def split_reaches(list_of_reaches, new_reach_pts):
    """splits l into sections where new_reach_pts contains the starting indices for each slice"""
    new_reach_pts = sorted(new_reach_pts)
    sub_list = [list_of_reaches[i1:i2]
                for i1, i2 in zip(new_reach_pts, new_reach_pts[1:])]
    last_index = new_reach_pts[-1]
    sub_list.append(list_of_reaches[last_index:])
    return sub_list