Flood Flow Velocity Research Articles

Study on the time-varying law of mechanics of the crossing suspended pipeline under flood action

In order to study the mechanical behavior of the river crossing pipeline before and after the flood, the suspended coefficient was defined, the correspondence between the suspended length of the pipeline and the flood flow velocity was characterized, and the flood hydrograph design encountered in the past 50 years was predicted according to the hydrological conditions of a pipeline crossing the river. Then, the dynamic change process of the X80 gas pipeline under the action of a flood is simulated by finite element software. Finally, the change law of pipeline mechanical behavior with time at each stage of river crossing pipeline under the condition that the suspended coefficient is known and a flood hydrograph is obtained. The results indicate that in the process of pipeline suspension from 5 m to pipeline failure, the failure time of pipelines with suspension coefficients of 0.005 and 0.01 is 3780s and 2200s, respectively. In the pipeline suspended 30–40 m stage, the impact of suspension length on pipeline stress exceeds the flood flow velocity, and the pipeline stress in this section increases greatly, and its stress growth rate is about 1.7 times the average growth rate of the pipeline suspension from 5 m to pipeline failure. Therefore, protective measures should be taken in emergency rescue before the X80 pipeline suspension of 30 m.

Research on the Vulnerability of the Community to Flood: A Case Study at the Downstream of Gianh River, Quang Binh Province

Flood is a frequent natural disaster which has a negative impact on the socio-economic activities of the community in the lower Gianh river area - one of the most vulnerability areas under the flood in the North Central Region, Vietnam. The aim of this paper is to assess the risk of flooding in the study area as well as point out the factors that increase the vulnerability of the local community. The study applies UNESCO-IHE vulnerability approach, combining the flood risk assessment method by MIKE FLOOD model and sociological investigation, with 90 household questionnaires (selected randomly and door-to-door interview). The main results include flood risk level maps (by analyzing inundation depth and flood flow velocities); data on community resilience to flood (resilience capacity and local people's perceptions on flood risks). These results are the basis for not only raising awareness about flood risks but also propose non-structural flood protection solutions for managers and local communities in the research areas.

Influence of check dams on flood hydrology across varying stages of their lifespan in a highly erodible Catchment, Loess Plateau of China

Check dams are applied worldwide as an effective approach for soil conservation. Its effect on hydrology, however, has not been fully understood. As a critical step towards revealing the lumped effect of check dams at the regional scale, this study explored the modified flood hydrology induced by check dams in a representative highly erodible catchment in the Loess Plateau, China. A coupled hydrological and hydraulic modeling approach was applied to simulate the flooding process in different stages of deposition and topographic changes in a check dam reservoir. The results suggest a paradigm shift of the dam effect on flood attributes, which transits from a total interception in the early stage of the dam to peak reduction and flood detention, rather than a complete loss of flood control functions, when it approaches the maximum capacity of sedimentation. Under the same level of deposition, the reduction of a minor flood by a check dam was higher than that of a major flood. The topographic changes contributed to the reduction of flood peak appreciably by reducing the flow velocity and retarding the flood propagation. Noticeably, this reduction was augmented with the advancement of siltation and topographic changes, indicating the persistence of the hydrologic effects of check dams in the long run. As a result of these hydrological changes, the reduction in the flood flow velocity induced by check dams suggests substantial reductions in sediment transport and channel erosion during floods. In addition, a dam system containing multiple, cascading check dams exhibits much more significant effect in modifying both hydrologic and hydraulic properties of flood than individual dams. The current research provides a mechanistic understanding of the effects of check dams on catchment hydrology under heavy rainstorm conditions in small catchments.

Flood risk mapping of the Sukamahi Dam failure with overtopping scenario

Sukamahi dam at Cisukabirus river, part of the upper Ciliwung watershed, located at Bogor regency. Sukamahi dam was designed for flood reduction purposes, especially for the downstream region, e.g., City of Bogor, Bogor regency, City of Depok, and Jakarta. Sukamahi dam will give flood reduction 13.53 m3/s with probability exceeded 2 %, and time to concentration (tc) for peak discharge (Qp) at least 4 hours longer than existing condition. Despite providing the benefits of flood control, the construction of dams also has the potential to increase the risk, i. E if a dam fails due to overtopping. Based on the Sukamahi dam flood failure scenario, dam failure has the potential to occur if the bottom outlet ( tunnel) and spillway fail when flood discharge with a 1000 year return period or more occur. Modeling of Sukamahi dam failure using 2 D HEC-RAS with unsteady flow analysis from sta 0 + 000 to STA 8 + 500 produces a map of inundation area of 36.89 Ha. The flood flow velocity is reaching 8.43 m/sec with a maximum flood flow depth of 69.72 m.

Effect of Partially Submerged Vegetation Distribution Directions on Flood Flow Resistance

Abstract The large-scale distribution of vegetation influences flood flow concentration. Natural and cultivated high plants impact the flood flow velocity field and volume distribution in a watersh...

Changes in Floodplain Vegetation Density and the Impact of Invasive Amorpha fruticosa on Flood Conveyance

Abstract Flood conveyance of floodplains is significantly influenced by the riparian vegetation cover, since vegetation affects flow velocity, therefore has a considerable impact on flood height and rate and pattern of sedimentation. However, climate change promotes the spread of invasive species, and their rapid growth results in dense vegetation stands, thus they have a significant impact on floodwater hydraulics. The aims of the present study are (1) to analyse the long-term changes in land-use and vegetation density on the Lower Tisza River, (2) to evaluate the role of the invasive Amorpha fruticosa in increasing vegetation density, and (3) to model the effect of dense floodplain vegetation on flood level and flood conveyance. Long-term (1784-2017) changes of land-use suggest that in natural conditions the study area was occupied by wetlands (92%), thus water covered the area for almost the whole year. In the 19th century, after levee constructions the wetlands were replaced by meadows and pastures (94%), then by the end of the 20th century planted and riparian forests replaced these land-covers. As a result, the mean roughness (0.14) of the floodplain has increased threefold until the early 21st century. Today forests are invaded by Amorpha fruticosa, which increases the vegetation density by 3% in riparian forests, by 23% in forest plantations, and by up to 100% in abandoned pastures and a rable lands. According to the results of HEC-RAS (Hydrologic Engineering Center’s River Analysis System) and CES (Conveyance Estimation System) models, if floodplain vegetation was managed and Amorpha fruticosa was cleared from the floodplain, peak flood level would decrease by 15 cm. Due to dense vegetation, the flood conveyance decreased by 4-6%, and the presence of Amorpha fruticosa reduced the flood flow velocities by 0.014-0.016 m/s. Accordingly, clearance of the floodplain from Amorpha fruticosa would have positive effects on flood protection, since peak flood stages would decrease and flood waves would shorten.

Neuroimaging and the preterm infant brain

In this issue of Journal of Pediatric Neuroradiology, Leijser et al. [1] explore the correlation between morphology of the intracranial vasculature and cerebral blood flow velocity, non-invasively respectively assessed using magnetic resonance angiography (MRA) and Doppler ultrasound in term-born infants and preterm infants at term equivalent age. Preterm birth is increasing and the rate of neurodevelopmental impairment, including motor and neurocognitive impairment, remains high in survivors [2]. Clinicians routinely need to provide parents and caregivers with prognostic information for these vulnerable newborns. Prediction of cognitive outcome early in life is of paramount importance to plan targeted cognitive intervention and neurorehabilitation. Non-invasive imaging techniques, in particular ultrasound, have been widely used in clinical practice to provide prognostic information. Magnetic resonance imaging (MRI) is less widely available and more expensive; however, the use of 3 Tesla field strength scanners and parallel imaging technique has significantly decreased exam duration and the need for sedation in the newborn population. Knowledge of the prognostic value of cranial ultrasound and MRI relies on a relatively small number of studies [3]. While normal ultrasound or MRI studies predict a low risk of future motor impairment in preterm infants, the prognostic implications of many abnormal findings, as well as of morphological and functional differences between term and preterm infants detected by ultrasound and MRI are not well understood. Therefore, there is a strong need to better comprehend the prognostic correlates of neuroimaging findings in preterm newborns. Previous neuroimaging studies have identified differences in cortical folding, gray matter volume, and white matter abnormalities between preterm and term born infants [4–7]. Dr. Leijser and her group focus their attention on the functional and morphological differences of the intracranial vasculature in these two groups of infants in the absence of overt brain pathology. After investigating the effects of preterm delivery on neonatal cerebral vasculature using MRA [8], the authors examine the correlation between vascular morphology assessed using MRA and functional metrics obtained using Doppler ultrasound [1]. This work is important for several reasons. First, a functional and morphological evaluation of the developing intracranial vasculature is only feasible using non-invasive imaging techniques, because post-mortem assessment of the brain cannot assess vascular geometry and functionality. Alterations in cerebral blood flow play a crucial role in the development of hypoxic-ischemic injury in preterm and term newborns and the cerebral flood flow velocity data provided in this paper may serve as a reference for many potential applications in research and clinical practice. Understanding patterns of cerebrovascular morphology and cerebral blood flow velocity in preterm neonates and their correlation with neurological outcome could be proven useful in the future to identify infants at risk of developmental and cognitive deficit. *Address for correspondence: Maria Vittoria Spampinato, Department of Radiology and Radiological Sciences, Medical University of South Carolina, 96 Jonathan Lucas Street, MSC 323, Charleston, SC, USA. Tel.: +1 843 792 0209; Fax: +1 843 792 1705; E-mail: spampin@ musc.edu. Journal of Pediatric Neuroradiology 2 (2012) 69–70 DOI 10.3233/PNR-2012-012 IOS Press 69

A hydro-sedimentary modeling system for flash flood propagation and hazard estimation under different agricultural practices

Abstract. A modeling system for the estimation of flash flood flow velocity and sediment transport is developed in this study. The system comprises three components: (a) a modeling framework based on the hydrological model HSPF, (b) the hydrodynamic module of the hydraulic model MIKE 11 (quasi-2-D), and (c) the advection–dispersion module of MIKE 11 as a sediment transport model. An important parameter in hydraulic modeling is the Manning's coefficient, an indicator of the channel resistance which is directly dependent on riparian vegetation changes. Riparian vegetation's effect on flood propagation parameters such as water depth (inundation), discharge, flow velocity, and sediment transport load is investigated in this study. Based on the obtained results, when the weed-cutting percentage is increased, the flood wave depth decreases while flow discharge, velocity and sediment transport load increase. The proposed modeling system is used to evaluate and illustrate the flood hazard for different riparian vegetation cutting scenarios. For the estimation of flood hazard, a combination of the flood propagation characteristics of water depth, flow velocity and sediment load was used. Next, a well-balanced selection of the most appropriate agricultural cutting practices of riparian vegetation was performed. Ultimately, the model results obtained for different agricultural cutting practice scenarios can be employed to create flood protection measures for flood-prone areas. The proposed methodology was applied to the downstream part of a small Mediterranean river basin in Crete, Greece.

Flood Flow Velocity of the Mikasa River Estimated by Stereoscope at the Time of the 2003 Kyushu Heavy Rainfalls

Flood Flow Velocity of the Mikasa River Estimated by Stereoscope at the Time of the 2003 Kyushu Heavy Rainfalls

3 DIMENSIONAL FLOW ANALYSES AROUND RIVER STRUCTURES BASED ON FLOOD-FLOW MEASUREMENT BY MEANS OF ADCP

In the present study, an ADCP flood measurement and 3D flow analyses were conducted around the Gudo point near the Shimanto-river bridge which is located at 9.5km upstream from the mouth of Shimanto River in Shikoku-island Japan, to reveal the details of flow structure around the bridge. There are some river structures such as bridge piers and bed protections around the bridge. There is also a large local scouring in the right bank side of the bridge. The scouring has progressed for a long period to 10m depth below water surface. In order to estimate the accurate discharge, detail flow structures considering with the complicated surroundings are needed for river management such as flood control. As a result, flood-flow velocity and bed profile were successfully measured by the ADCP and 3D flow was analyzed far downstream area from the bridge.

SURVEY OF VERTICAL FORMATION OF FLOW VELOCITY WITH RIPARIAN WOODS ON 2005-FLOOD IN BIBAI RIVER

Riparian wood area is assumed to be dead water section on study for flowing ability. But, calculation results of water level might not correspond with observations on medium-small scale rivers. We surveyed about vertical formation of flood flow velocity on the cross section including riparian wood area in Bibai River on August 22, 2005. As a result, about 27% of total flow quantity flowed down through the riparian woods on this survey section. And, formation of flow velocity on woods area almost agrees with the theoretical value. But, formation of flow velocity outside the woods is lower than the theoretical one.

Effects of isoflurane on the cerebral flood flow velocity and the systemic blood flow velocity: dose dependency

European Society of Anaesthesiologists; 8th Annual Meeting with the Austrian International Congress; Vienna, Austria, 1-4 April 2000