Determination Of Flow Direction Research Articles

Flow tweezing of anisotropic magnetic microrobots in a dynamic magnetic trap for active retention and localized flow sensing.

Controlled manipulation of microscale robotic devices in complex fluidic networks is critical for various applications in biomedical endovascular sensing, lab-on-chip biochemical assays, and environmental monitoring. However, achieving controlled transport and active retention of microscale robots with flow sensing capability has proven to be challenging. Here, we report the dynamic tweezing of an anisotropic magnetic microrobot in a rotating magnetic trap for active retention and localized flow sensing under confined fluidic conditions. We reveal a series of unconventional motion modes and the dynamics of the microrobot transporting in a confined fluidic flow, which manifest themselves as transitions from on-trap centre rolling to large-area revolution and off-trap centre rolling with varying rotating frequencies. By retaining the robot within the magnetic trap and its motion modulated by the field frequency, the off-centre rolling of the microrobot endows it with crucial localized flow sensing capabilities, including flow rate and flow direction determination. The magnetic microrobot serves as a mobile platform for measuring the flow profile along a curved channel, mimicking a blood vessel. Our findings unlock a new strategy to determine the local magnetic tweezing force profile and flow conditions in arbitrary flow channels, revealing strong potential for microfluidics, chemical reactors, and in vivo endovascular flow measurement.

Time-of-flight anemometry using a displacement plate-beamsplitter

We propose the use of a second surface mirror as a displacement plate-beamsplitter to provide significant simplification and cost reduction of time-of-flight anemometry (ToFA), without sacrificing precision and accuracy. These benefits are most pronounced for long-range applications. Our method’s principle benefits are due to the few and simple components it requires as well as low sensitivity to both temperature effects and light source incoherence. We found that precise and accurate results are possible using a common consumer mirror as the main optical element and an inexpensive diode laser as the light source, which could broaden access to laser anemometry and make many industry applications economically feasible. The nature of the design also permits an increase in range for a given laser power since the method can utilize the entire optical area of the focusing lens/mirror independent of other design considerations and the cost of a flat second-surface mirror is usually negligible. To characterize the performance of this method, we develop a Cramer–Rao bound (CRB) for a general class of ToFA’s with multiple Gaussian beams under signal-independent Gaussian white noise. For a given measurement volume, the lowest velocity uncertainty is achieved by creating a standard two-sheet geometry: power-matching the first two beams by adjusting the beamsplitter and blocking the rest of the beams is optimal. However, keeping the higher order beams permits determination of flow direction. Conditions to achieve beam power-matching are given. An anemometer is built using a diode laser with 12 mw 405 nm beam using a total of just three transmitting optical components. Our setup has an accuracy of 99.1%. The worst-case precision of 96.7% nearly achieves the CRB, although optimizing the setup more can lower the bound, and therefore allow increase in the performance by an order of magnitude or more.

Determining Flow Propagation Direction from In-Flight Array Surface Pressure Fluctuation Data

When characterizing spatial coherence properties of turbulent boundary-layer surface pressure fluctuation data, it is important to determine the local flow direction first. Without flow direction, it is very easy to introduce errors due to misalignment between sensors and the flow. For cases with two-dimensional microphone distributions, a method of determining flow direction from the orientation of the coherent pressure in spatial domain was introduced recently. If the data are analyzed in wavenumber domain, flow information can be obtained by the position and orientation of the convective ridge. In this publication, flow directions determined from a revised spatial domain approach and from two wavenumber domain approaches are considered. It was found that the result from the spatial domain approach and the result from the orientation of the convective ridge are similar for most frequencies, while the result based on the position of the convective ridge differs in the lower frequency range. Tilted convection of coherent structures in the turbulent boundary layer is discussed as a possible cause of these observations. A modification of the analytical model for surface pressure coherence is derived that takes the findings into account.

Economic optimization of heat exchanger networks based on geometric parameters using hybrid genetic-particle swarm algorithm technique

PurposeThe purpose of this study is to provide a method for designing the shell and tube heat exchangers and examine the total annual cost of heat exchanger networks from the economic view based on the careful design of equipment.Design/methodology/approachAccurate evaluation of heat exchanger networks performance depends on detailed models of heat exchangers design. The simulations variables include nine design variables such as flow direction determination of each of the two fluids, number of tubes, number of tube passes, length of tubes, the arrangement of tubes, size and percentage of baffle cut, tube diameter and tube pitch. The optimal designing of the heat exchangers is based on geometrical and hydraulic modeling and using a hybrid genetic particle swarm optimization algorithm (PSO-GA) technique. In this paper, optimization and minimization of the total annual cost of heat exchanger networks are considered as the objective function.FindingsIn this study, a fast and reliable method is used to simulate, optimize design parameters and evaluate heat transfer enhancement. PSO-GA algorithms have been used to minimize the total annual cost, which includes investment costs of heat exchangers and pumps, operating costs (pumping) and energy costs for utilities. Three case studies of four, six and nine streams are selected to demonstrate the accuracy of the method. Reductions of 0.55%, 23.5% and 14.78% are obtained in total annual cost for the selected streams, respectively.Originality/valueIn the present study, a reliable method is used to simulate and optimize design parameters and the economic optimization of the heat exchanger networks. Taking into account the importance of shell and tube heat exchangers in industrial applications and the complexity in their geometry, the PSO-GA methodology is adopted to obtain an optimal geometric configuration. The total annual cost is chosen as the objective function. Applying this technique to case studies demonstrates its ability to accurately design heat exchangers to optimize the objective function of the heat exchanger networks by giving the detail of design.

Real-time evaluation of swallowing in patients with oral cancers by using cine-magnetic resonance imaging based on T2-weighted sequences

The aim of this study was to evaluate whether a new cine-magnetic resonance imaging (CMRI) technique might be useful for evaluating swallowing function in patients with different types of oral cancers by assessing 12 CMRI-related parameters. In total, 111 patients with oral cancers were evaluated. We examined whether visualization of fluid flow and determination of flow direction to the trachea or the esophagus were possible with CMRI. We evaluated the correlations between CMRI-related parameters and self-reported dysphagia scores as the status of dysphagia, T classification groups as tumor staging for preoperative patients, alterations in CMRI-related parameters between pre- and postoperative patients, and the degree of invasiveness of oral cancer surgery. We could judge the flow direction to the esophagus on CMRI in all 111 patients. Six CMRI-related parameters showed significant correlations with dysphagia status. Increases in CMRI-related parameters were significantly related to deterioration of swallowing status, as shown by a decrease in self-reported dysphagia scores, advances in the T classification, and degree of invasiveness of oral cancer surgery. The results of the present study suggest that CMRI can be used to directly visualize swallowing dynamics and objectively evaluate the swallowing complaints of patients with oral cancer.

Mapping of Pyroclastic Density Currents Hazards and Assessment of Related Risks by AMS Technique in the West-Cameroon Highlands: Case of Bambouto and Bamenda Volcanoes

Ignimbritic flow deposits which derived from pyroclastic density currents (PDCs) are mostly observed in West-Cameroon Highlands located in the central portion of the Cameroon Volcanic Line (CVL), especially in Bambouto (21.12 - 0.50 Ma) and Bamenda (27.40 - 0 Ma) volcanoes. These deposits covering approximately 27% (≈195 km2) of the volcanoes surface with thickness ranging from 30 to 200 m representing a total volume estimated at 20 km3. Because of the intense weathering of the ignimbritic formations after their setting up and being buried by basaltic and trachtytic flows, the initial volume of these pyroclastic deposits is really much larger. Soil fertility has fostered an important population growth (more than 1,200,000 people) in these volcanoes. The economic and agropastoral activities on the flanks and inside the caldera of the volcanoes are estimated at about $US7.5 billion. In this paper, we evaluate and realize cartography of the hazards associated to ignimbritic eruptions which are most disastrous in term of volcanic process in this region. Magnetic studies, specifically, Anisotropy of Magnetic Susceptibility (AMS) method has been utilized for the determination of flow directions in visually nearly isotropic ignimbritic deposits outcrops. The AMS data reported from the Bamenda and Bambouto volcanoes ignimbrites produced significant informations about the depositional scheme of the PDCs. In most sites, magnetic lineations and principally magnetic foliation are reliably parallel to downhill directions, frequently with an upslope imbrication. Inferred palaeoflow directions based on the field indicators, orientation of minerals and other objects in oriented thin sections and the directional AMS data show that Bambouto caldera, Oku crater and Santa-Mbu caldera are the sources of main PDCs of Bambouto and Bamenda volcanoes. These AMS results have aided us to produce a hazard and risks maps related to potential future pyroclastic flows on these volcanoes. The assessment of risks in these volcanoes was based on populations in the study area, infrastructures (houses and roads) and average income of breeding activity.

Modelbuilder and Unit Hydrograph for Flood Prediction and Watershed Flow Direction Determination at The West Branch of The Little River, Stowe, Lamoille County, Vermont, USA

The West Branch of the Little River in Stowe, Lamoille County, Vermont has been widely studied, and this area is regularly subject to flooding. The West Branch joins the Little River, which flows into the Winooski and drains into Lake Champlain. This area has undergone extensive development as an economic response to the ski resort industry over the past 50 years, and the recreational pathway is on the banks of the river. The Little River is adjusting to the loss of historic floodplain area, channel modifications (straightening and gravel mining), and runoff changes. In this project, a DEM with 10 and 30 meters resolution will be used to determine the watershed area for the outlet point at the south of Stowe for hydrological analysis. This project intends to describe the watershed flow direction with a unit hydrograph that shows when water discharge at the outlet is at its height during a rainfall event and produce the floods prediction map by predicting the nature of flood events to help in planning and responding to flood events effectively using ArcGIS Pro 2.0. The results show the time it takes water to flow to the outlet ranges from 0 seconds (rain that falls on the outlet itself) to over 8 hours and 46 minutes. The amount of water has accumulated, indicating that water will flow at its fastest when funneling toward the outlet point downstream of the town with no exception, indicating that water will flow at its fastest when funneling toward the outlet point downstream of the town.

Determining flow directions in river channel networks using planform morphology and topology

Abstract. The abundance of global, remotely sensed surface water observations has accelerated efforts toward characterizing and modeling how water moves across the Earth's surface through complex channel networks. In particular, deltas and braided river channel networks may contain thousands of links that route water, sediment, and nutrients across landscapes. In order to model flows through channel networks and characterize network structure, the direction of flow for each link within the network must be known. In this work, we propose a rapid, automatic, and objective method to identify flow directions for all links of a channel network using only remotely sensed imagery and knowledge of the network's inlet and outlet locations. We designed a suite of direction-predicting algorithms (DPAs), each of which exploits a particular morphologic characteristic of the channel network to provide a prediction of a link's flow direction. DPAs were chained together to create “recipes”, or algorithms that set all the flow directions of a channel network. Separate recipes were built for deltas and braided rivers and applied to seven delta and two braided river channel networks. Across all nine channel networks, the recipe-predicted flow directions agreed with expert judgement for 97 % of all tested links, and most disagreements were attributed to unusual channel network topologies that can easily be accounted for by pre-seeding critical links with known flow directions. Our results highlight the (non)universality of process–form relationships across deltas and braided rivers.

Analysis of Hydrograph Shape Affected by Flow-Direction Assumptions in Rainfall-Runoff Models

Different approaches for flow-direction determination have been continuously proposed to perform a more realistic simulation of surface runoff, yet the diversity of the existing methods causes significant differences in the extractions of geomorphic parameters as well as the results of rainfall-runoff simulations. In this study, the three most widely used flow-direction methods were separately applied in hydrological models to thoroughly investigate their effects on the simulation output. The results show that the drainage area is a significant factor that affects not only the flow-collecting ability but also the time to peak discharge; however, the definition and calculation of the drainage area become different when the consideration of multiple flow directions is involved in a terrain analysis. This study adopted two area indexes, flow concentration area and flow dispersion area, to understand their consequences in the aspects of the flow volume of simulated hydrograph and the delay of time to peak discharge. The multiple-flow-direction methods show the later time to flow peak and less amount of outflow volume in comparison with the single flow-direction method. By merely extracting two area indexes, a transformation approach is suggested to predict hydrograph shape and to quantify the extent of hydrograph deviations induced by using different flow-direction methods.

A Thermodynamic Model Toward the Comprehension of Ferrous Burden Softening and Melting Using FactSage Macro-Processing

The softening and melting properties of iron-bearing materials play a decisive role in the formation of the cohesive zone, which greatly affects blast furnace gas flow distribution and heat-transfer efficiency. To improve the understanding regarding the evolution of condensed phases during reduction, softening, and melting, a thermodynamic model has been developed using FactSage™ thermodynamic software and macro-processing. The model was constructed using a series of equilibrium stages and splitters to determine flow directions of streams and to consider kinetic inhibitions. For all iron-bearing materials studied, the methodology proposed for modeling was capable of obtaining reduction degrees in very good agreement to its experimental data. The evolution of solid phases was qualitatively comparable to the available literature, with Fayalite, Kirschsteinite, Melilite, and FeO as the main solid phases in equilibrium before slag formation. The comparison between the profiles of the calculated slag mass fraction and the experimental pressure drop showed a close relation between these properties. Moreover, the level of heterogeneity of each raw material may play a significant role in the interpretation of its results.

New Approach in Integrated Basin Modelling: Melen Airborne LIDAR

Airborne LIDAR technology which has an increasing importance in recent years, has entered into the field of application of many disciplines by obtaining fast and highly accurate 3D data. It provides precise topography information with dense point cloud data as well as all details on the surface. Thus, it has become useful in all disciplines associated with space such as cartography, construction, city planning, forest, energy, hydrology, geology, transportation, telecommunications, security, disaster, aviation, and infrastructure. By mounting LIDAR measurement units on aircraft large areas can be measured relatively quickly and cost-effectively. In this study, Riegl Q680i scanner and CCNS5 flight management system were mounted to the aircraft. The digital elevation models; DEM (Digital Elevation Model) and DSM (Digital Surface Model) of the Melen basin, which is located within the boundaries of Düzce and Sakarya was generated using LIDAR point cloud data (.las format) with a point density of 16 points/m2 and also 1/1000 base maps of the basin were produced. In addition, many details such as road, slope, culvert, electricity poles were drawn in accordance with the principles of large-scale map construction regulations and transferred to GIS environment. The Melen basin with an important water storage area, boundaries, basin model, water collection lines, determination of flow directions and connections, the topographic surface of the basin sub-areas, morphology were created using 3D laser point cloud data. So, the digital terrain model of the basin in GIS environment is visualized with linear maps. LIDAR data provides 3D geometric and morphological information that cannot be obtained according to classical methods in this kind of engineering studies. Results suggest that the higher spatial resolution LIDAR-derived data are preferable and can introduce more detailed information about basin hydro geomorphic behaviours.

Analysis of Runoff Aggregation Structures with Different Flow Direction Methods under the Framework of Power Law Distribution

The main purpose of this study is to evaluate the performances of different flow direction methods (FDM) in affecting the runoff aggregation structures within a watershed under the framework of power law distribution. To this end, SFD (single flow direction method), MFD (multiple flow direction method) and IFD (Infinite flow direction method) were applied for determination of flow direction for water particles in Susu river basin, and consequently assessed with respect to the variation of flow accumulation. The results indicate that different patterns of flow accumulation were observed from each flow direction method. Effect of flow dispersion on DEM is strongest with ascending order of SFD, IFD, MFD. However, contribution of individual pixels into outlet follows descending order of SFD, IFD, MFD. Notably MFD and IFD tend to make additional hydrologic abstraction from rainfall excess due to the flow dispersion within the flow paths generated on DEM. This study also investigated the size distribution of flow accumulation which is equivalent to the drainage area generated from the selected FDM. They were fitted to the power law distribution and flow accumulation was recognized as a scale invariance factor based on the parameter estimation for power law distribution by maximum likelihood. It was also noticed that FDM affects the parameter estimation of power distribution where highest exponent was estimated for MFD following by IFD and SFD.

Two Methods to Detect Poorly Sealed Monitoring Wells Using Pumping Test Data in a Confined Aquifer

A correctly installed monitoring well (MW) has its riser pipe sealed against the borehole wall. When a MW is poorly installed, there is some vertical leakage close to the riser pipe, which creates a hydraulic short circuit (HSC). A static water level is measured in the pipe, but it is not the piezometric level in the aquifer, which is unknown. The piezometric error is the difference between the piezometric level and the static level in the pipe. It yields other errors in determining flow directions, travel times, and well capture areas. The groundwater sampled in the monitored aquifer may be viewed as polluted, whereas it is locally polluted by the faulty MW. This article deals with pumping tests in confined aquifers, for which a poorly sealed MW yields biased drawdown and recovery data. A few solutions to detect an HSC have been proposed, using either a slug test or a pumping test coupled with a tracer test. This article presents two new solutions to detect an HSC: they provide first the piezometric error and then the correct values for drawdown data. The data of a pumping test near Moncton, NB, are used to illustrate the two solutions. They show also that the HSC detection helps to solve previous inconsistencies between different sets of values for transmissivity, T, and storativity, S, as obtained by usual methods for pumping and recovery when short-circuiting is ignored or unsuspected.

Bio-inspired all-optical artificial neuromast for 2D flow sensing

We present the design, fabrication and testing of a novel all-optical 2D flow velocity sensor, inspired by a fish lateral line neuromast. This artificial neuromast consists of optical fibres inscribed with Bragg gratings supporting a fluid force recipient sphere. Its dynamic response is modelled based on the Stokes solution for unsteady flow around a sphere and found to agree with experimental results. Tuneable mechanical resonance is predicted, allowing a deconvolution scheme to accurately retrieve fluid flow speed and direction from sensor readings. The optical artificial neuromast achieves a low frequency threshold flow sensing of 5 mm s−1 and 5 μm s−1 at resonance, with a typical linear dynamic range of 38 dB at 100 Hz sampling. Furthermore, the optical artificial neuromast is shown to determine flow direction within a few degrees.

An Automated Processing Algorithm for Flat Areas Resulting from DEM Filling and Interpolation

Correction of digital elevation models (DEMs) for flat areas is a critical process for hydrological analyses and modeling, such as the determination of flow directions and accumulations, and the delineation of drainage networks and sub-basins. In this study, a new algorithm is proposed for flat correction/removal. It uses the puddle delineation (PD) program to identify depressions (including their centers and overflow/spilling thresholds), compute topographic characteristics, and further fill the depressions. Three different levels of elevation increments are used for flat correction. The first and second level of increments create flows toward the thresholds and centers of the filled depressions or flats, while the third level of small random increments is introduced to cope with multiple threshold conditions. A set of artificial surfaces and two real-world landscapes were selected to test the new algorithm. The results showed that the proposed method was not limited by the shapes, the number of thresholds, and the surrounding topographic conditions of flat areas. Compared with the traditional methods, the new algorithm simplified the flat correction procedure and reduced the final elevation increments by 5.71–33.33%. This can be used to effectively remove/correct topographic flats and create flat-free DEMs.

Drainage network extraction from a high-resolution DEM using parallel programming in the .NET Framework

High-resolution Digital Elevation Models (DEMs) can be used to extract high-accuracy prerequisite drainage networks. A higher resolution represents a larger number of grids. With an increase in the number of grids, the flow direction determination will require substantial computer resources and computing time. Parallel computing is a feasible method with which to resolve this problem. In this paper, we proposed a parallel programming method within the .NET Framework with a C# Compiler in a Windows environment. The basin is divided into sub-basins, and subsequently the different sub-basins operate on multiple threads concurrently to calculate flow directions. The method was applied to calculate the flow direction of the Yellow River basin from 3 arc-second resolution SRTM DEM. Drainage networks were extracted and compared with HydroSHEDS river network to assess their accuracy. The results demonstrate that this method can calculate the flow direction from high-resolution DEMs efficiently and extract high-precision continuous drainage networks.

A new depression‐dominated delineation (D‐cubed) method for improved watershed modelling

AbstractPrior to hydrologic modelling, topographic features of a surface are derived, and the surface is divided into sub‐basins. Surface delineation can be described as a procedure, which leads to the quantitative rendition of surface topography. Different approaches have been developed for surface delineation, but most of them may not be applicable to depression‐dominated surfaces. The main objective of this study is to introduce a new depression‐dominated delineation (D‐cubed) method and highlight its unique features by applying it to different topographic surfaces. The D‐cubed method accounts for the hierarchical relationships of depressions and channels by introducing the concept of channel‐based unit (CBU) and its connection with the concept of puddle‐based unit (PBU). This new delineation method implements a set of new algorithms to determine flow directions and accumulations for puddle‐related flats. The D‐cubed method creates a unique cascaded channel‐puddle drainage system based on the channel segmentation algorithm. To demonstrate the capabilities of the D‐cubed method, a small laboratory‐scale surface and 2 natural surfaces in North Dakota were delineated. The results indicated that the new method delineated different surfaces with and without the presence of depressional areas. Stepwise changes in depression storage and ponding area were observed for the 3 selected surfaces. These stepwise changes highlighted the dynamic filling, spilling, and merging processes of depressions, which need to be considered in hydrologic modelling for depression‐dominated areas. Comparisons between the D‐cubed method and other methods emphasized the potential consequences of use of artificial channels through the flats created by the depression‐filling process in the traditional approaches. In contrast, in the D‐cubed method, sub‐basins were further divided into a number of smaller CBUs and PBUs, creating a channel‐puddle drainage network. The testing of the D‐cubed method also demonstrated its applicability to a wide range of digital elevation model resolutions. Consideration of CBUs, PBUs, and their connection provides the opportunity to incorporate the D‐cubed method into different hydrologic models and improve their simulation of topography‐controlled runoff processes, especially for depression‐dominated areas.

A New Analytical Method for Estimating Antarctic Ice Flow in the 1960s From Historical Optical Satellite Imagery

Ice flow velocity is used to estimate ice mass changes in glaciers and is a significant indicator of the stability of the Antarctica ice sheet in global change studies. The existing regional Antarctica ice flow speed maps are usually derived from radar or optical satellite observations of modern satellites since the 1970s. This paper presents a new analytical photogrammetric method for estimating Antarctica ice flow velocity fields by using film-based stereo ARGON photographs collected in the 1960s. The key of the proposed innovative method is a parallax decomposition that separates the effect of the terrain relief from the ice flow motion. An innovative implementation strategy is developed by using a framework that involves key techniques of hierarchical stereo image matching, ice flow direction determination, parallax decomposition, and ice flow speed estimation. This method is applied in the Rayner glacier in eastern Antarctica by using two sets of ARGON images with a two-month interval in 1963. The produced digital terrain model and speed map achieved a ground position accuracy of 61 m and a speed accuracy of 70 m $\text{a}^{-1}$ . A comparison with recent products from 2000 to 2010 shows no significant topographic changes in the study area. Furthermore, the speed around the grounding line remained at the same level, while the speed in the ice shelf front decreased by 73 m $\text{a}^{-1}$ . The ice shelf front advanced by approximately 7 km over more than 40 years. Overall, the observation results indicate favorable conditions for the stability of the Rayner glacier-ice shelf system.

An improved method for single flow direction calculation in grid digital elevation models

AbstractThis paper presents improvements to the global D8 (GD8) method for calculating single flow directions in a grid digital elevation model. Flow directions computed from grid digital elevation models serve as the foundation for much of the analysis and modeling of hydrological processes that are driven by topographic gradients. The literature includes both single flow direction methods, where flow goes to only one downslope cell, and multiple flow direction methods that apportion flow among multiple downslope cells. Among single flow direction methods, the standard D8 method, in which the flow direction is set based on the steepest local slope, results in bias on surfaces that do not align with the grid directions. Efforts to address this problem have led to the development of extended methods that account for elevation values further upslope in determining flow directions. We have identified discrepancies in one such method, GD8, and have examined ways to resolve these discrepancies. An improvement to GD8, named iGD8, is presented that allows replacing a reference cell from which path deviations are accumulated and that considers horizontal path deviation rather than global slope as a flow direction criterion. The improved method is found to be effective in resolving the problems encountered with GD8 and to be more efficient than a previously proposed alternative method (least transversal deviation (LTD) based D8, namely D8‐LTD) that uses recursive searching for the largest upstream area when multiple flow paths converge. The proposed improved GD8 method offers the opportunity for improved analysis and modeling of topographically driven hydrological processes by providing better foundational flow directions for these analyses.

An integrated algorithm to evaluate flow direction and flow accumulation in flat regions of hydrologically corrected DEMs

In order to conduct an accurate hydrological analysis of a watershed, certain conditions need to be understood. Flow direction and flow accumulation are important watershed characteristics that need to be determined before an analysis can be made. Other important characteristics which can be gleaned from analysing the digital elevation model (DEM) of a watershed include channel networks, stream lengths and watershed boundaries. Determining flow direction and flow accumulation is usually carried out in separate steps. Flat regions are types of terrain in raster DEMs without local elevation gradients. Evaluating flow direction and flow accumulation in flat regions using DEMs is a well-known problem in watershed analysis because of the occurrence of problematic parallel flow lines. Calculations also tend to be time-consuming. We have developed an efficient and comprehensive integrated approach to assign flow directions and flow accumulation in flat regions. This approach uses values for non-flat flow accumulation and a maze algorithm with a weight value (MW method) to determine several things: a main flow line through the flat area to the local outlet, an octree tree, and first-in first-out queue structures to calculate flow accumulation. The MW method can be applied to hydrologically corrected DEMs and a single flow path can be provided to resolve all flat areas. To investigate the influence on the topological properties of the channel networks, we used this integrated algorithm to extract three sets of flow accumulation areas from existing DEMs. Using this new integrated method was faster than using the two existing methods and produced continuous channel networks without the occurrence of problematic parallel flow lines.