numpy
# matplotlib  # (optional) to create plots of the cross section
# sympy  # (optional) to solve equations - currently solved numerically with scipy
# swmm-api  # (optional) to export cross-section as curve in Input file CURVES section
# scipy  # (optional) extends functionality / length, area, h_T, intersection point
# ezdxf  # (optional) to read .dxf files