def calc_overland_flow(precipExcess, satFrac):
    """ Calculate overland flow (surface runoff)

    Parameters
    ----------
    precipExcess : int or float
        Excess precipitation [mm day^-1]
    satFrac : float
        Saturated fraction of the unsaturated zone
    Returns
    -------
    overlandFlow : float
        Overland flow (surface runoff) [mm day^-1]
    """

    overlandFlow = precipExcess * satFrac

    return overlandFlow