against a flat plate. In this way, an instantaneous point 

 sample of suspended sediment can be collected. The objec- 

 tive in designing such a sampler is to minimize flow 

 disturbance prior to sampling. However, the degree to 

 which such a sampler disturbs the flow does not appear to 

 have been investigated, and the sampler is not recommended 

 for use near the river bed. An example of an instantaneous 

 capture vertical sampler is the Eakin sampler shown in 

 Figure A2 . The sampler consists of a cylinder that is held 

 above a lower disk prior to sampling by a catch mechanism. 

 A messenger weight, released from above, triggers the 

 cylinder which falls onto the base plate, thereby collect- 

 ing the sample. A more streamlined version of this sampler 

 with multiple sampling capability is shown in Figure A3. A 

 similar multiple instantaneous vertical sampler that has 

 recently been used to measure suspended sediment transport 

 in the nearshore coastal zone is the Kana sampler (Kana 

 1976). This sampler is discussed in detail in the section 

 entitled "Coastal Suspended Sediment Samplers." 



(3) Instantaneous Capture Horizontal Sampler 

 Instantaneous capture horizontal samplers consist of 

 horizontal cylinders with flaps on each end that can be 

 closed when the sampler reaches the desired sampling point. 

 Water and sediment flow through the cylinder as it is being 

 lowered to a particular depth. Advantages of this type of 

 sampler include its simple design and mechanism, the 

 capability to sample close to the river bed, and the 

 capability to use the sampler in varying depth streams. 

 Multiple samples through the depth must be collected to 

 measure a representative average suspended sediment con- 

 centration. The degree to which the sampler disturbs the 

 flow has not been investigated, but is believed to be 

 minimal. An example of an instantaneous horizontal sampler 

 is the Leitz sampler, shown in Figure A4, consisting of a 

 brass cylinder 1 ft (30.5 cm) in length and 3 in. (7.6 cm) 

 in diameter with disk doors that swing shut when released. 



(4) Bottle Sampler 



Bottle samplers are the simplest of suspended sediment 

 samplers and consist of a standard container such as a milk 

 bottle or fruit jar. This type of sampler is lowered to a 

 sampling point, and the water -sediment mixture fills the 

 container displacing the air. Advantages of these samplers 

 are that they are simple in design and easily facilitate 

 the transport of individual samples to the laboratory. 

 Disadvantages of bottle samplers outweigh the advantages 

 and include: excessive disturbance to the flow, inter- 



A6 



