1 / 38

Review of Flood Routing

Review of Flood Routing. Philip B. Bedient Rice University. Lake Travis and Mansfield Dam. Lake Travis. LAKE LIVINGSTON. LAKE CONROE. ADDICKS/BARKER RESERVOIRS. Storage Reservoirs - The Woodlands. Detention Ponds.

decker
Download Presentation

Review of Flood Routing

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Review of Flood Routing Philip B. Bedient Rice University

  2. Lake Travis and Mansfield Dam Lake Travis

  3. LAKE LIVINGSTON

  4. LAKE CONROE

  5. ADDICKS/BARKER RESERVOIRS

  6. Storage Reservoirs - The Woodlands

  7. Detention Ponds • These ponds store and treat urban runoff and also provide flood control for the overall development. • Ponds constructed as amenities for the golf course and other community centers that were built up around them.

  8. DETENTION POND, AUSTIN, TX

  9. LAKE CONROE WEIR

  10. Comparisons: River vs. Reservoir Routing Levelpool reservoir River Reach

  11. Reservoir Routing • Reservoir acts to store      water and release through      control structure later. • Inflow hydrograph • Outflow hydrograph • S - Q Relationship • Outflow peaks are reduced • Outflow timing is delayed Max Storage

  12. Inflow and Outflow

  13. Numerical Equivalent Assume I1 = Q1 initially I1 + I2 – Q1 + Q2 S2 – S1 = 2 2 Dt

  14. Numerical Progression I1 + I2 – Q1 + Q2 S2 – S1 1. = DAY 1 2 2 Dt I2 + I3 – Q2 + Q3 S3 – S2 2. DAY 2 2 2 Dt I3 + I4 – Q3 + Q4 S4 – S3 3. DAY 3 2 2 Dt

  15. Determining Storage • Evaluate surface area at several different depths • Use available topographic maps or GIS based DEM sources (digital elevation map) • Storage and area vary directly with depth of pond Elev Volume Dam

  16. Determining Outflow • Evaluate area & storage at several different depths • Outflow Q can be computed as function of depth for Pipes - Manning’s Eqn • Orifices - Orifice Eqn • Weirs or combination outflow structures - Weir Eqn Weir Flow Orifice/pipe

  17. Determining Outflow Weir H Orifice H measured above Center of the orifice/pipe

  18. Typical Storage -Outflow • Plot of Storage in acre-ft vs. Outflow in cfs • Storage is largely a function of topography • Outflows can be computed as function of elevation for either pipes or weirs Pipe/Weir S Pipe Q

  19. Reservoir Routing LHS of Eqn is known Know S as fcn of Q Solve Eqn for RHS Solve for Q2 from S2 Repeat each time step

  20. Example Reservoir Routing ---------- Storage Indication

  21. Storage Indication Method STEPS Storage - Indication Develop Q (orifice) vs h Develop Q (weir) vs h Develop A and Vol vs h 2S/dt + Q vs Q where Q is sum of weir and orifice flow rates. Note that outlet consists • of weir and orifice. • Weir crest at h = 5.0 ft • Orifice at h = 0 ft • Area (6000 to 17,416 ft2) • Volume ranges from 6772 to 84006 ft3

  22. Storage Indication Curve • Relates Q and storage indication, (2S / dt + Q) • Developed from topography and outlet data • Pipe flow + weir flow combine to produce Q (out) Only Pipe Flow Weir Flow Begins

  23. Storage Indication Inputs Storage-Indication

  24. Storage Indication Tabulation Time 2 Note that 20 - 2(7.2) = 5.6 and is repeated for each one

  25. S-I Routing Results I > Q Q > I See Excel Spreadsheet on the course web site

  26. S-I Routing Results I > Q Q > I Increased S

  27. RIVER FLOOD ROUTING

  28. CALIFORNIA FLASH FLOOD

  29. River Routing Manning’s Eqn River Reaches

  30. River Rating Curves • Inflow and outflow are complex • Wedge and prism storage occurs • Peak flow Qp greater on rise limb    than on the falling limb • Peak storage occurs later than Qp

  31. Wedge and Prism Storage • Positive wedge I > Q • Maximum S when I = Q • Negative wedge I < Q

  32. Actual Looped Rating Curves

  33. Muskingum Method - 1938 • Continuity Equation I- Q = dS / dt • Storage Eqn S = K {x I + (1-x)Q} • Parameters are x = weighting Coeff • K = travel time or time between peaks • x = ranges from 0.2 to about 0.5 (pure trans) • and assume that initial outflow = initial inflow

  34. Muskingum Method - 1938 • Continuity Equation I- Q = dS / dt • Storage Eqn S = K {x I + (1-x)Q} • Combine 2 eqns using finite differences for I, Q, S • S2 - S1 = K [x(I2 - I1) + (1 - x)(Q2 - Q1)] • Solve for Q2 as fcn of all other parameters

  35. Muskingum Equations Where C0 = (– Kx + 0.5Dt) / D C1 = (Kx + 0.5Dt) / D C2 = (K – Kx – 0.5Dt) / D Where D = (K – Kx + 0.5Dt) Repeat for Q3, Q4, Q5 and so on.

  36. Muskingum River X Select X from most linear plot Obtain K from line slope

  37. Manning’s Equation Manning’s Equation used to estimate flow rates Qp = 1.49 A (R2/3) S1/2 Where Qp = flow rate n = roughness A = cross sect A R = A / P S = Bed Slope n

  38. Hydraulic Shapes • Circular pipe diameter D • Rectangular culvert • Trapezoidal channel • Triangular channel

More Related