Statistical Inference. The energy slope and cross section from the underlying terrain are used to calculate the normal depth. This approach is more time consuming, and requires the user to have a greater understanding of how the flow will separate between openings. The choice of the slope limit in this study was made after analyzing the descriptive statistics of the slope distribution in the analyzed river corridor . ° H = 210. 6. HEC-RAS calculates the energy grade slope by simply solving for S using Manning's equation. Its operation and/or control may be dependent. For improving mitigation, it is important to study the spatial distribution and factors controlling debris flows. Rberg. FUHRMAN Major General, USA Chief of StaffFigure [Math Processing Error] 4. Alaska Department of Transportation & Public Facilities For each inflow hydrograph, at the bottom of the table, enter 0 for EG Slope for distributing flow along BC Line. not enough days to cover the event). 5. 2. HEC-RAS supports networks of channels and is capable of modeling subcritical, supercritical, and mixed flow regime profiles. com Received: from na01-bn1-obe. In the event that the flow rates are not similar, the cross-section geometry or parameters may not be appropriate. What is inequality? An inequality is a mathematical statement that cοmpares twο values οr expressiοns and indicates whether they are equal οr nοt, οr which οne is greater οr smaller. Delta EG ft Change in energy grade line through culvert(s) and bridge(s). Make sure each cell has only one point in it. The flow data can be changed at any cross section within a reach. main window. From the 2D User manual: The Energy Slope is used to compute Normal Depth from the given flow rate and the cross section data (underlying. Known: Temperature distribution in a one dimensional wall with prescribed thickness and thermal conductivity. Anonymous. 4. In real life, the fluid has finite viscosity and there is at least frictional loss in a real flow. A uniform open-channel flow: the depth and the velocity profile is the same at all sections along the flow. 2. It is used in both. Application 1) This Part applies to all plumbing systems covered in this Code. By the no-slip condition, the velocity is zero at y = 0, so the velocity must increase upward in the flow. After your first run you can look at the WSE slope in the area to see if adjustment to you initial estimate is necessary. and. ) To fix errors in the mesh, use the Editing Tools to Add, Delete, or Move points. Guest. A vertical load P is applied to joint C of the truss. 1. In the Flow Hydrograph form, highlight all Flow cells from 0:00 to 48:00 and press Ctrl+V. In Section 2. The elevation of the study area ranges from 383 to 533 m. Delta WS ft Change in water surface through culvert(s) and bridge(s). Distribution methods that are common will include:The lifting line theory is presented in Section 9. The U. Click the “+” button to draw a new profile line on your 2D area. If you put an hydrograph in US Boundary Condition, then don´t forget to provide an initial EG slope. Lets see what they have. Plastic delineators are set along the shoulder. Table 5–2 K-values for the Gumbel extreme value distribution 5–12 Table 5–3 K-values for the log-Pearson type III distribution 5–13 Table 5–4 Discharge peaks, with basic statistics 5–15 Table 5–5 Outlier test K o values, from WRC Bulletin 17B 5–20 Table 5–6 Peak streamflow data at gage 06324500 Powder River 5–24 at Moorhead, MTThe point is that the total head of an ideal Bernoulli flow is conserved. See Grade. In Fig. 5m, the calculated results of Eq (16) with different values of E are shown in Fig 5. O the BC line is diagonal because the amount spent on both goods is less or equal to incomo O the consumer will tind thvat every point along the 13 line is outside the budgot constraint O the consumer will find the highest utility ***** x and y just touch the 12 line Correct o all of the above and the consumer can choose any point on or below the. AquaveoInspect the edge of the 2D Flow Area Mesh for any mistakes in the boundary. (After Fig. 00001 m/s we get: V = 0. 3. We can apply this equation to the scenario in Figure 14. Streamlines indicate local flowto lose both energy (EG slope) and width, while the other zones will likely continue to only narrow. 73%) were larger than those with negative MAR EG (40. At higher Re, the difference in flow. Velocity Distribution. Click OK to assign the flow conditions to the boundaries specified 41. Debris flows are a major geological hazard in mountainous regions. 2. 1. With this length of a line segment calculator, you'll be able to instantly find the length of a segment with its endpoints. 6. Figure 14: Flow hydrograph data window. 001” as the EG Slope for distributing flow along BC Line. A steep of 1 in 40 – 1 in 80 is preferred for house sewers. G. The aim of this study is the analysis of slope stability to investigate possible trigger. Time of concentration (t c ) is the time required for an entire watershed to contribute to runoff at the point of interest for hydraulic design; this time is calculated as the time for runoff to flow from the most hydraulically remote point of the drainage area to the point under investigation. 3. 12. Name the file Flows and click OK. Requires be to “burn” in the manhole into the terrain to meet the minimum cell elevation being equal to or lower than the culvert flowline. Hi all, I have a 2D HEC-RAS (v 5. The hydraulic head h is central to Darcy's Law and the dynamics of water flow in the saturated aquifers. ca. In hydrological and fluvial landforms, the thalweg is a line drawn to join the lowest points along the entire length of a stream bed or valley in its downward slope, defining its deepest channel. Mass movement is caused by gravity. Pressure is force per unit area and increases with depth d in a fluid. Nearshore slope, defined as the cross-shore gradient of the subaqueous profile, is an important input parameter which affects hydrodynamic and morphological coastal processes. Here I’ve named it “Profile 1” and it is stored in the Profile Lines bin. 5. Here a d=3 mm particle is required to have a sliding bed. Delta EG ft Change in energy grade line through culvert(s) and bridge(s). Static resistance determines the power dissipation in an electrical component. June 7, 2016 at 9:55 pm in reply to: Editing the Weir Data #9957. 2. Flow conditions were well documented by making observations from the surface and through the side windows located at the crest brink, mid point, and near the toe of the riprap slope. click on the last point in the line to end the line and bring up a dialog 4. HEC-RAS will snap the line to the edge of the domain. 3. 15) is useful if. 2 m along slope length, which was shown after buffer strip was laid on the slope. . 2. 413ac) roadway, without curbing, contributes to the ditch with a cross slope of 2%. Single looped network. Debris flow, the most extensive and most severe geological hazard along the Karakoram Highway, frequently blocks the Karakoram Highway. Three cone morphotypes include: (a) twin circular and regular cones, (b) twin slightly flat cones with smooth surfaces and irregular contour. 1. In the field of Newtonian Mechanics, there is F net = m • a. Secondly and well hidden: in the check boundary conditions. E. com 2017 Page 1 of 11 SMS 12. direction of flow. Flows in the laboratory can be set up to be very nearly uniform, and outdoors flows like those in long canals are often also close to being uniform. Hydrostatic pressure p is a component of the hydraulic head. Pipeline Profiles: Westcoast or BC Pipeline. Choose any two points along an open channel, for example. The occurrence of landslide has correlations with the atmospheric temperature change. The answer is yes. The BC Energy Regulator (BCER) is a single-window regulatory agency with responsibilities for overseeing oil, gas and renewable geothermal operations in British Columbia. Slope Formula. Although other factors play a role in the type and speed of the mass movement, without gravity, the material would not move, regardless of slope or any other. Plumbing appliance: means any one of a special class of plumbing fixture which is intended to perform a special plumbing function. Also, you don't have to have the first cross section exactly on top of the 2D boundary. Water surface doesn’t necessarily have to though (i. Since the radius is perpendicular to the tangent, the shortest distance between the center and the tangent will be the radius of the. For EG Slope for distributing flow along BC Line:, enter 0. Using the A/D line alone is. “There. Take α to be positive when the flow is below the horizontal and negative when it is above. 1. 1 and 5 and 5 . 13-2CThe inflow boundary conditions for the test problems were chosen so that the function U(x, y, z) = cos(ω (y + z – (t y + t z)x)) is the exact continuous solution of the homogeneous f i 1, i 2, i 3 = 0 problem (2). When running a unsteady flow analysis I got the following error, any thoughts of how to resolve it. The flow hydraulic parameters of EG channel, rill, and interrill sheet flows all increased as rainfall intensity and slope increased. Turn off all background layers to more easily inspect the mesh. G. 2 The depth of the lateral at the property line (measured from the crown of pipe) must be no less than 36 inches and no greater than 48 inches below design grade. This usually occurs from either. The A/D line is an effective tool for spotlighting buying and selling pressure on a security. HEC-RAS 2D Flood Modelling Tutorial - Civil Survey Solutions€¦ · HEC-RAS 2D Flood Modelling Tutorial 8 After importing data into RAS Mapper, it will become available in the HECRASStaff Engineer. 1 Gravity mains must be designed with the following minimum grades: Gravity Main Minimum Grade 8” 0. In the Bailong River Basin, central China, landslides and debris flows are very well developed due to the large differences in terrain, the complex geological. This study simulates rainfall infiltration in a homogeneous soil slope under varying atmospheric temperatures based on water–air. Solution. Layout of Distribution System: Depending upon the layout of various pipes of a distribution system there are four different systems of layout of distribution system as indicated below: 1. g. The locus of points in the specific-head diagram for which the flow is critical is thus a straight line with a slope of (2/3). We can say that the given points A (2, 5), B (24, 7), and C (12, 4) are collinear. Influence of length-diameter on the pressure distribution. General. To use this tool: In the First point section of the calculator, enter the coordinates of one of the endpoints of the segment, x₁ and y₁. Figure 15: Flow hydrograph plot The last required data field you must populate is the EG Slope for Distributing Flow along the BC line, required to distribute the upstream boundary condition across the upstream cells. 24 inches in diameter) in a distribution system may operate up to 200 psi, but the small service lines that deliver gas to individual homes are typically well under 10 psi. e. . En el caso de los hidrogramas o curvas de estación-flujo, deberá definir correctamente los tiempos de inicio y fin del hidrograma, así como el intervalo de tiempo y la pendiente de la línea de energía (EG slope for distributing flow). the Chezy constant is 120. Take the circulation of the vortex to be in the clockwise direction. 1. But uniformity is an abstraction: real flows are never perfectly. This tutorial focuses on the 2D functionality of the model. e. 1. 2. Due to cyclonic rainfall after an abnormally dry summer, North-wales experienced debris flow which caused blockage of road and needed. 14-10 show the same phenomena in a pipe with D p =0. General 1. ] plus 0. com. 1. 1. Application 1. Then, multiply the denominator of the first fraction by the numerator of the second, and you will get: 1400 = 20x. Analyzing Data and Distributions. Always remember this… It is the slope of the energy grade line (EGL). If you put an hydrograph in US Boundary Condition, then don´t forget to provide an initial EG slope for distributing flow along BC line… With, hope you could solve that issue!!! Cheers! Flow Hydrograph dialog. In the Flow Hydrograph form, highlight all Flow cells from 0:00 to 48:00 and press Ctrl+V 39. Imagine a line parallel to BF passing through D. Viewing 3 topics - 1 through 3 (of 3 total) 141 Main Street Pittsfield, ME 049672. Describe the contour-line evidence that supports your answer. The term. 3 suggests the following expression: ΔV = ∫w(x)dx. Using the method of double integration, determine the slope at support A and the deflection at a midpoint C of the beam. Further information on the permitting process can be obtained from the local health authority. 0 N. Sometimes flow doesnt just appear at the channel of the stream and if you enter anything like 0. This manual is intended as a guide for designing and constructing levees and not intended to replace the judgment of the design engineer on a particular project. For EG Slope for distributing flow along BC Line, type in 0. What is the equation of the line that is parallel to the given line and passes through the point (−4,−6 )? y = −6. When I right-click on the boundary condition using RAS Mapper, the time. 0 m to 10 m. During low flow conditions, the flow comes over the flat concrete crest and dives down into the riprap layer. madelineh. The development of the hydraulic grade line is a last step in the overall design of a storm drain system. First, let’s briefly review why you may need to interpolate cross sections in HEC-RAS. I used 2D equation. Figure 5-5. Although this method is a deformation method like the slope-deflection method, it is an approximate method and, thus, does not require solving simultaneous equations, as was the case with the latter method. Best Practice #4: Properly Remove Air and Condensate at End of Steam Line. 1 5. UNSTEADY FLOW DATA. Guest. Click on the ‘BCLine: Chashma_Barrage’ and select ‘Flow Hydrograph’ as Boundary Condition. A flowline is a line through the center of a channel reach or a water body, which defines the main direction of flow. The flow in thisPrecipitation Intensity. 2 Soil Infiltration Capabilities. Download DEMs The next thing you need is terrain data. E. A long diagonal line is passing through the middle of line segment BC. Download Free PDF. Figure [Math Processing Error] 1. For other plots, the subsurface flow was not more than one-third of the infiltration, indicating that the infiltration dominated the supply to soil water along the slope. Reply To: EG Slope for distributing flow along BC line Home › Forums › HEC-RAS Help › EG Slope for distributing flow along BC line › Reply To: EG Slope for distributing flow along BC line July 29, 2016 at 10:38 pm #10000 6. The side slopes are 3:1. The washout by slope flow along long-distance oil & gas pipelines is a common geological hazard that occurs when pipelines pass through the alluvial-proluvial fan section of mountain piedmont. Anonymous. 4. HEC-RAS. 0 m3/s to 1000 m3/s and at D/s, depth will rise linearly from dry state i. Dead-End System or. The momentum equation for variable mass flow with a variable exchange coefficient and variable friction coefficient was developed by using the momentum conservation method. There is a lovely formula: |𝑎𝑥₁ + 𝑏𝑦₁ + 𝑐|/√ (𝑎² + 𝑏²) This formula tells us the shortest distance between a point (𝑥₁, 𝑦₁) and a line 𝑎𝑥 + 𝑏𝑦 + 𝑐 = 0. In this case, I’m not sure what the problem is without seeing the model firsthand, but the EGL indicates localized errors. (where V is the velocity of the groundwater flow, K is the hydraulic conductivity, and i is the hydraulic gradient). Use an electronic buried drain line locator to find the D-box23. 28% of the total area between gullies (Zhang, 1991). Flow Area = Looking at the cross section of the channel, the area of the flow. 0 (February 2016) 56 Figure 109 ‐ Add TR‐66 breach hydrograph data to the upstream boundary condition EG Slope for distributing flow along BC Line – 2D. 1 Van Genuchten model. PF 1 stands for profile flow 1. an existing creek abutting an existing car park being considered for. Secondly and well hidden: in the check boundary conditions. Steady versus Transient Heat Transfer Heat transfer problems are often classified as being steady (also called steady- state) or transient (also called unsteady). Aqueduct is a significant watercourse which carries water from a source to the far distribution point. 23 Cos(1. 6 to 1. perform one-dimensional (1D) steady flow, and 1D and two-dimensional (2D) unsteady flow river hydraulics calculations. HEC-RAS is an integrated system of software, designed for. #1- Covariance/Variance Method. Click on Save > Unsteady Flow Data. Internal waves are ubiquitous in the stratified ocean interior. For an opaque surface, the absorptivity () α , transmissivity () τ and reflectivity () ρ are related by the equation : (A) α ρ τ + = (B) 0 ρ α τ + + = (C) 1 α ρ + = (D) 0 α ρ + = MCQ 7. That means. Shift in Terrain Data. If you have not previously registered and would like to comment or post on the forum, please click here to register. Conventional reciprocating piston pump distributing flow (RPPDF) systems have the disadvantages of a loose structure and low volumetric efficiency, as well as affected positively by the operating frequency. I typically estimate the EGL slope from the terrain slope in the area where the flow is expected to be most concentrated. It's related to the slope of the channel bottom and the velocity together. The frequencies ω = 8π for a 64 3 grid and ω = 16π for a 128 3 grid. But at their core, is a passion for solving challenging and impactful problems that strive to bring us closer to a renewable future. 5, Computer code: Prandtl’s lifting line method. Cross Sections should be selected early on in your project to adequately define changes in. A parallelogram, the diagonals bisect each other. 10) Where S is the water surface slope. 27%). 1). 5 cm [1 in. 03; slope angle = 1. The set of all points in a plane, the sum of whose distances from two fixed points in the plane is constant is an ellipse. 1). What is the length of the one of the braces, to the nearest tenth of a centimeter? Enter your answer as a decimal in the box. The easiest way to get this is to assume the. ) bora along a cross section through Senj, Croatia are shown in Fig. Turn off all background layers to more easily inspect the mesh. Where testing determines that the infiltration rate of the subsurface soils is less than inch (12. During the Select the Profile Lines tab. Divided Flow Approach. 01 Flood Breach Analysis Using ArcMap & HEC‐RAS 5. 13m. CHAPTER 7 HEAT TRANSFER GATE Previous Year Solved Paper For Mechanical Engineering. Best Practice #1: Choose Trap Locations Carefully. When looking at output, however, the friction slope represents an average between 2 cross sections and is exactly the friction slope that is used to compute friction. For a rhombus, where all the sides are equal, we've shown that not only do they bisect each other but they're perpendicular bisectors of each. A carpenter builds a rectangular bookcase that is 120 cm long and 62 cm tall. e. The relatively steep distance-decay relationship (slope = −0. In the field of Wave Mechanics, there is v = f • λ. Radiocarbon age dating showed that slope failures are early to mid-Holocene. A series of laboratory experiments were conducted under slope gradients of 5°, 10°, 15°, and 20° and flow rates of 2, 4, and 8 L min−1 to measure the water flow velocities over eroding and non-eroded loess soil slopes, under saturated conditions by using electrolyte tracing. , 2011). Abaqus/Standard. There are also pressure forces acting parallel to the flow direction on the upstream and downstream faces of the free body. • The 20’ x 900’ (0. In the field of Modern Physics, there is E = m • c 2. We are widely respected for conceptual and final design work of fish passage facilities and biological assessments relating to fish. Arterioles distribute blood to capillary beds, the sites of exchange with the body tissues. BC ∥ AD and CD ∥ BA. 23] Certified Backflow Assembly Tester. 1: A uniform open-channel flow: the depth and the velocity profile is the same at all sections along the flow. Name the file Flows and click OK. The optimal performance of the cardiovascular system, as well as the break-down of this performance with disease, both involve complex biomechanical interactions between the heart, conduit vascular. com Received: from na01-bn1-obe. As a result, changes in channel geometry, slope, or flow can affect the results of an HEC-RAS model for a considerable distance upstream. Slope = The is just the slope of the above Grade Line. This is a standard deviation value and is generally considered accurate with datasets of 20 or. The slope of BA is . Water flows down a uniform channel with a slope of . A streamline is a line drawn . nabble. In nearly all instances, it ends at its seaward edge with an abrupt drop called the shelf break . Good practice is to size the pipe on a low steam velocity of not more than 15 m/s, to run the line at a slope of no less than 1:40, and install the drain points at not more than 15 metre intervals (see Figure 10. 40. What value did you use for the EG Slope for distributing flow along the BC Line? The smaller the value the more flow will spread out across your BC line and cause the flooding you see. Our water resource engineering team is composed of technical experts in hydrology, hydraulics and civil engineering who interact with our fisheries, aquatic and terrestrial scientists to provide cost-effective, ecosystem-based solutions. Similarly, in the Second point section, input the coordinates' values of the other endpoint,. 1. 3m, the diameter of the holes d = 0. There is more than one option, however, for downstream boundary condition. Secondly and well hidden: in the check boundary conditions. Then multiply the numerator of the first fraction by the denominator of the second fraction: 1400 =. 7 mm pipes used to feed individual outlets within a building. 500 kV line 65 m 45 m 30 m 20 m 10 m 287 kV line 230 kV line 138 kV line 69 kV line Typical transmission corridor widths Low Zone Step 4: Locate your geographic region. Schematic: Assumptions: (1) steady-state conditions, (2) one –dimensional heat flow, (3) constant properties. Next, save the unsteady flow data. 7 Pada Boundary Condition pilih Flow Hydrograph Use Simulation Time 1 Hour pada “Data time interval” Masukka hidrograf banjir rencana masukkan nilai slope pada “EG Slope for distributing flow along BC Line” OK Catatan: hidrograf banjir yang dimasukkan adalah hasil perhitungan HSS DAS, kala ulang 100 the Flow Hydrograph form, highlight all Flow cells from 0:00 to 48:00. The stream function (see Section 2. 3) the flow is irrotational. Speed limit is 30km/h, but it is traffic controlled 24 hours per day/7 days per week, and traffic speeds through the site are very low at all times. On the grid, construct a topographic profile along line BC. Participant. G. Because of the emergency management implications of post-wildfire work, decision makers are often looking to understand their communitWhat value did you use for the EG Slope for distributing flow along the BC Line? The smaller the value the more flow will spread out across your BC line and cause the flooding you see. At every point along this line, the liquid boils to form a gas and the gas condenses to form a liquid at the same rate. Then the distribution of depth-averaged velocity along the lateral section will be the line joining of individual depth-averaged velocities at each vertical. Septic System Design BC requires the use of a distribution method that ensures an even flow is achieved from the septic tank to the drain field. The road is super elevated away from the fill slope as it is a curve to the left, so in icy conditions, traffic will not slide towards the fill slope. Remove that BC line and make sure the 1D reach is connected to the 2D Area. 7 Pada Boundary Condition pilih Flow Hydrograph Use Simulation Time 1 Hour pada “Data time interval” Masukka hidrograf banjir rencana masukkan nilai slope pada “EG Slope for distributing flow along BC Line” OK Catatan: hidrograf banjir yang dimasukkan adalah hasil perhitungan HSS DAS, kala ulang 100Home › Forums › HEC-RAS Help › EG Slope for distributing flow along BC line › Reply To: EG Slope for distributing flow along BC line. In particular, on July 16, 2006, shallow landslides occurred in the study area (Fig. June 29, 2016 at 4:51 pm #9976 The energy grade line should always slope downhill. NACA 4412 Airfoil 4 digit code used to describe airfoil shapes 1st digit - maximum camber in percent chord 2nd digit - location of maximum camber along chord line (from leading edge) in tenths of chord 3rd and 4th digits - maximum thickness in percent chord NACA 4412 with a chord of 6” Max camber: 0. October 9, 2018 at 7:57 pm #11818. WARNING! Solution Solver Failed. 7. 332. Started by: Rberg in: HEC-RAS Help. The complex is affected by a MOW flow filament that descends along a channel, warming the deposits and thereby triggering the destabilization of hydrates and generating several pockmarks. Two-dimensional capabilities were added to the program in version 5. During theSelect the Profile Lines tab. )The moment distribution method of analysis of beams and frames was developed by Hardy Cross and formally presented in 1930. Dist Center R ft Distance from center of channel to right encroachment. Next, save the unsteady flow data. Design of a Distribution System 3. 3. of Division A. Based on the methods of field measurement, indoor statistical analysis and theoretical research, this paper discusses the relationship between the four types of debris flow along the Karakoram. (See Article 1. at a given instant in time . !!! 1D, 2D, or a mix? Make sure your initial and boundary conditions keep all cross sections wetted. Open the HEC-RAS project with the desired model and results. Equation 4. You can investigate this by building. 3 Design Considerations. HEC-RAS单纯的二维模拟参数不多，但存在一些参数是一维和二维共用。. (See A-2. 0. On the Loess Plateau, the occurrence of EGs is usually. 5 (150%) By changing the pipe,. varied flow at the point where the jump condition for the sequent depths is correct. 9 gpm, we’re off the scale. Civil Survey ApplicationsImporting and Editing Flow Data Enter the flow editor using Edit/Steady Flow Data from the main project window. In Version 5. Just get it close so that the conveyance distribution over the cross section is close to the conveyance distribution over the 2D edge that is connected. 6. In hydrologic and hydraulic applications, river slope is a key parameter. 0 (February 2016) 56 Figure 109 ‐ Add TR‐66 breach hydrograph data to the upstream boundary conditionEG Slope for distributing flow along BC Line – 2D. For unsteady flow, HEC-RAS solves the full, dynamic, 1-D Saint Venant Equation using an implicit, finite difference method. The last required data field you must populate is the EG Slope for Distributing Flow along the BC line, required to distribute the upstream boundary condition across the upstream cells. Given two integer points (x1, y1) and (x2, y2). dr dt. 5. If you put an hydrograph in US Boundary Condition, then don´t forget to provide an initial EG slope for distributing flow along BC line… With, hope you could solve that issue!!! Cheers! 4 Create the 2D Flow Area The 2D Flow Area will go from just downstream of the Dam to the confluence with West Branch Susquehanna River and will include a portion of Marsh Creek, Beech Creek, and Fishing Creek tributaries. Example #3. Because of the emergency management implications of post-wildfire work, decision makers are often looking to understand their communit Home › Forums › HEC-RAS Help › EG Slope for distributing flow along BC Line – 2D › Reply To: EG Slope for distributing flow along BC Line – 2D October 12, 2018 at 6:38 am #11821 Rberg For this example, we’ll use HECRAS to undertake a 2D flow analysis of. What We Do. Road drainage design has as its basic objective the reduction and/or elimination of energy generated by flowing water. 2. g 121 F(η) dimensionless function uU= ∞ UF. e. 1 二维计算参数（2D Flow Options）. The thalweg thus marks the natural direction (the profile) of a watercourse. For this example, we’ll use HECRAS to undertake a 2D flow analysis of. or gradually varied flow.