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3-12 1. The default option,. obtained bY,leaving the control ,word field .,-,.. i ..'j,-,' ,:' ! J.!_:, .\r"~',,' ,-' .-"l /\_ . blank, provides p.J.e.tw<1".croas.:.seG.t4.ons/befor'e processing and printing of the results of routings. It is good practice to obtain the plots with the output to facilitate checking of the results. ~ 2. The plots may be obtained without any other processing by entering ENDPLOT in Columns 61-67. The 80/80 listing of input data and the plots will be printed, but routings will not be done nor any other output printed. The ENDPLOT option can be used to check the cross section data separately prior to processing. 3. The plots will not be made if NOPLOTS is entered in columns 61-67 of the JOB statement. 3.4 WATERSHED SUBDIVISIONS A watershed is subdivided into hydrologically homogeneous subwatersheds. A flood hydrograph is developed for each of these subwatersheds. The attenuation and translation of these hydrographs, due to structures and to floodplain storage and hydraulics, are determined by flood routing. ce Section 2.1 briefly describes these procedures and gives specific references to the applicable portions of NEH-4. The major considerations in delineating subwatersheds are also described in Section 2.l. The sizes of the subwatersheds should be relatively uniform. Unless a hydrograph is needed for a subwatershed that is very small in comparison to the other subwatershed, there is usually little advantage to include it as a separate subwatershed. The difficulty comes from defining the hydrographs with the main time increment. This is discussed under hydrograph development in Section 2.l. For example, a hydrograph developed by combining hydrographs from drainage areas of 0.1, 2.1, and 15.2 square miles is only as accurate as the hydrograph from the 15.2-square-mile areal Therefore, unless ~. '-