scholarly journals Influence of different sources of topographic data on flood mapping: urban area São Vendelino municipality, southern Brazil

RBRH ◽  
2020 ◽  
Vol 25 ◽  
Author(s):  
Fernando Campo Zambrano ◽  
Masato Kobiyama ◽  
Marco Alésio Figueiredo Pereira ◽  
Gean Paulo Michel ◽  
Fernando Mainardi Fan
Keyword(s):  
Cross Sections ◽  
Field Survey ◽  
Flood Mapping ◽  
Mean Velocity ◽  
Topographic Data ◽  
Digital Elevation ◽  
Wetted Area ◽  
Elevation Model ◽  
Best Fit ◽  
Different Sources

ABSTRACT Generally, the base for any flood mapping is the topography information whose resolution determines the map accuracy. Furthermore, river bathymetry in detail and the type of used model are also relevant. Therefore, the objective of the present study was to evaluate the influence of different sources of topographic data on the flood mapping by using the CAESAR-Lisflood model and three Digital Elevation Model (DEM) configurations, among which two were freely available, and the other was generated with field survey (topography and bathymetry). First, the resolution and precision of each DEM were evaluated, from the comparison of different cross-sections, besides the variation of the wetted area and absolute value of the relative error in mean velocity as a function of depth. Subsequently, after elaborating flood maps with each DEM, the results were compared in terms of flood area, mean flood width and flow depth. It is observed that the more accurate resolution, the smaller the flood area becomes. The flood map elaborated with the DEM through field survey had the best fit to the observed area. However the relation between the topographic resolutions and flow-depths was not clear in obtained results.

scholarly journals Reconstructing Pre-Industrial Long Distance Roads in a Hilly Region in Germany, Based on Historical and Archaeological Data

2017 ◽  
Vol 1 (2) ◽  
pp. 642-660 ◽  
Author(s):  
Irmela Herzog
Keyword(s):  
Cross Sections ◽  
Lidar Data ◽  
Long Distance ◽  
Early 19Th Century ◽  
Digital Elevation ◽  
Hilly Region ◽  
Local Accuracy ◽  
Cost Paths ◽  
Elevation Model ◽  
The One

The aim of this contribution is on the one hand to map pre-industrial long distance roads located in a hilly region east of Cologne, Germany, as exactly as possible and on the other hand to assess the accuracy of least-cost approaches that are increasingly applied by archaeologists for prehistoric road reconstruction. Probably the earliest map covering the study area east of Cologne dates back to 1575. The map is distorted so that rectification is difficult. But it is possible to assess the local accuracy of the map and to transfer the approximate routes to a modern map manually. Most of the area covered by the 1575 map is also depicted on a set of more accurate maps created in the early 19th century and a somewhat later historical map set (ca. 1842 AD). The historical roads on these rectified historical maps close to the approximate roads were digitized and compared to the outcomes of least-cost analysis, specifically least-cost paths and accessibility maps. Based on these route reconstructions with limited accuracy, Lidar data is checked to identify remains of these roads. Several approaches for visualizing Lidar data are tested to identify appropriate methods for detecting sunken roads. Possible sunken roads detected on the Lidar images were validated by checking cross sections in the digital elevation model and in the field.

scholarly journals Automated Conflation of Digital Elevation Model with Reference Hydrographic Lines

2020 ◽  
Vol 9 (5) ◽  
pp. 334
Author(s):  
Timofey E. Samsonov
Keyword(s):  
Spatial Analysis ◽  
Digital Elevation Model ◽  
Spatial Data ◽  
Drainage Network ◽  
Map Generalization ◽  
Data Types ◽  
Digital Elevation ◽  
Elevation Data ◽  
Elevation Model ◽  
Different Sources

Combining misaligned spatial data from different sources complicates spatial analysis and creation of maps. Conflation is a process that solves the misalignment problem through spatial adjustment or attribute transfer between similar features in two datasets. Even though a combination of digital elevation model (DEM) and vector hydrographic lines is a common practice in spatial analysis and mapping, no method for automated conflation between these spatial data types has been developed so far. The problem of DEM and hydrography misalignment arises not only in map compilation, but also during the production of generalized datasets. There is a lack of automated solutions which can ensure that the drainage network represented in the surface of generalized DEM is spatially adjusted with independently generalized vector hydrography. We propose a new method that performs the conflation of DEM with linear hydrographic data and is embeddable into DEM generalization process. Given a set of reference hydrographic lines, our method automatically recognizes the most similar paths on DEM surface called counterpart streams. The elevation data extracted from DEM is then rubbersheeted locally using the links between counterpart streams and reference lines, and the conflated DEM is reconstructed from the rubbersheeted elevation data. The algorithm developed for extraction of counterpart streams ensures that the resulting set of lines comprises the network similar to the network of ordered reference lines. We also show how our approach can be seamlessly integrated into a TIN-based structural DEM generalization process with spatial adjustment to pre-generalized hydrographic lines as additional requirement. The combination of the GEBCO_2019 DEM and the Natural Earth 10M vector dataset is used to illustrate the effectiveness of DEM conflation both in map compilation and map generalization workflows. Resulting maps are geographically correct and are aesthetically more pleasing in comparison to a straightforward combination of misaligned DEM and hydrographic lines without conflation.

scholarly journals Managing the Flood Waves from Hemrin Dam

2021 ◽  
Vol 27 (7) ◽  
pp. 42-52
Author(s):  
Hajir Majid Ghali ◽  
Riyadh Z. Azzubaidi
Keyword(s):  
Cross Sections ◽  
Design Flood ◽  
Digital Elevation ◽  
Full Capacity ◽  
High Flood ◽  
Diyala River ◽  
Elevation Model ◽  
Strategic Study ◽  
Drop Structure ◽  
Flood Waves

Diyala Governorate was exposed recently to high flood waves discharged from Hemrin Dam to Diyala River when the dam reached its full capacity. The recently recorded discharge capacity of Diyala River was reduced to just 750m3/s. This exposes cities and villages along the Diyala River to flood risk when discharging the flood waves, which may reach 3000 m3/s. It is important to manage, suggest, and design flood escapes to discharge the flood waves from Hemrin Dam away from Diyala River. This escape branches from Hemrin Lake towards Ashweicha Marsh. One dimensional hydraulic model was developed to simulate the flow within the escape by using HEC-RAS software. Eighty-two cross-sections were extracted from the digital elevation model for the escape and used as geometric data. Moreover, thirty cross-sections for the Diyala River were utilized from the Strategic Study for Water and Land Resources in Iraq. Since the escape passes through two regions of different geological formations, two roughness coefficients of 0.035and0.028were used. Two discharge cases were applied3000m3/s, which is the 500 years return period extreme hydrograph of Hemrin Dam, and 4000 m3/s, which is the design discharge of Hemrin Dam spillway. A spillway was proposed at the escape entrance with crest level 105m.a.m.s.l., followed by a drop structure with eighteen rectangular steps

scholarly journals Technical Note: Water flow routing on irregular meshes

2006 ◽  
Vol 3 (6) ◽  
pp. 3675-3689 ◽  
Author(s):  
D. Bänninger
Keyword(s):  
Water Flow ◽  
Cross Section ◽  
Cross Sections ◽  
Technical Note ◽  
Hill Slope ◽  
Digital Elevation ◽  
Irregular Meshes ◽  
Elevation Model ◽  
Local Gradient ◽  
Flow Cross

Abstract. For spatial explicit hydrological modelling an algorithm was needed which works as cellular automata on irregular meshes. From literature it was found that usual algorithms applied for this purpose do not route the water flow correctly to its adjacent cells. In this study the hydraulic linking between mesh cells is done by calculating the flow cross section between the mesh cells. The flow cross sections are positioned in the centre of the mesh edges and are perpendicular to the local gradient of the digital elevation model. The presented algorithm is simple in its implementation and efficient in computation. It is shown that the proposed algorithm works correctly for different synthesised hill slope shapes.

scholarly journals Technical Note: Water flow routing on irregular meshes

2007 ◽  
Vol 11 (4) ◽  
pp. 1243-1247 ◽  
Author(s):  
D. Bänninger
Keyword(s):  
Water Flow ◽  
Cross Sections ◽  
Technical Note ◽  
Spatially Explicit ◽  
Hill Slope ◽  
Digital Elevation ◽  
Irregular Meshes ◽  
Elevation Model ◽  
Local Gradient ◽  
Flow Cross

Abstract. For spatially explicit hydrological modelling an algorithm was required that works as a cellular automata on irregular meshes. From literature it was found that the usual algorithms applied for this purpose do not route the water flow correctly between adjacent cells. In this study the hydraulic linking between mesh cells is done by calculating the flow cross section between the mesh cells. The flow cross sections are positioned in the centre of the mesh edges and are perpendicular to the local gradient of the digital elevation model. The presented algorithm is simple in its implementation and efficient in computation. It is shown that the proposed algorithm works correctly for different synthesised hill slope shapes.

scholarly journals Flood mapping in small ungauged basins: a comparison of different approaches for two case studies in Slovakia

2018 ◽  
Vol 50 (1) ◽  
pp. 379-392 ◽  
Author(s):  
Andrea Petroselli ◽  
Matej Vojtek ◽  
Jana Vojteková
Keyword(s):  
Hydrologic Modeling ◽  
Hydraulic Modeling ◽  
Flood Mapping ◽  
Ungauged Basins ◽  
Dem Resolution ◽  
Digital Elevation ◽  
Design Hydrographs ◽  
Elevation Model ◽  
Event Based ◽  
Relief Area

Abstract Flood mapping is a crucial element of flood risk management. In small and ungauged basins, empirical and regionalization approaches are often adopted to estimate the design hydrographs that represent input data in hydraulic models. In this study, two basins were selected in Slovakia and different methodologies for flood mapping were tested highlighting the role of digital elevation model (DEM) resolution, hydrologic modeling and the hydraulic model. Two DEM resolutions (2 m and 20 m) were adopted. Two hydrologic approaches were employed: a regional formula for peak flow estimation and the EBA4SUB model. Two hydraulic approaches (HEC-RAS and FLO-2D) were selected. Different combinations of hydrologic and hydraulic modeling were tested, under different spatial resolutions. Regarding the DEM resolution, results showed its fundamental importance in the low relief area while its effect was secondary in the moderate relief area. Regarding the hydrologic modeling, results confirmed that it affects the results of the flood areas in the same way independently of DEM resolution and that when using event-based models, the hydrograph shape determination is fundamental. Regarding the hydraulic modeling, this was the step where major differences in the flood area estimation were found.

scholarly journals Surface topography and ice flow in the vicinity of the EDML deep-drilling site, Antarctica

2007 ◽  
Vol 53 (182) ◽  
pp. 442-448 ◽  
Author(s):  
Christine Wesche ◽  
Olaf Eisen ◽  
Hans Oerter ◽  
Daniel Schulte ◽  
Daniel Steinhage
Keyword(s):  
Surface Topography ◽  
Ice Core ◽  
Surface Strain ◽  
Mean Velocity ◽  
Velocity Magnitude ◽  
Digital Elevation ◽  
Dronning Maud Land ◽  
Drilling Site ◽  
Flow Compression ◽  
Elevation Model

AbstractInterpretation of ice-core records requires accurate knowledge of the past and present surface topography and stress–strain fields. The European Project for Ice Coring in Antarctica (EPICA) drilling site (75.0025° S, 0.0684° E; 2891.7 m) in Dronning Maud Land, Antarctica, is located in the immediate vicinity of a transient and forking ice divide. A digital elevation model is determined from the combination of kinematic GPS measurements with the GLAS12 datasets from the ICESat. Based on a network of stakes, surveyed with static GPS, the velocity field around the drilling site is calculated. The annual mean velocity magnitude of 12 survey points amounts to 0.74 m a–1. Flow directions mainly vary according to their distance from the ice divide. Surface strain rates are determined from a pentagonshaped stake network with one center point close to the drilling site. The strain field is characterized by along-flow compression, lateral dilatation and vertical layer thinning.

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