Description
A bedload trap is a portable sampler designed specifically for collecting gravel and cobble bedload (4 to 180 mm in diameter) in wadeable streams. Bedload traps consist of an aluminum frame with a 12 by 8 inch (0.3 by 0.2 m) opening to which a 3- to 5.5-ft (0.9 to 1.65 m) long trailing net is attached. Bedload traps are installed on ground plates that are anchored to the stream bottom with metal stakes. Traps do not have to be hand-held while sampling and have a large volumetric capacity. This permits collection of bedload over relatively long intervals, typically one hour per sample. In this document, we provide detailed guidelines for bedload trap construction and operation. We describe component parts and offer instructions for making the nets and assembling the sampler. Appropriate site selection and preparation are discussed as well as bedload trap installation, use, and maintenance. These guidelines also show how to process the collected bedload samples in the field and how to perform some of the typical calculations used in bedload evaluation.
