• -1 means the gradient is more than 3° and the creek is designated as mountain/steep creek
• 0 means the gradient is less or equal to 3° and the creek is not designated as mountain/steep creek

• Low:
  • Dense vegetation, especially along the main stream channel flowing over the fan
  • Previous channels, lobes or levees are difficult to discern from the surrounding fan environment
  • Mature vegetation (coniferous forest greater than 50 years old) is dominant across the fan
• Moderate:
  • Main stream channel may have sparse or inconsistent vegetation coverage
  • Previous channels, lobes or levees are visible but may be partially or fully vegetated
  • Immature forest vegetation (deciduous or mixedwood forest and shrubs less than 50 years old) is present in swaths across the fan, specifically near previous or active channels.
• High:
  • Fresh deposits or eroded areas along and within the main stream channels flowing over the fan
  • Clear distinction of previous channels, lobes or levees compared to adjacent fan environment
  • Pioneer vegetation (lichen, moss, graminoids and shrubs less than 2 years old) or extents of bare sediment are present in and around the main channel of the fan

Watershed is the land area that drains rainfall and snowmelt to creeks, streams, and rivers, and eventually to outflow points such as reservoirs, lakes, bays, and the ocean.

Watershed length is the longest straight-line distance from the fan apex to the most distant point on the watershed boundary.

Watershed is the land area that drains rainfall and snowmelt to creeks, streams, and rivers, and eventually to outflow points such as reservoirs, lakes, bays, and the ocean.

Watershed relief is the difference between maximum and minimum elevation of a watershed.

Melton Ratio is a dimensionless ratio defined as the watershed relief divided by the square root of the watershed area. Melton ratio along with other watershed parameters generally defines the dominant process or hazard in a fan, for example, debris flows, debris floods and low debris flood.

Basin sediment supply condition presented as “supply-unlimited” and “supply-limited” basin.

• Supply-unlimited basins typically contain erodible deposits and/or landslides that continuously charge the channel with sediment and debris. These will trigger an event every time a hydro-climatic threshold is exceeded. Most debris-flood prone watersheds are supply-unlimited due to their alluvial beds in which large amounts of loose debris is stored.
• Supply-limited basins are typically rocky or heavily vegetated, with fewer sediment and debris sources for the main channel. These require time to accumulate debris before a rainfall and/or snowmelt event can trigger a debris flow.

Watershed is the land area that drains rainfall and snowmelt to creeks, streams, and rivers, and eventually to outflow points such as reservoirs, lakes, bays, and the ocean.

Watershed activity level is based on the recentness of channel deposits, evidence of erosion and whether the watershed sediment supply is limited or unlimited.

• Low: no recent channel deposits and mature tree growth to the active channel bank, the tree line is close to the watershed peak elevations. Supply-limited watershed, mostly bedrock controlled main channel with little alluvium present in the main channel or available to the few tributaries within the watershed.
• Moderate: deciduous tree bordering active channel, 1/3 of watershed above tree line, some active sediment sources along main channel. Supply unlimited watershed, main channel varies in width and is a mixed bedrock-alluvial channel.
• High: deciduous trees border the active channel, 2/3 of the watershed is above the tree line, numerous highly active sediment sources along main channel (i.e. debris slides, debris avalanches, raveling in lacustrine, glacio-fluvial, or morainal sediments. Supply unlimited watershed with a wide and debris-rich alluvial main channel.

• Low: poorly defined source areas; absence of fresh landslide scars, debris flows or channel deposits, low Active Area Ratio (a ratio of the total area of sediment sources to the total basin area), supply-limited watershed.
• Moderate: well-defined source areas; presence of some fresh landslide scars in soil or rock and some channel deposits, moderate Active Area Ratio, usually supply-limited watershed.
• High: numerous, well-defined, actively producing source areas in tributaries and along main channel; channel choked with debris, abundant fresh landslide scars in soils and rock, fresh channel deposits, high Active Area Ratio, supply-unlimited watershed.

Surface evidence for previous avulsions were based on vegetation evidence and the presence of relict channels, lobes, and deposits on the fan surface. These features can be detected, if present, on LiDAR hillshade; interpretations are less certain for areas without LiDAR coverage.

• Poor: relic channels (abandoned channels) on fan surface exist but are vegetated and difficult to discern.
• Moderate: relic channels on fan surface are clearly visible; swaths of young (<50 year) deciduous or coniferous vegetation exist in previous avulsion paths.
• Strong: obvious fresh avulsion paths exist, swaths of bare sediment or low (<2 year) pioneer vegetation exist on previous avulsion paths.

Channel confinement level is the degree to which stream channels are limited in their ability to move laterally. Channel confinement level is based on estimated bank height and the presence of areas where confinement could be reduced during an event, for example, channel bends, changes in channel gradient, and channel constrictions at road crossings.

• Low: minor or transient channel banks visible on LiDAR hillshade (likely <5 m deep), or obvious presence of locations where confinement could be reduced during an event (e.g. channel bends, changes in channel gradient, channel constrictions).
• Moderate: obvious (likely 5-15 m deep) channel banks on LiDAR hillshade, some presence of locations where confinement could be reduced during an event (e.g. channel bends, changes in channel gradient, channel constrictions or areas of potential blockage).
• High: obvious (likely>15 m deep) channel banks on LiDAR hillshade, no obvious locations where confinement could be reduced during an event (e.g. channel bends, changes in channel gradient, channel constrictions).

• Debris flow: a dense, fast-moving, channelized flow of water and debris, similar to wet concrete that poses a hazard to infrastructure and those living in mountainous environments. Debris flows contain a high percentage (greater than 30%) of sediment by volume and result in rapid sediment transport. The moving sediment controls the flow behaviour of these events.
• Debris flood: a flood containing a moderate percentage (up to 30%) of sediment by volume. It is distinguished from a debris flow in that water controls the flow behavior as opposed to the sediment.
• Low debris flood: a flood with a low proportion of debris compared to debris floods. Low debris flood typically occur on creeks that are not steep.

Hazard chance is the probability of a hazard occurrence within the watershed and fan. Hazard chance estimates are based on surface evidence of geomorphic activities. An active fan and watershed will have a higher relative hazard chance.

Hazard chance are represented as Low, Medium and High based on their return period, also known as a recurrence interval or repeat interval:

• Low: more than 100 years
• Moderate: 30 to 100 years
• High: less than 30 years

Avulsion is the sudden change in stream channel position in a fan due to partial or complete blockage of the existing channel by debris.

Avulsion susceptibility is the potential for avulsion. It is based on the channel confinement level and evidence of previous avulsions. It can be assessed through vegetation type and condition, presence of abandoned channels, and deposits on the fan surface.

• Low: fans with poor surface evidence or record of previous avulsions and having moderate to high channel confinements were assigned to the low avulsion susceptibility category.
• Moderate: fans with moderate surface evidence of avulsions and having moderate channel confinements, or fans with poor surface evidence of avulsion and low channel confinement were assigned to the moderate avulsion susceptibility category.
• High: Fans with strong surface evidence of avulsion events with moderate to low channel confinement, or fans with moderate surface evidence of avulsion events with low channel confinement were assigned to the high avulsion susceptibility category.
• A combination of higher channel confinement and higher or moderate evidence of avulsion is considered unlikely.

Landslide dam is an earthen dam created when a landslide completely blocks a stream or river. Outbreak flood is the flood created by the landslide dam failure.

Outbreak floods susceptibility is the potential for landslide dam outbreak floods. It is based on evidence of past landslide, landslide dams, and presence of channel sections that are susceptible to blockage (i.e., channel constrictions).

• Low: absence of evidence of larger landslides reaching the valley floor, no evidence of previous landslide dams.
• Moderate: no evidence of previous landslide dams, presence of potential landslides with the potential to travel to the valley floor, presence of channel sections potentially susceptible to blockage (e.g. channel constrictions).
• High: evidence of past landslide dams, presence of large landslide scars with the potential to travel to the valley floor, channel sections potentially susceptible to blockage (e.g. channel constrictions).

Bank erosion is the removal and transport of riverbank material downstream. Erosion causes channel widening and can be severe during debris flow and debris flooding events.

Bank erosion susceptibility: the potential for bank erosion. Bank erosion susceptibility is based on signs of previous channel widening. In general, the higher ratings applied to channels with moderate or lower levels of confinement.

• Low: no visible evidence of channel widening, or unconfined channel where channel change is most likely to occur via avulsion.
• Moderate: signs of some channel widening (up to 2 times “normal” width, i.e. equilibrium channel width.)
• High: surface signs of previous channel widening > 3 times the “normal” width, i.e. equilibrium channel width.