped people near the affected area, if it is possible to do so without entering the path of the landslide or mudflow. Some runout depositions of large slides ended in streams thus undermining water quality. Excessive water is thought to be one of the most common triggers for landslides. This is also when major slope failures occur on fragile slopes. A field survey was undertaken in the sub catchment aimed at mapping all the recent and historical scars of the landslides. Geomorphology 188(2013):311, Davies TC (1996) Landslide research in Kenya. In this study we focused on how the distribution of landslides are shaped by the topographic attributes basing on a case study of the upper Manafwa catchment on the slopes of Mt. CDC is not responsible for Section 508 compliance (accessibility) on other federal or private website. Landslide frequency distribution against (a) Slope angle (b) Slope aspect (c)Altitude (e) plancurvature, (d) Profile curvature and (f) Topographic roughness index. To harmonize this data, all conditioning factors were converted from pixel count to area in Km2 using the equations: e=1000m, a conversion metric unit of meters to kilometers based on the metric conversion table where 1000m=1km and the vice versa (Taylor 1995). SN, was in charge of data capture and GIS analysis. In general, the altitude of the area lies within a range of 1200m to 2900m above sea level. This is largely attributed to increasing rainfall and therefore soil moisture with altitude. PubMedGoogle Scholar. A close scrutiny of the scars and depletion zones were made to ensure accurate mapping. Generally classified as mass movements of Seismic activities have always been a main cause of landslides throughout Google Scholar, Monsieurs E, Kirschbaum DB, Thiery W, van Lipzig N, Kervyn M, Demoulin A Jacobs L, Kervyn F, Dewitte O (2017) Constraints on landslide-climate research imposed by the reality of fieldwork in Central Africa. A careful selection of trees including those with deep and strong tensile roots is paramount. Shallow slides mainly debris flows and debris slides were predominant. 7 (a-d in plan curvature and hollows). Department of Environmental Management, Makerere University, P.O Box 7062, Kampala, Uganda, You can also search for this author in Due to poor memory and lack of proper formal recordings, it is not possible to present a comprehensive account on diurnal variations of landslides in the area extending beyond a ten-year period except where linked to cultural events like circumcision. Under what circumstances do U.S. Geological Survey landslide personnel conduct field work in landslide-prone areas? One particularly destructive type of landslide is known as a lahar. Hillslope forms particularly the convex shaped (hollows) should be used cautiously since they are susceptible to land sliding. The study area was dominated by moderately steep slopes occupying 54.51km2, which is ~32% of the catchment area. University of Colorado Natural Hazards Centerexternal iconprovides a resources page of landslide-related websites. Landslides are caused by disturbances in the natural stability of a slope. The worldwide death toll per year due to landslides is in the thousands. The data set used/not used for analysis in this paper are available on request from the corresponding author. Provided by the Springer Nature SharedIt content-sharing initiative. The results reveal that the landslides are generally unevenly distributed over the study area. The retreat of Barry Glacier has contributed to the destabilization of slopes in Barry Arm, creating the possibility that a landslide could rapidly enter the fjord and trigger a tsunami.The U.S. Geological Survey (USGS) recently released a report documenting potential tsunami wave heights in the event of a large, fast-moving landslide at the Barry Arm fiord near Prince William Sound, Alaska (Barnh, Lahar, an Indonesian word for volcanic mudflow, is a mixture of water, mud, and volcanic rock flowing swiftly along a channel draining a volcano. Concerted efforts should also involve collaboration of farming communities along the entire hillslopes and catchment as a whole. Monitoring can detect when hillslopes are primed for sliding and can provide early indications of rapid, catastrophic movement. Clear cutting Lahars can form during or after eruptions, or even during periods of inactivity. Studies by Nseka et al. The Landslide Handbook A Guide to Understanding Landslides. 2012). Without the aid of mechanical root support the soil simply runs off when it Many homes were left at great risk on the affected slopes. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. (2012) among others have emphasized the role of investigating topographic influence. Article Elgon, eastern Uganda. The largest subaerial (on land) landslide in Earth's recorded history was connected with the 1980 eruption of Mount St. Helens volcano in Washington state, USA. The Oso (SR 530) Landslide in Washington - Five Years Later. She writes about Earth science and nature conservation for EarthSky. certain areas due to human activity. (2015) observed higher frequency of landslides at higher elevation than lower elevation. http://www.ga.gov.au "they are the results The old scars were, however, difficult to classify owing to the blurred shapes as a result of erosion and vegetation grown. Your submission has been received! A database was constructed based on landslide inventory from field surveys supplemented by desk research. As explained above, quite a number of failures were observed on mid to upper slope positions either coinciding with or close to the previous scars. Eastern Uganda. 6 and photographs in Fig. This is particularly more so for the encircled (red) areas in southern, mid-western and north western portion of the sub catchment. 2012), and South Africa (Gupta 2001) and Uganda (Mertens et al. The portion of the forest adjacent the boundary was disturbed in the past due to deforestation for agricultural purposes but is now under recovery. These factors include both natural events such as geological weathering and erosion and human-related activities such as deforestation and changes made to the flow of groundwater. of the failure of the soil and rock materials that make up the hill-slope and These landslides are called submarine landslides. https://doi.org/10.1007/s10346-012-0380-2, Regmi NR, Walter JI (2019) Detailed mapping of shallow landslides in eastern Oklahoma and western Arkansas and potential trigge, Geomorphology, https://doi.org/10.1016/j.geomorph.2019.05.026, Silalahi FES, Arifianti PY, Hidayat F (2019) Landslide susceptibility assessment using frequency ratio model in Bogor, West Java, Indonesia. Table2 presents a summary of the analyses. Landslides can be initiated in slopes already on the verge of movement by rainfall, snowmelt, changes in water level, stream erosion, changes in ground water, earthquakes, volcanic activity, disturbance by human activities, or any combination of these factors. Deep roots contribute to anchoring top and sub soils with regolith. Mudslides usually start on steep slopes and can be activated by natural disasters. According to Giuseppe et al. (2011) such local scale studies can also effectively inform strategies for landslide risk reduction. Prior to the slide, the Oso area which is about 55 miles northeast of Seattle had had heavy rainfall during the previous 45 days, up to 261 percent of normal, by some sources. Getting out of the path of a debris flow is your best protection. The upper part of the sub catchment is under forest cover and the management of the Uganda Wildlife Authority.

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