Flood discharges (m3 s-1) calculated for Cottonwood Creek - Arroyo Alamar by rainfall-runoff modeling

 Location \Return period 2 5 10 25 50 100 200 500 1000
 1. Upstream of Morena Dam   309  536  663  91310691294141316331799
 2. Downstream of Morena Dam     34    49    82  129  162  207  230  277  314
 3. Usptream of Barrett Dam   274  446  596  795  9411120121813871509
 4. Downstream of Barrett Dam     36    70   84  140  180  220  321  501  635
 5. Usptream of project reach   245  484  620  85910581227133015031623
 6. Downstream of project reach   277  529  683  92811351308141715961722
 7. Contribution of reach 40117     32    45    63    69    77    81    87    93    99
 8. Adopted design discharge   280  530  680  93011401310142016001720


CONCLUSIONS


  • The postulated channelization with concrete, if accomplished, will convert 3.01 hm3 annually to the surface water. This is 22 percent of the annual groundwater extraction in the Tijuana river basin.

  • The pertinent authorities should select the appropriate return periods for design purposes.

  • According to current regulations, for the delineation of federal zones, the Comisión Nacional del Agua will have to select a return period greater or equal to 10 yr, for which the design discharge will not be less than 680 m3/s.

  • The Instituto Municipal de Planeación (IMPlan) of Tijuana, pending consultation with the pertinent technical authorities, should select an appropriate return period for the design of the channelization project.

  • The interpretation of current regulations permits to establish a return period between 50 and 200 yr for populated agricultural zones. Therefore, in this case the design discharge will not be less than 1140 m3/s and could be as high as 1420 m3/s.

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