Slope Basins Research Articles

Morphometric analysis and prioritisation of watersheds for flood risk management in Wadi Easal Basin (WEB), Jordan, using geospatial technologies

AbstractMorphometric analysis and sub‐watersheds prioritisation were carried out for the Wadi Easal Basin, Jordan, which is characterised by a high topographic diversity. The total ranking method was applied to prioritise the sub‐watersheds in terms of susceptibility to flash flood. Results of morphometric analysis revealed that the study area is a fifth order drainage system with a dendritic drainage pattern and elongated shape. Prioritisation results showed that about 71% (15 out of 21 sub‐watersheds) of sub‐watersheds have high‐very high susceptibility to flooding, which forms about 64% of the total area of the basin. The main underlying morphometric parameters behind this are the high drainage density, stream frequency, high basin relief, basin slope, ruggedness number, and circulatory ratio, and the low value of basin shape. Overall, the basin has a rugged topography with steep slopes and high relief. Since the basin is ungauged, and no information about its past hydrological behaviour is present, the results of this study can be used as guidance for competent authorities to initialize flood mitigation or artificial groundwater recharge measures.

Variable In Situ Stress Orientations Across the Northern Hikurangi Subduction Margin

AbstractWe constrain orientations of the horizontal stress field from borehole image data in a transect across the Hikurangi Subduction Margin. This region experiences NW‐SE convergence and is the site of recurrent slow slip events. The direction of the horizontal maximum stress is E‐W at an active splay thrust fault near the subduction margin trench. This trend changes to NNW‐SSE in a forearc trench slope basin on the offshore accretionary wedge, and to NE‐SW in the onshore forearc. Multiple, tectonic, and geological processes, either individually or in concert, may explain this variability. The observed offshore to onshore stress rotation may reflect a change from dominantly compressional tectonics at the deformation front, to a strike‐slip and/or extensional tectonic regime closer to the Taupo Volcanic Zone, further inland. In addition, the offshore stress may be affected by topography and/or stress rotation around subducting seamounts, and/or temporal stress changes during the slow slip cycle.

Moisture Transfer Finite Element Modeling with Soil-Water Characteristic Curve-Based Parameters and its Application to Nhan Co Red Mud Basin Slope

Since the year of 2017 landslides at the red mud basins in Nhan Co alumina factory, Dak Nong province have been occurring during the rainy seasons. The change of the soil physical and mechanical parameters due to rainwater infiltration has been considered as the main factor of the slope instability. The soil cohesion and angle of internal friction depend very much on the soil moisture: soil with a lower moisture content has a higher shearing strength than that with higher moisture content. The finite element modeling of moisture transfer in unsaturated soils through the relationship between soil moisture, soil suction, unsaturated permeability and soil-moisture dispersivity is capable of accurately predicting the wetting front development. The element sizes and time steps have been selected based on detailed analysis of analytical error estimation and on the numerical simulations with different element sizes numerical simulation errors. Soil samples had been taken and the soil different suctions and corresponding soil moisture values have been determined in the laboratory. The soil water characteristic curve (SWCC) parameters (a, n and m) have been determined by the best fitting using the least squared error method. The hydraulic conductivity of the saturated soil, one of the key input parameters was also determined. The results of the application to the study area's slope has shown that the wetting front depth can be up to 8 meters for 90 days of moisture transfer due to the rainwater infiltration The wetting front depth and the length of the intermediate part of the moisture distribution curve have increased with the infiltration time. The soil moisture distribution with a depth is an essential information to have soil strength parameters for the slope stability analyses. The slope stability analysis with the soil shear strength parameters which are strictly corresponding with the moisture change would provide the most accurate and reliable slope stability results and provide more reliable slope stabilization solutions.

Geochemical discrimination of individual hornblende shards from crypto-tephra deposits intercalated in MD012422 core at continental slope basin off Shikoku and Mihama tephra at Kiyama Formation in Fukui Prefecture, using their major and trace element compositions

Geochemical discrimination of individual hornblende shards from crypto-tephra deposits intercalated in MD012422 core at continental slope basin off Shikoku and Mihama tephra at Kiyama Formation in Fukui Prefecture, using their major and trace element compositions

A hybrid SVR-PSO model to predict concentration of sediment in typical and debris floods

Since sediment concentration is an effective factor on increasing debris flood’s peak flow and damages from floods, developing new models to predict the sediment concentration of debris floods has crucial importance. In this study, a hybrid SVR-PSO model was proposed to predict the concentration of sediment in typical and debris floods, and it was examined in three basins located in Gilan, Mazandaran, and Tehran Provinces, Iran. Mean elevation and slope of the basin, the area of the basin, current day’s rainfall, the rainfall of previous days (1–3 days before flood) for all rain-gauge stations of the basins, as well as the discharge of the previous day, were used as the input variables of the model. Then, various combinations of variables were tested to assess the factors influencing the concentration of sediment in typical and debris floods in order to find the best variable combination with a high performance in predicting the concentration of sediment in the studied floods. The results showed that basin elevation, current day’s rainfall, previous day’s discharge, rainfall of the previous day, basin area, rainfall of the previous two days, basin slope, and rainfall of the previous three days were the key factors influencing the concentration of sediment in typical and debris floods, respectively. Coefficient of determination, root mean square error, and mean absolute percentage error were estimated 0.96, 0.003, and 14.38% for the proposed model at the testing phase, respectively. This implies model’s good performance for predicting the concentration of sediment in typical and debris floods so that the present model can provide reliable predictions of flood character in basins.

Eroding Cascadia—Sediment and solute transport and landscape denudation in western Oregon and northwestern California

AbstractRiverine measurements of sediment and solute transport give empirical basin-scale estimates of bed-load, suspended-sediment, and silicate-solute fluxes for 100,000 km2 of northwestern California and western Oregon. This spatially explicit sediment budget shows the multifaceted control of geology and physiography on the rates and processes of fluvial denudation. Bed-load transport is greatest for steep basins, particularly in areas underlain by the accreted Klamath terrane. Bed-load flux commonly decreases downstream as clasts convert to suspended load by breakage and attrition, particularly for softer rock types. Suspended load correlates strongly with lithology, basin slope, precipitation, and wildfire disturbance. It is highest in steep regions of soft rocks, and our estimates suggest that much of the suspended load is derived from bed-load comminution. Dissolution, measured by basin-scale silicate-solute yield, constitutes a third of regional landscape denudation. Solute yield correlates with precipitation and is proportionally greatest in low-gradient and wet basins and for high parts of the Cascade Range, where undissected Quaternary volcanic rocks soak in 2–3 m of annual precipitation. Combined, these estimates provide basin-scale erosion rates ranging from ∼50 t · km−2 · yr−1 (approximately equivalent to 0.02 mm · yr−1) for low-gradient basins such as the Willamette River to ~500 t · km−2 · yr−1 (∼0.2 mm · yr−1) for steep coastal drainages. The denudation rates determined here from modern measurements are less than those estimated by longer-term geologic assessments, suggesting episodic disturbances such as fire, flood, seismic shaking, and climate change significantly add to long-term landscape denudation.

Pure risk premium rating of debris flows based on a dynamic run-out model: a case study in Anzhou, China

Debris flow risk is growing with the current increases in landscape exploitation and extreme precipitation events associated with global warming. Insurance is an efficient approach to cope with disasters. Based on the quantitative assessment, the debris flow hazard was obtained by a dynamic run-out model (FLO-2D), and the pure risk premiums of debris flow disaster were rating in a high-risk region (Anzhou) in Sichuan, China. Simulation results indicated that disastrous debris flows would reoccur every 5 years on average under the contemporary climatic and geological conditions of the study area. The mountain region experienced a wider area affected by debris flows than plains and hills; however, its area affected by low debris flow depth (d < 0.1 m) accounts for a larger proportion (56.69% and 22.60%, respectively). The probability of sub-basins with basin slopes of 5°–10° experiencing serious debris flows was pretty close to the probability of sub-basins with slopes of 25°–35°, which are considered to be susceptible to trigger debris flows. Furthermore, for relatively flat sub-basins (slopes < 25°), the part closer to source was more susceptible to higher flow depth. Risk assessment results showed that the significant spatial difference between the distribution of debris flow risk and hazard largely linked to the distribution of at-risk element (buildings). The pure risk premium of Anzhou was rated as 0.69–25.48‰ depending on the proportion of at-risk buildings to insured buildings, which highlights the need to encourage or require more low-risk and secure buildings to participate in insurance schemes to share the debris flow risk of the entire region.

Assessment of Surface Water Resources in Case of Muger Sub Basin, Ethiopia

Water resources assessment (WRA) is the process of measuring, collecting and analysing relevant parameters on the quantity and quality of water resources for the purposes of a better development and management of water resources. The aim of this research is Assessment of Surface Water Resource in Case of Muger Sub Basin in Ethiopia. The future possible local climate variables are extracted from Abbay basin RCM and then the bias-corrected with observed meteorological variables which are then used as input to the soil and water assessment tool (SWAT) model as climate data, in addition to climate data soil data, land use land cover, slope of the sub basin and weather Generator together are used to simulate future water yield of Muger sub-basin. Soil and Water Assessment Tool (SWAT) was adopted to perform runoff simulation. The good performance of the SWAT model was confirmed, with a Nash-Sutcliffe efficiency (NSE) and determination coefficients (R2) of 0.76 and 0.99 respectively during calibration for monthly runoff, Nash-Sutcliffe efficiency (NSE) 0.63 and determination coefficients (R2) 0.99 respectively during validation for monthly runoff. The variation of precipitation in Muger sub basin decreased by (2010-2023), (2024-2037) and (2038-2050) from base period (1996-2009) will be 0.36%, 1.076% and 1.74% respectively, Maximum Temperature in sub basin increase from base period (1996-2009) by 0.55%, 2.32% and 4.6% and also minimum temperature in Muger sub basin increase by (2010-2023), (2024-2037) and (2038-2050) from base period (1996-2009) was 0.83%, 2.80 and 8.54% respectively. From this study, it was observed that due to climate change Average annual water yieldin Mugersub basinin (1996-2009), (2010-2023), (2024-2037), (2038-2050) is 4634.07 Mm3, 4525.92 Mm3, 4456.20 Mm3 and 4411.89 Mm3 respectively. Generally as Temperature increase in the study area the amount of rainfall decreases which directly affect the amount of water yield.

МОРФОМЕТРИЧЕСКИЕ ХАРАКТЕРИСТИКИ БАССЕЙНОВ РЕК СЕВЕРО-ЗАПАДНОГО СКЛОНА КРЫМСКИХ ГОР (НА ПРИМЕРЕ БАССЕЙНОВ РЕК ЗАПАДНЫЙ БУЛГАНАК, АЛЬМА, КАЧА, БЕЛЬБЕК, ЧЕРНАЯ)

Zapadnyy Bulganak, Alma, Kacha, Belbek, Chernaya rivers belong to the rivers of the north-western slope of the Crimean Mountains. The sources of the rivers are located on the north-western slopes of the Main Ridge of the Crimean Mountains, then the rivers flow from east to west almost parallel to each other. Up to about the middle of their course, they have a character typical of mountain streams (except for the Zapadnyy Bulganak River). The river valleys in the upper reaches are V-shaped, narrow, their slopes are dissected by numerous gullies and tributaries. There are almost no tributaries in the middle and lower reaches. In the low-water period (low-water period), drying is observed in the estuaries of rivers. The catchment basins have an elongated shape along the river, expanded in the upper part, which is the main feeding area.The considered river basins, although they have, in comparison with the rest, the river basins of the Crimean Peninsula, are better studied in general, but they are not sufficiently studied. In the article author deals with the main morphometric characteristics of river basins of the North-Western slope of the Crimean Mountains. Using Shuttle Radar Topography Mission (SRTM) and ArcGIS software for river basins Zapadnyy Bulganak, Alma, Kacha, Belbek, Chernaya are analyzed the following morphometric parameters – area of the basin, the symmetry of the basin, length of the basin, width of the basin, configuration and irregularity of the outline of river basin, the highest and lowest elevation within the basin, the average altitude of the river basin, the average slope of the river basin. Some of the morphometric indicators are calculated for the first time. For morphometric indicators that were partially previously calculated using topographic maps and published in literature, a comparison and analysis with the calculated data is provided. It is established that the using of SRTM and the ArcGIS software allows for fairly accurate measurements of morphometric indicators of the river basin.

Geological structure of the northern part of the Kara Shelf near the Severnaya Zemlya archipelago according to recent studies

Until recently, the North of the Kara Shelf was completely unexplored by seismic methods. Seismic and seismo-acoustic data that have appeared in recent years have made it possible to decipher features of the regional geological structure. This study solves the urgent problem of determining the prospects for the oil and gas potential of the North Kara sedimentary basin. The relevance of the research is associated with determining the prospects of the oil and gas potential of the North Kara sedimentary basin. The aim of the study is to clarify the age of the reflecting horizons using data on the geology of the island, as well as to determine the tectonic position of the sedimentary cover and basement structures in the north of the Kara shelf. The sedimentary cover is divided into three structural levels: Cambrian-Devonian, Middle Carboniferous-Cretaceous, Miocene-Quarter. The Cambrian-Devonian complex fills the deep troughs of the North Kara shelf. The most noticeable discontinuity is the base of Carboniferous-Permian rocks, lying on the eroded surface of folded Silurian-Devonian seismic complexes. The blanket-like plate part of the cover is composed of thin Carbon-Quarter complexes. The authors came to the conclusion that the fold structures of the Taimyr-Severozemelskiy fold belt gradually degenerate towards the Kara sedimentary basin and towards the continental slope of the Eurasian basin of the Arctic Ocean. A chain of narrow uplifts within the seabed relief, which correspond to narrow anticlines is traced to the West of the Severnaya Zemlya islands. Paleozoic rocks have subhorizontal bedding further to the West, within the Kara shelf. Mesozoic folding in the North of the Kara Sea is expressed exclusively in a weak activation of movements along faults. At the neotectonic stage, the shelf near Severnaya Zemlya was raised and the Mesozoic complexes were eroded. The modern seismic activity of the North Zemlya shelf is associated with the ongoing formation of the continental margin.

Subsidence and maturation evolution of a new lower-slope minibasin, Xingning Sag, northern South China Sea

Study of Subsidence and maturation evolution of a continental slope basin without a drilled well is an important problem in the early stage of deep-water exploration. Lack of some parameters, such as stratigraphic-age, porosity-depth relationship, exact paleo-water depth and heat flow value are common problems in the study of subsidence and maturity history. Using 46 long 2D seismic lines and paleo-water depth data from paleontological data of a well on the slope toe, the present study combines backstripping with thermal modeling to reconstruct the subsidence and maturation evolution of a lower-slope minibasin, Xingning Sag (XS), on the southeast Pearl River Mouth Basin (PRMB) of the South China Sea (SCS), now a new prospecting area. Stratigraphic-ages, porosity-depth relationship, lithology of XS were estimated using data from an adjacent basin. Paleo-water depths were obtained by clinoform geometry using seismic facies and paleontological method. With these parameters, the subsidence curves were created by backstripping. Crustal stretching factors (β) were obtained by best fit of tectonic subsidence curve and thermal modeling. With these stretching factors, the theoretical subsidence and heat flow values were obtained at the same time. Based on the heat flow value and the backstripping parameters, the maturation history of this basin was simulated. The result shows XS evolved through three cycles of subsidence during 46–23.03 Ma, 23.03–13.82 Ma and 13.82–0 Ma, respectively. Each cycle shows a rifting phase of relatively rapid tectonic subsidence followed a cooling phase of slow subsidence. Potential Eocene lacustrine source rocks are distributed primarily in the central depression area (Xingning main sub-sag), and would have entered the main oil-generation window and main gas generation during early- and mid-Miocene respectively.

A Shallow Seabed Dynamic Gas Hydrate System off SW Taiwan: Results From 3‐D Seismic, Thermal, and Fluid Migration Analyses

AbstractLarge amounts of methane, a potent greenhouse gas, are stored in hydrates beneath the seafloor. Sea level changes can trigger massive methane release into the ocean. It is not clear, however, whether surficial seafloor processes can cause comparable discharge. Previously, fluid migration was difficult to study due to a lack of spatially dense seismic and thermal observations. Here we examine a gas hydrate site at Four‐Way‐Closure Ridge off SW Taiwan using a high‐resolution 3‐D seismic cube, together with bottom‐simulating reflections (BSRs) mapped in the cube, a thermal probe data set, and 3‐D thermal modeling results. We document, on a scale of tens of meters, the interaction between surficial sedimentary processes, fluid flow, and a dynamic gas hydrate system. Fluid migrates upward through dipping permeable strata in the limb, the slope basin, and along thrust faults and ridge‐top normal faults. The seismic data also reveal several double BSRs that underlie seabed sedimentary sliding and depositional features. Abrupt changes in subsurface pressure and temperature due to the rapid seabed sedimentary processes can cause a rapid shift of the base of the gas hydrate stability zone. This shift may be either downward or upward and would result in the accumulation or dissociation of hydrate in sediments sandwiched by the double BSRs, respectively. We propose that dynamic surficial processes on the seafloor together with shallow focused fluid flow affect hydrate distribution and saturation at depth and may even result in methane expulsion into the ocean if such localized features are common along convergent plate boundaries.

Targeting groundwater potential zones using Electrical resistivity and GIS techniques in Kadavanar Sub-basin, South India

Geographical Information System techniques are widely used to determine suitable sites for groundwater recharge through artificial recharge techniques. The present research work is to identify suitable locations for constructing artificial recharge structures in the Kadavanar Sub-basin, South India. People in the Sub-basin mainly depend on the groundwater resources for drinking and irrigation purposes. Groundwater resources are often overexploited in many parts of this Sub-basin to meet the water demand leading to groundwater consumption. A lot of surfaces and sub-surface information and criteria are required for mapping the groundwater recharge zone. This is where the geographic information system [GIS] provides the right impetus besides the groundwater prospective zone to harness multilayered spatial data so that multi-criteria analysis is possible. This analysis integrates historic rainfall data analysis, groundwater level fluctuation, stream network, aquifer thickness, land use/land cover and basin slope. Drainage map, slope map and land use/land cover maps were prepared from satellite imageries. Vertical electrical sounding (VES) geophysical survey with Schlumberger electrode configuration was also conducted in the basin at 50 locations to map the aquifer thickness. Spatial variation maps for groundwater level and aquifer thickness were generated using GIS. Weighted aggregation method was used in this study to obtain groundwater recharge maps. Finally, multi-criteria analysis has been carried out to identify and assess the potential sites for groundwater recharge according to the associated weightages. It is established that GIS is best suited for the mapping of groundwater recharge zones. A similar study can be extended to any other hard-rock region facing water crises.

Thermal analysis of domestic type single Slope–Basin solar still under two different water depths

Thermal and economical performance evaluation was performed on a single slope single basin solar still at Bhopal (Latitude: 23°0.2599′′ N, Longitude: 77°0.4126′′ E), M.P., India. In this paper, evaporative and conductive heat transfer rates calculations is carried out on two different depths under 3 cm and 12 cm of the system. The Average evaporative (hew) and convective (hcw) heat transfer rates for 3 cm and 12 cm water depths are 2.265 W/m2oC and 0.814 W/m2oC respectively. Evaporative (hew) and convective (hcw) heat transfer coefficient calculations are done based on an experimental result and validated with Dunkle’s model. The results show that water depth of 12 cm higher daily yield output of 0.23885 Kg/hr for the active mode of operation. Economic evaluation, earned carbon credits, net CO2 emission and payback period calculations are also calculated and found that earned carbon credits is INR 20023.37 and net CO2 emission is 20.11591 tonnes during its lifespan of 20 years and payback period found to be 1.46 years. In embodied energy is also calculated and the total embodied energy is 5705.329 MJ.

Neoproterozoic non-glaciogenic iron formation: Insights from Fe isotope and elemental geochemistry of the Shalong iron formation from the Central Tianshan block, southern Altaids

The return of widespread banded iron formation (BIF) deposition during the Neoproterozoic Era after a more than one-billion-year hiatus appears to be a hallmark of the Neoproterozoic, and may be indicative of critical changes in the Earth’s environmental and tectonic conditions. However, consensus on the Fe sources and origin of Neoproterozoic iron formations (NIFs) remains elusive. Here we present new petrographic and geochemical data from the newly discovered Shalong NIF from the Central Tianshan block in order to constrain the iron source and elucidate the origin and depositional conditions of the NIF. The major and trace element composition of the Shalong NIF indicates that it is a relatively pure chemical sediment with a low detrital input. Rare earth elements and Y patterns (REY) exhibit seawater-like signature such as depletion in light REEs (LREEs) and enrichment in heavy REEs (HREEs). The weak positive Eu anomalies (Eu/Eu∗ = 1.11–1.31) and consistent chondritic Y/Ho ratios of 25 to 29 (average 26) suggest a predominant influx of low-temperature hydrothermal fluids. The geochemistry of the Shalong NIF also supports a predominant hydrothermal iron source characterized by low-temperature hydrothermal fluids. The lack of negative Ce anomalies, as well as weak positive Eu anomalies, and positive and variable δ56Fe values (−0.09‰ to +1.28‰) in the Shalong NIF indicates partial Fe2+ oxidation in a relatively large dissolved iron marine basin under oxygen-limited conditions. The Shalong NIF deposition likely took place on the slope of an extensional oceanic basin in a low energy environment. The Shalong NIF has a close association with metamorphized- bimodal volcanic rocks and predominant hydrothermal iron source. Combined with no sign for any glacial influence and depositional age prior to the global Sturtian glaciations, we suggest that the Shalong NIF is a non-glaciogenic Neoproterozoic iron formation in association with volcanic and hydrothermal activity. Our results, in conjunction with previous studies, suggest that glacial events are not essential or necessary for the origin of all the NIFs. Instead, hydrothermal activity seems to be a more important controlling factor for the build-up of ferruginous basins and subsequent iron oxidation events in the Neoproterozoic leading to the sudden recurrence of NIFs.

Crustal attenuation from USArray ML amplitude tomography

SUMMARYSeismic attenuation across the US is estimated using station ML magnitude data from the USArray. Station magnitudes are recalibrated back to amplitude and back projected in a 2-D tomography. Data represent the amplitudes of the horizontal components of the Lg phase. The western US shows regions of very high attenuation and contrasts with the lesser attenuation of the eastern US. Individual attenuation anomalies can be clearly tied to regional geology. Station gains show broad regional variations that match geographic regions. Most of the high-attenuation areas are regions of high geothermal activity suggesting that intrinsic attenuation dominates over scattering attenuation. An exception is the central San Andreas Fault zone because it lacks any localized heat-flow anomaly. The US east of the Rocky Mountains is bland and contains none of the high-attenuation regions of the western US. Instead, the central US has low-attenuation patches that do not obviously correspond to geologic province. Sediments of the Gulf Coast Plain, Willison Basin and Michigan Basin do show up as intermediate attenuation while the Illinois Basin, Appalachian Basin and other basins are not apparent. In Alaska, attenuation is generally less than the western US, but still much greater than the eastern US. In southeast Alaska, the Wrangell Volcanic Field causes a sizeable high-attenuation zone. The volcanic Aleutian Mountains also have high attenuation. However, moderate to high attenuation also correlates with the tertiary sedimentary basins in Alaska. The North Slope Basin does not seem to attenuate. Thicker crust and mountain roots tend to show less attenuation, if anything, but this correspondence is most likely due to differences in temperature and seismic velocity. Heat, scattering and young sedimentary basins create seismic attenuation in the continental crust.

Mesozoic Subduction Accretion History in Central Tibet Constrained From Provenance Analysis of the Mugagangri Subduction Complex in the Bangong‐Nujiang Suture Zone

AbstractThe Mugagangri Complex in central Tibet provides a record of the subduction accretion history between the Lhasa and Qiangtang terranes and consists of coherent sedimentary sequences, strongly dismembered formations, and siliciclastic‐matrix block‐in‐matrix mélange. We identified three different groups of sandstone within the Mugagangri Complex. Group 1 is volcaniclastic lithic (Q41F19L40, Lm16Lv77Ls7) and exhibits youngest U‐Pb detrital zircon (YDZ) ages of 177–170 Ma. Group 2 is litho‐quartzose (Q67F6L27, Lm23Lv63Ls13) with YDZ ages of 237–213 Ma. Groups 1 and 2 show provenance affinity with the Qiangtang terrane to the north. Group 3 is similar to Group 2 in detrital mode (Q67F2L31) and U‐Pb detrital zircon age spectra but is distinguished by more sedimentary fragments (Lm17Lv24Ls59), a 1,200–1,100 Ma age peak that is possibly characteristic of the Lhasa terrane to the south and YDZ ages of 284–246 Ma. During (and possibly prior to) Late Triassic time, the recycled orogen‐derived sandstones, including Group 2 and possibly Group 3, were deposited on the ocean floor adjacent to the Qiangtang terrane. During the early Middle Jurassic, the arc‐derived sandstone (Group 1) was deposited and accreted through the northward subduction of Bangong‐Nujiang oceanic lithosphere. During the late Middle to Late Jurassic, Groups 2 and 3 may have been deposited in a trench or trench slope basin, with Group 3 receiving detritus from both the Lhasa and Qiangtang terranes. These three groups of sandstone and ocean plate stratigraphy were mixed in the mélange during the accretion between the Lhasa and Qiangtang terranes.

MODELS TO PREDICT SLOPE LENGTH FROM OTHER WATERSHED ATTRIBUTES

Soil erosion by water is an extensive and increasing problem worldwide. Albeit, this problem has been recognized as a significant hazard in Iraq, yet the number of studies on this topic is very limited. Most of the models used for estimating soil erosion contain parameters for slope length factor (LS). A major constraint is the difficulty in extracting the LS factor. Accordingly, the current study was initiated with the main objective of deriving models to predict the slope length from relatively easy to measure basin characteristics with a reasonable accuracy. To achieve the above objective, standard methodologies were employed to describe 30 main basins with the upper part of Iraq in terms linear, areal and relief morphometric parameters. The majority of the delineated watersheds were characterized by having high slope lengths indicating lower drainage density and higher erosion rate. Linear and non-linear least squares techniques were applied to predict the slope length from other basin characteristics. Different indicators were used to test the performance of the proposed models and the approach was validated using K-fold procedure at independent basins. The results indicated that the 4-parameter regression model outperformed the remaining models of watershed slope length. The regressors of this model are bifurcation ratio, perimeter, and basin length and slope gradient.

Material damage caused by high-magnitude rainfall based on insurance data: Comparing two flooding events in the Lisbon Metropolitan Area and Madeira Island, Portugal

This research quantifies and compares the material damage caused by flooding resulting from the two most extreme rainfall events of the 21st century in two Portuguese regions, using insurance data: the Lisbon Metropolitan Area (LMA) and Madeira Island. During the 2000–2011 period, 24% of the claims and 40% of the payouts in the LMA were caused by the February 2008 event. In Madeira, the February 2010 event represented 50% of the claims and 88% of the payouts. The maximum rainfall values during the 2010 event more than doubling those recorded during the 2008 event. The steep slopes of the Madeira's drainage basins exacerbate the potential for flooding to cause damage. Peak discharges are higher and occur earlier than in the LMA's basins. Flash floods are the most important type of flooding in Madeira, unlike what occurs in the LMA, where urban flooding is most prevailent. The greater destructive capacity of flash floods, the higher magnitude of the triggering rainfall during the 2010 event and the higher flooding susceptibility of the Madeira's drainage basins justify the greatest material damage. The lower education levels and economic power of the Madeira's population may affect the capacity to purchase insurance and can explain the lower number of insurance policies, contributing for a higher vulnerability to flooding. The obtained results represent an important knowledge regarding flooding in Portugal for spatial planning, risk management and insurance companies.

A Hybrid Intelligence Model for the Prediction of the Peak Flow of Debris Floods

Debris floods, as one of the most significant natural hazards, often threaten the lives and property of many people worldwide. Predicting models are essential for flood warning systems to minimize casualties of debris floods. Since HEC-HMS (Hydrologic Engineering Center’s Hydrological Modelling System) cannot simulate debris flow, this study proposes a new hybrid model that uses artificial intelligence models to overcome HEC-HMS’s insufficiency in reflecting the sediment concentration effect on the debris floods. A sediment concentration is an effective factor for evaluating debris flood peak flows. This led to the proposal of new hybrid models for predicting the debris flood peak flows on the basis of hybridization of the artificial intelligence models (Bayesian Network (BN) and Support Vector Regression–Particle Swarm Optimization (SVR-PSO)) and HEC-HMS. To estimate the sediment concentration of floods by using the proposed artificial intelligence models, we nominated an average basin elevation, an average basin slope, a basin area, the current day rainfall, the antecedent rainfall of the past 3 days, and the streamflow of the previous day the previous day as the effective variables. In the validation stage, the average of the Mean Absolute Relative Error (MARE) of the estimated values were 0.024, 0.038, and 0.024 for the typical floods that occurred in the Navrood, Kasilian, and the Amameh basins in the north of Iran, respectively. Similarly, we obtained values of 0.038, 0.073, and 0.040 for the debris flood events for the three respective locations. After predicting the debris flood peak flows by the proposed hybrid HMS-BN and HMS-SVR-PSO models, the average of the MAREs for all debris flood events was reduced to 0.013 and 0.014, respectively. The comparison of MAREs of the examined hybrid models shows that the HMS-BN model results in higher accuracy than the HMS-SVR-PSO model in the prediction of the debris flood peak flows. Generally, the absolute error of prediction by the proposed hybrid model is reduced to one-third of the HEC-HMS. The prediction of the debris flood peak flows using the proposed hybrid model can be examined in the debris flood warning systems to reduce the potential damages and casualties in similar basins.