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6. SUBPROGRAMS A general description of all subprograms in HEC-2 along with a summary of statement numbers and sequence numbers is provided at the beginning of the program (see page 2 of Exhibit 5). The following information is provided at the beginning of each subprogram in the form of comment cards: 1. General function of subprogram 2. Author of subprogram 3. Statement number and program name where subprogram is called 4. Other subprograms called A general description of the function of each subprogram follows: Subprogram H2MAIN calculates water surface profiles for all cross sections for the specified flow conditions. It also calculates approximate critical depths, interpolates cross sections and handles encroachment determinations. Refer to Table 1 for a more complete description of sub- program H2MAIN functions. Subprogram ADDPTS inserts four values of elevation and station into the EL and STA arrays for encroachment stations (STENCL and STENCR). Subprogram BLFLOl determines the water surface elevation at a bridge for low flow control based on either Class A, B, or C flow. The Yarnell formula is used for Class A and the momentum formula is used for Classes Band C. Subprogram BLOCK writes the HEC-2 program version identifica- tion block to provide documentation of program version, error correction and modification status. BLOCK DATA defines and initializes variables when the program is compil ed. Subprogram BWE IR 1 determi nes whether low flow, pressure flow, or combinations of low flow and weir flow or pressure flow and weir flow are controlling. It also determines the energy elevation for all of the types of flow except low flow. lFor a detailed description of subprograms BLFLO and BWEIR, see Training Document No.6, Application of the HEC-2 Bridge Routines, The Hydrologic Engineering Center, June 1974. 19