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SELECTION OF STUDY SITES

Jay O’Keeffe,

UNESCO-IHE Institute for Water Education

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Study Sites

• BBM sites are the focus for (almost) all data collection activities

• An EFR is set for each site (one per section), therefore:– Each site should provide greatest range of possible

environmental conditions– These conditions are represented in a manner

acceptable to all involved specialists– Staff involved in site selection should have

experience in BBM site selection

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Data Sets

• Usually more than one site is selected– Tributaries may introduce different channel, bank or

habitat conditions affecting ecology– The EMC may differ for different river stretches– Natural transition of plant and animal communities

along river

• Number of sites is a trade-off between better representation () and a more lengthy, more complicated and more expensive process ()

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Minimum and ideal data sets

• Minimum data set depends on size and complexity of study area,

• additional considerations are:– Most specialists can spare some 4 days in workshop– One group of specialists can address 4 sites– Four sites, if chosen well, can represent 100-200 km– Required no. of sites depends on diversity of system– Always one site per river section!

• Ideal data set: two sites for each river section

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Sequence of activities

1. Aerial study to aid site selection

2. Identification of potential sites using video

3. Groundtruthing: final site selection

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Key criteria for site selection

1. Easy access

2. High diversity of physical habitats

3. Flow-senstitive & critical habitat for important species

4. Suitable for accurate hydraulic modeling

5. Close proximity to gauging weir

6. Potential to provide useful EFR information (location relative to WRD)

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Key criteria for site selection (cont.)

7. Positioned upstream of major tributary

8. Good ecological condition (to enable flow-related clues to aid understanding of flow effects on eco-system

9. Close proximity to rural communities that use river resources for sustenance

10. Potential as future monitoring site

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Key criteria for site selection (cont.)

• Sites should be selected to be representative of a river section, but

• it is more important that sites should be at a critical point in the section and exhibit flow dependent features

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Characteristics of unsuitable sites

1. Located on a bend

2. Located in relatively featureless sandy stretch

3. Consists mainly of large pool

4. Locate in inaccessible gorge

5. Impossibility to model hydraulics, in spite of excellent habitat diversity

6. Several team member consider site unsuitable

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Placement of river cross-sections

1. Locations of cross sections represent the site2. Required information

– Channel dimensions– Other data, including, but not limited to

Boundaries of vegetation zones Substratum and other details on physical habitat Vegetation

3. Coding:1. Each site has code number (most upstream: BBM site 1)2. Cross section designated with letters (most upstream: A)

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Other Fieldwork

• During site visit, some data can be collected

• Cross-section dimensions and details

• Fixed-point photography

• Hydraulics

• Fluvial geomorphology

• Riparian vegetation

• River health and aquatic invertebrates

• Fish survey

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Surveying cross sections

• Objective is to determine:

• Stage-discharge relationship

• Position of vertical vegetation zones up the banks

• Position of key plant species in these zones

• Position of key geomorphological features (to establish the flows that inundate them)

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Site selection report

• Report forms part of workshop starter document

• Contents– Purpose of the sites– Selection of the sites

• Study area, selection of river stretches, helicopter flight, use of aerial video, field visit: final selection of sites

– Characteristics, advantages and disadvantages of each site

– Final site selection

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Fig 7.1 BMM sites located in river sections

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