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<br />(4) Channel encroachments may be included in the analysis by using <br />variables on card X3 (third card for cross section). ENCFP is used to specify <br />a width between encroachment areas which is centered in the channel midway <br />between the left and right bank stations. This width will be used for each <br />cross section until another value of ENCFP is entered. Another method for <br />specifying encroachments is to enter the station and elevation of the encroach- <br />ment as variables STENCL and ELENCL on the left and STENCR and ELENCR on the <br />right. If only the station is required the elevation should be omitted and <br />it will be assumed to be very high. Other methods are presented in Exhibit 9A. <br /> <br />(5) The existing cross section as described by the GR cards can <br />be modified due to the excavation of a trapezoidal channel by the use of <br />subroutine CHIMP which is called by the CI card. The GR points are modified <br />due to the excavation. but no fill is used. The bank elevations and stations <br />are modified if the channel daylights outside the original bank stations. <br />If the alignment of the excavated channel is such that two separate channels <br />exist. the division between overbank and channel will be based on the exca- <br />vated channel. and the old channel will be considered as overbank (no fill). <br />It may be necessary to change the reach lengths for this case. <br /> <br />k. Multiple Profiles. Where it is desired to compute several profiles <br />using the same cross sectional dsta. variable NPROF on card J2 is used. For <br />the first profile. NPROF is set equal to 1 and all cross section cards are <br />read in. For all remaining profiles NPROF equals the profile number. i.e.. <br />2. 3. 4 ..... and only cards Tl. T2. T3. Jl and J2 are required (cards NC <br />through EJ are omitted). If NPROF is set equal to 15 for the last of two <br />or more profiles. a summary printout is called for which will provide a <br />concise summary of results for all profiles for each cross section. For a <br />single job NPROF can be left blank. or. if the summary printout format for <br />the single job is desired. set equal to -1. <br /> <br />1. Cross Sections with Levees. <br /> <br />(1) Levees require special consideration in computing water surface <br />profiles because of possible overflow into areas outside the main channel. <br />Normally the computations are based on the assumption that all area below the <br />water surface elevation is effective in passing the discharge (IEARA - 0). <br />However. if the water surface elevation is less than the top of levee elevation. <br />and if the water cannot enter the ovetbanlaoupstream or downstream of that <br />cross section. then all flow are~n these overbanks should not be used in the <br />computations. Variable IEARA oDCcard X3 is used for this condition. By <br />setting lEARA equal to 10 the program will consider only flow confined by the <br />levees. unless the water surface elevation is above the top of one or both <br />sides of the levee. in which case flow area or areas outside the levee will <br />be included. When the water surface elevation is close to the top of the <br />levee. it may not be possible to balance the assumed and computed water surface. <br />elevations due to the changing assumptions of flow area when just above and <br />below the levee. When this condition occurs a note will be printed that states <br />that the assumed and computed water surface elevations for the cross section <br /> <br />6 <br />