Pacific Region Example
Top of bank (TOB): the points closest to the
boundary of the active floodplain of a lake, stream, or other body of
water where a break in slope of the land occurs such that the grade beyond
the break is flatter than 3 (horizontal) to 1 (vertical) at any point for
a minimum of 15 metres measured perpendicularly from the break. Where
banks are not well defined (e.g. in the case of lakes, wetlands or ponds),
the top of the bank is equivalent to the high water mark (HWM) or active
floodplain, whichever is greater.
(Ordinary) High Water Mark (HWM): the visible
high water mark of any lake, stream, or other body of water where the
presence and action of the water are so common and usual and so long
continued in all ordinary years as to mark upon the soil of the bed of the
lake, river stream, or other body of water a character distinct from that
of the banks, both in vegetation and in the nature of the soil itself.
Typical features may include, a natural line or "mark" impressed on the
bank or shore, indicated by erosion, shelving, changes in soil
characteristics, destruction of terrestrial vegetation, or other
distinctive physical characteristics.
Active Floodplain: an area adjacent to a
lake, stream or other body of water that is periodically flooded, ranging
from rare, severe storm events to flows experienced several times a year.
For example, a "10 year floodplain" would include the area of inundation
that has a frequency of occurring, on average, once every 10 years. It
includes lands at the same elevation as areas with evidence of moving
water, such as active or inactive flood channels, recent fluvial soils,
sediment on the ground surface or in tree bark, rafted debris, and tree