Ad-hoc estimation of landslide-generated impulse waves – from the lab to the field

<p>Landslide tsunamis generated by extremely rapid subaerial mass wasting are also referred to as impulse waves and may occur both along coastal areas and in inland waters including engineered reservoirs. The hydraulic process chain comprising wave generation, propagation, and run-up needs to be comprehensively assessed to predict whether these waves represent a threat to the shore and adjacent infrastructure. Hazard assessment studies based on site-specific hydraulic laboratory models and numerical simulations may generally yield quite accurate predictions of the expected wave and run-up heights. While the former involves the availability of specialized lab infrastructure and instrumentation, the latter requires in-depth knowledge of suitable numerical methods as well as experience in their application to scenarios at prototype-scale. Therefore, both approaches are time-consuming, involve high costs, and pose substantial entry thresholds for practitioners. Especially in emergency situations, when first-order estimations need to be quickly at hand, the ad-hoc applicability of these approaches may therefore be limited.</p><p>Motivated by an imminent landslide hazard at Carmena reservoir, Switzerland, in 2002, the national supervisory authority for dam safety, the Swiss Federal Office of Energy, commissioned the development of a fast and readily applicable computational procedure. As a result, the first edition of the so-called ‘impulse wave manual’ was published in 2009 and provides an extensive literature review of generally applicable equations derived from lab experiments. It combines selected equations into a coherent computational framework covering all stages of an impulse wave event’s hydraulic process chain. Based on the estimation of e.g. wave and run-up heights, this manual allows to rapidly implement mitigation measures including reservoir drawdown or precautionary evacuation. In addition to an improved emergency planning, the manual proved to be an inexpensive tool to obtain an estimation of an impulse wave event’s magnitude during the preliminary design phase of new reservoirs. Back in 2009, the manual’s literature analysis already identified specific research gaps, leading to the initiation of further experimental investigations. Following these research efforts over the past ten years, a second edition of the manual was published in 2019 featuring an updated computational procedure.</p><p>This contribution provides a brief introduction to the updated computational procedure and applies it to prototype events with available survey data, e.g. Chehalis Lake, Canada, in 2007. The comparison to prototype data allows to highlight the procedure’s capabilities as well as its limitations for future ad-hoc estimations of landslide-generated impulse waves.</p>

Determination of compound channel apparent shear stress: application of novel data mining models

Momentum exchange in the mixing region between the floodplain and the main channel is an essential hydraulic process, particularly for the estimation of discharge. The current study investigated various data mining models to estimate apparent shear stress in a symmetric compound channel with smooth and rough floodplains. The applied predictive models include random forest (RF), random tree (RT), reduced error pruning tree (REPT), M5P, and the distinguished hybrid bagging-M5P model. The models are constructed based on several correlated physical channel characteristic variables to predict the apparent shear stress. A sensitivity analysis is applied to select the best function tuning parameters for each model. Results showed that input with six variables exhibited the best prediction results for RF model while input with four variables produced the best performance for other models. Based on the optimised input variables for each model, the efficiency of five predictive models discussed here was evaluated. It was found that the M5P and hybrid bagging-M5P models with the coefficient of determination (R2) equal to 0.905 and 0.92, respectively, in the testing stage are superior in estimating apparent shear stress in compound channels than other RF, RT and REPT models.

SEDIMENTATION MANAGEMENT AT RAYAP IRRIGATION CHANNEL TERSIER II IN PATRANG SUB-DISTRICT OF JEMBER REGENCY

Rayap irrigation channel Tersier II is one of irrigation channel which has been supplying hydraulic flow to 31 hectares of ricefield area, and it is located at the Rayap irrigation sector – Renteng village, Patrang sub-district. In the last two years, this channel suffered from the landslide over the ridge on the left and the right bank. At the same time, those landslide materials covered the entire channel and causing a sediment accumulation, which always influences harmly toward the hydraulic process in the site of irrigation. As the point of consideration, this irrigation problem must be conducted a deep and holistic analysis in predicting the amount of sediment in the form of prevention mechanism for the sake of the operational irrigation sector. The research result methodology using a depth-integrated & point sample to identify the characterization and grain size of the sediment as much as 500 grams. The known water surface elevation is used to be a variable of steady flow analysis using HEC-RAS v.5.0.3, and the simulation flow is 0.0276 m2/detik with the accumulation sediment per year 1.0242 tons. These serial events are followed by the gradation in the very low basement of a channel as much as 30-80 centimeters aboveground. The specific recommendation channel profile to recover and provide the sufficient capacity of incoming sedimentation with the profile design in the form of natural trapezoid with the bottom width 1.8 meters and height minimum of channel 0.6 meters equipped by the channel normalization once a year. Saluran irigasi Rayap Tersier II merupakan salah satu saluran irigasi yang mengaliri petak persawahan seluas 31 Ha dan berada pada Daerah Irigasi Rayap Desa Renteng Kecamatan Patrang. Selama 2 tahun terakhir saluran ini mengalami longsor pada tebing dan lereng-lereng yang berada pada bagian atas saluran. Di saat yang bersamaan pula saluran tertutup kemudian terjadi akumulasi sedimen yang dapat mengganggu kinerja distribusi air pada baku sawah menjadi kurang maksimal. Melihat pentingnya peranan saluran perlu dilakukan langkah penanganan berupa pengendalian sedimen yang berpotensi muncul tiap tahunnya, maka dilakukan penelitian perilaku sedimen dengan metode depth integrated & point sample untuk mengetahui jumlah akumulasi sedimen yang terbawa arus tiap tahunnya dengan pengambilan total sampel di 5 titik seberat 500 gram. Bedasarkan data hasil pengukuran berupa tinggi muka air, cross section dan long section saluran maka, dilakukan analisis aliran seragam menggunakan HEC-RAS v.5.0.3. Hasil analisis hidrolik berupa kecepatan saluran sebesar 0.0276 m2 /detik dengan tingkat akumulasi sedimen per tahunnya sebanyak 1.0242 ton per tahun. Proses sedimentasi menyebabkan kenaikan dasar saluran (agradasi) setinggi 30-80 centimeter dari permukaan dasar tanah awal. Rekomendasi saluran untuk penanggulangan sedimentasi pada saluran perlu dilakukan normalisasi saluran irigasi berupa desain ulang berbentuk trapesium dengan tinggi jagaan setinggi 0.6 meter, lebar minimum saluran 1.8 meter, kemiringan saluran 0.006-0.336%, nilai koefisien kekasaran (n=0.03) dengan jadwal pengerukan rutin sebanyak 1 tahun sekali.

Weathering-induced deformation of crushed weak rocks and its countermeasure

Geotechnical issues such as differential settlements have been reported usually in embankments made of materials derived from weak rocks such as mudstones, siltstones, and shales. The primary cause of the issue is a gradual weakening due to weathering. Crushed weak rocks tend to turn into smaller particles under repeated wetting and drying processes. This phenomenon is a mechanical-hydraulic process known as “slaking”. The present paper discusses the deformation of crushed weak rocks due to slaking and its countermeasure. We performed a series of one-dimensional slaking tests on several weak rocks. We first performed one-dimensional compression tests on dried samples, and applied wetting and drying cycles to the samples while keeping the compression stress constant. The test results revealed that particle size distribution of the samples was broadened due to cyclic wetting and drying processes and that significant compression was exhibited. Moreover, we explored possible countermeasures for reducing the slaking-induced deformation and revealed that compacting the soil to a denser state is the most effective way in reducing the slaking-induced deformation of the crushed mudstone.

Wordsworth's Dropsy: Flux and Figure in The Excursion

This essay traces how William Wordsworth engages with both Romantic medical discourse and aesthetic theory by insisting that the mind is physically embodied, and finds his most complex and compelling treatment of this subject in his long poem of 1814, The Excursion. Adapting the formal model of poesis as a hydraulic process that he had theorized in the ‘Preface’ to Lyrical Ballads, the Wordsworth of 1814 considers minds as embodied brains governed by the influx of both liquid and language: the discovery of a waterlogged Voltaire corresponds to the shape of the Solitary's psychology through the formal mechanisms of intake, excess, and outflow. In this poem, however, Wordsworth's well-established hydraulics take on a newly pathological function, as his characters employ the imagery of the dropsy of the brain, or hydrocephalus, as they investigate and attempt to treat the Solitary's morbid state of being. What emerges throughout The Excursion – and, in turn, in ‘Simon Lee’ – is that the physical register of disease stands in for the characters' emotional states as a sylleptic structure of feeling. Ultimately, Wordsworth's dropsical brains bring into focus the Romantic idea of poetry as organic form, to ask how mechanistic and organic models might be reconciled in his notion of the hydraulic mind.