The role of infrequently mobile boulders in modulating landscape evolution and geomorphic hazards

A landscape’s sediment grain size distribution is the product of, and an important influence on, earth surface processes landscape evolution. Grains can be large enough that motion of a single grain, infrequently mobile in size-selective transport systems, constitutes or triggers significant geomorphic change. We define these grains as boulders. Boulders affect evolution; their dynamics effects on form have been focus substantial recent community effort. review progress five key questions related to how boulders evolution unglaciated, eroding landscapes: 1) What factors control boulder production hillslopes subsequent downslope distribution? 2) How do hillslope long-term evolution? 3) fluvial river channel shape? 4) boulder-mantled channels interact set boulder-influenced landscapes? 5) contribute hazards, might improved understanding used for geohazard mitigation? are produced by landsliding, rockfall, and/or exhumation through critical zone. On dominated local transport, soil such sets steady-state hillslopes. Hillslopes nonlocal less likely exhibit controls morphology rapidly transported toe. Downslope delivers rivers where act roughness elements change flow hydraulics efficiency erosion transport. Over longer timescales, adjust geometry accommodate supplied from adjacent erode at baselevel fall rate given distribution. The delivery channels, paired with response delivery, drives channel-hillslope feedbacks transient landscapes. At event scale, landscapes represent component hazards mitigated rates associated mobility. Opportunities future work primarily entail field-focused data collection across gradients boundary conditions (tectonics, climate, lithology) goal one self-organization.