def calc_time_factor(start_breach, end_breach):
    """
    calculates the fraction of island height to be reduced during simulation
    :param start_breach: start time (island should be inundated here)
    :param end_breach: end time
    :return: return the timing ratio
    """
    total_time = abs(end_breach - start_breach)
    num_time_steps = total_time / 7.5  # current run timesteps every 7.5 seconds or so
    tf = 1 / num_time_steps  # calculate how many steps it takes to reach 100% breach
    return tf