Figure 8. DUCK85 sediment transport experiment, directed by Dr. Nicholas Kraus (CHL)

time to remove the instruments

sensing techniques and students to

incredible speed and complexity at

before winter weather set in. Sur-

Duck.

which sandbars evolve during a

veys by the CRAB provided frequent

storm. Because of the circulation

The DUCK82 experiment began

updates of the morphology sur-

associated with the development of

to define the format and logistics of

rounding the instruments. As the

migrating rip channels, adjacent pro-

the experiments that followed. In

experiments became larger and

file lines showed opposite trends

each, the CRAB was used to

more complex, one key to their suc-

with offshore bar migration on one,

water-jet precisely located long pipes

cess was the developing experience

and accretion on the other. Since

or pipe frames into the bottom to

being gained by the FRF and by

the cross-shore focus of DUCK82

support the instruments which were

repeating participants.

did not fully resolve this complexity,

cabled back to collecting systems on

the DUCK85 experiment was

shore. Typically the number of

planned with more frequent surveys

instruments was thought to be suffi-

Table 1. Instrument Nodes

and a larger array of instruments.

cient, based on the understanding of

During the Duck Experiments

DUCK85 differed somewhat by

the dominant processes at the time.

having a separate mild wave phase

Experiment Instrument Nodes1

As the understanding of the pro-

in September focussing on sedi-

cesses improved, the number of

ment-transport measurements

ASEX

0, instrumented sled

instrument locations or nodes and

(Figure 8), and a storm wave phase

the number of instruments at each

DUCK82

7, instrumented sled

in October that provided some of the

node increased (Table 1). Instru-

DUCK85

best quantitative data on the rapid

ments were deployed during the

changes that occur during storms

SUPERDUCK

30, instrumented sled

mild conditions of late summer in

(Mason et al. 1987). In fact, the

order to be ready to measure the

DELILAH

19, instrumented sled

CRAB surveys during DUCK85

changes caused by the first fall

DUCK94

41, instrumented sled

uniquely captured the initial, and

storms of September or October.

subtle, development of a rip current

SandyDuck

105, instrumented sled

Instruments in the surf zone require

through a linear sand bar (Howd and

a high level of attention and mainte-

Nodes held one or multiple instruments

Birkemeier 1987). DUCK85 and the

nance. Therefore, the experiments

experiments that followed provided

generally lasted only a few weeks to

The DUCK82 experiment was

training opportunities for Corps office

two months to obtain observations

also a landmark in revealing both

staff. During DUCK85, more than 15

under a range of conditions includ-

the importance of sandbar morphol-

District engineers and scientists

ing storms and to have sufficient

ogy to nearshore dynamics and the

Figure 8. DUCK85 sediment transport experiment, directed by Dr. Nicholas Kraus (CHL). The researchers are tending

sediment traps facing into the longshore current which is being measured by the two current meters located to their right.

Further to the right, the line of "photopoles" was observed by movie cameras to measure wave conditions