Overview
ISO 4364:1997 - Measurement of liquid flow in open channels - Bed material sampling - provides internationally accepted guidance on methods to obtain and handle bed-material samples from open channels. The standard covers sampling of both non-cohesive and cohesive sediments (including material containing some fine gravel) principally to determine the grain-size frequency distribution needed for bed-material load computations and flow estimation.
Key topics and technical requirements
- Scope and definitions: Clarifies terms (e.g., sand defined as 0.0625–2 mm) and distinguishes bed-material samplers from bed-load discharge samplers. The standard differentiates cohesive vs non-cohesive material based on the presence of a fine fraction.
- Sampling strategy: Recommends sampling at various flow stages and locating sampling sites close to hydraulic measurement stations (straight, uniform channel sections preferred). For transport studies, sampling at each vertical across the cross-section is advised.
- Sampler selection and sample integrity: Emphasises choosing samplers and methods appropriate to site conditions; explains types of sample disturbance - loss of fines (“disturbed”) and loss of fabric (“structural disturbance”) - and their implications for non-cohesive vs cohesive sediments.
- Sampler types described:
- Hand-held samplers: sampling cylinders, pipe scoops, bag scoops, push/hammer corers, freeze-core samplers (freeze-cores produce spindle-shaped frozen cores up to ~0.5 m).
- Lightweight remotely-operated samplers: pole-mounted scoops, drag buckets (dredges), grab samplers with 90° or 180° closure (top ~0.05 m sampled).
- Heavier remotely-operated samplers requiring handling machinery: anchor dredges, large grabs, corers (e.g., free-fall gravity corers).
- Performance limits and practical notes: Depth and velocity limitations are given for various samplers (e.g., lightweight scoops generally for depths <4 m and velocities <1.0 m/s; freeze-cores not suitable for scuba or depths >3.5 m). Typical sample depths and masses are provided for each method.
Applications and users
ISO 4364 is used to support:
- Sediment transport analysis and bed-load computations
- River, canal and reservoir sediment investigations
- Hydraulic resistance and flow estimation studies
- Environmental monitoring, dredging operations and civil engineering design
Typical users: hydrologists, sedimentologists, river engineers, environmental consultants, dredging contractors and organizations performing hydrometric determinations.
Related standards
Relevant ISO references cited in the standard include:
- ISO 712 (vocabulary and symbols)
- ISO 4363 (suspended sediment measurement)
- ISO 4365 (concentration and particle-size measurement)
- ISO 9195 (gravel bed material sampling)
Keywords: ISO 4364, bed material sampling, open channels, sediment sampling, grain size distribution, core samplers, grab samplers, hydrometric determinations.
