STUDY OF THE ROUGHNESS CHARACTERISTICS OF PLANT SPECIES IN CALIFORNIA RIVERS By U.C.Davis J.Amorocho Hydraulics Laboratory

The objectives of this study: 1. to determine the hydraulic roughness (Manning’s n) associated with each of California native plant species under various flow conditions (from low to high flows), 2.to compare these roughness values to bare soil roughness conditions that may be present on the floodplains in river reaches where these plants occur, 3.to quantify the response of stems of known density, diameter and height of various native plant species under different flow conditions;

Flume Setup for Roughness Study H Depth Control Weir x =49' 31' x =60' V 2’ Flume tail tank x =0' x =66' Pumps x =17' 17' 32' 6’ 80' 9' Head Tank

Bare Soil Sample Layout 4 ft bin Width Flume width 5 ft 8 ft 6 ft 2 ft Flume Body Cross-section Partial Plan View 8 bins with a total distance of 32 ft bin length 4 ft 4 ft

STREAMBED BARE SOIL SAMPLE PREPARATION

Measurement Instrument 1) SonTek ADV 3-D Velocimeter Velocity profiles at various locations 2) Point Gages with Stilling Tube Hydraulic head 3) Ultrasound Flow Meter: Total Discharge 4) Digital Floater Water surface wave

Hydraulic Measurements For each individual experimental setup for a plant species, three different depths (three different hydraulic radii) are taken, where depths depend upon the species being studied. For each depth, three different cross-sectional average velocities are considered (within the range of 0.5 – 5 ft/second). Therefore, for each experimental setup, nine different depth – velocity combinations are considered. Each experimental setup for a particular plant species is repeated three times, with new plant patches each time, to obtain three independent replicates.

Velocity measurement locations in a cross-section 4 ft bin Width Flume width 5 ft 8 ft 6 ft 2 ft 4 ft bin Width Flume width 5 ft 8 ft 6 ft 2 ft Water depth higher than 2 ft Water depth lower than 2 ft

The velocity head profile is determined from the cross-sectionally-averaged velocity measurements at three specified locations in the plant patch section. Hydraulic radius is directly measured (depth and width of flow) through the plant patch section. The friction slope is determined from the measured total energy head (hydraulic head plus velocity head) gradient under each average depth – average velocity combination. The hydraulic head gradient is determined from measuring three cross- sectionally-averaged water depths (water surface elevations) along the longitudinal direction of the flume within the plant patch section. A Manning’s roughness coefficient that corresponds to the specified plant species and specified average hydraulic radius – average velocity condition is calculated.

PRELIMINARY EXPERIMENTAL RESULTS BASED UPON FIRST BARE SOIL REPLICATE WHILE STANDARDIZING THE EXPERIMENTAL PROCEDURES

Measured Water Surface and Energy Gradient Lines