Field measurement of the initiation of large bed particle motion in Blue Creek near Klamath, California

Abstract

More than two-thirds of the field measurements of bed velocity necessary to initiate motion of coarse natural particles whose size, shape, specific gravity, and orientation angle were known agree within 20 percent of those velocities predicted from theory. The theory is based on balancing turning moments of the fluid forces of drag and lift with the resisting moment of the submerged particle weight. Initial motion seems to depend more on size and shape than on specific gravity or orientation angle. In fact, shape differences almost completely compensate for differences in specific gravity ranging from 2.65-3.00 and orientation angles ranging from 0°-25°. Bed velocities necessary to initiate motion of coarse bed material in Blue Creek are equaled or exceeded about 5 percent of the time. This fact and changes in channel topography and cross-sectional area emphasize the ability of perennial mountain streams to transport coarse bed material frequently.

Evaluation of tsunami flooding using geomorphologic evidence

“…The karstification and fracturation degree of sloping rocky coasts conditions the value of the Manning number to become approximately 0.052. In the coastal area of Apulia, in the proximity of the studied areas, there is a considerable variation in local roughness, hence these areas have been subdivided in fixed buffers with a constant length and inland depth: the buffers in Torre Squillace are 25 m × 90 m, while in Torre Sant'Emiliano are 100 m × 300 m. This is an approximation useful to simulate open channel flow (Manning, 1891;Helley, 1969). The percentage of land and soil utilisation, inside every buffer, has been assessed by using the Corine Land Cover 2000 land-use class features (European Commission, 1994) in order to obtain the mean evaluation of the Manning number.…”

Block and boulder transport in Eastern Samar (Philippines) during Supertyphoon Haiyan

“…We applied boulder-specific values for C d , coefficient of drag (Table 2), by calculating boulder-specific shape factors (Corey, 1949) and taking the appropriate C d values from Fig. 3 in Helley (1969), as suggested by Noormets et al (2004). For C l , coefficient of lift, we used 0.178 according to previous studies (e.g.…”

“…3), maximum significant wave heights of ∼ 4-5 m and ∼ 5-6 m are inferred for site ESA and for Hernani, respectively, from the Delft3D model pre- a -V abc of ESA 9 was corrected to V DGPS using a conservative value of 0.6, which was empirically calculated for the similarly shaped boulder ESA 7; b -Corey shape factor and appropriate C d values according to Corey (1949), Helley (1969: Fig. 3), and Komar and Reimers (1978).…”

Sedimentology of rocky shorelines: 3.

“…Drag force is given by (Bradley and Mears, 1980), where the drag coefficient, C D =1.95, has been taken from the graph given in Fig. 3 in Helley (1969) based on the shape factor. A n is the area of the particle projected normal to the flow, q f is mass of unit volume of the water, and u is flow velocity.…”

“…Major changes in the megaclast locations on the platform could be recognized, however. Megaclasts were rearranged between 1940and 1950, 1952and 1962, and 1969and 1971(Noormets et al, 2002. Although relocation of single megaclasts is obvious at various times, the group as whole has remained relatively stable.…”