Appendix 12. Hydromorphology – Geomorphological Surveys

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Scientific best practice

  • Consult a fluvial geomorphologist to identify the likely change in processes and physical forms following restoration for your river type.
  • Consult with a fluvial geomorphologist to select methods that will best record changes in physical forms.
  • Use habitat survey methods and species survey methods (macroinvertebrates, fish) to link geomorphological changes to biological and ecological changes.
  • Use the BACI approach (before-after-control-impact) with both positive and negative controls.
  • Sample before, after and controls in the same one month window and with similar flow regime conditions.

1. Introduction

Hydromorphology is a discipline which is now recognised as integral to river and catchment management. It can be defined as:

‘the physical habitat constituted by the flow regime (hydrology and hydraulics) and the physical template (fluvial geomorphology)’ (Orr et al., 2008).

The term hydromorphology was first mentioned in EU Water Framework Directive (WFD; European Commission 2000) which required hydromorphology to be considered as a ‘supporting’ element in the assessment of water bodies. It is now often thought that hydromorphology should be a key part in the identification and delineation of water bodies and that it should be assessed on its own as an integral part of the WFD assessment (Ecostat 2019 Resource document on Hydromorphology in the WFD).

Hydromorphology (the study of habitats) combines three sciences: hydrology (the study of the movement of water), geomorphology (the study of sediment processes) and ecology (the study of ecosystems).

HYDRO MORPHO LOGY
Hydrology Geomorphology Logia
the study of the movement, distribution, and quality of water on Earth the study of the process of sediment transfer (i.e. erosion, transport and deposition) in rivers, and of the channel forms produced by these processes the study of’ or ‘subject matter’ in ancient Greek

Since the late 20th Century, scientists and practitioners have been developing survey and assessment methods to inform the management of rivers. Early methods, such as River Habitat Survey (Raven et al, 1997) and River Corridor Survey (NRA, 1992) focused on recording or mapping the physical habitat represented by geomorphological forms and functional habitats structures such as leafy debris and tree roots. In the UK, national River Habitat Surveys were carried out in 1994-1996 and 2007-2008 on a randomly selected sample of sites to provide an inventory of habitat features and modifications across the river network. Every 10km2 was surveyed three times in England and Wales, thus providing a geographically representative picture of habitat diversity and quality (Raven et al, 1997). Although River Habitat Surveys record the presence of erosion and deposition features, they do not provide an assessment of the river processes that create them over time or the historical context in which they occurred.

Methods for the assessment of geomorphological processes over space and time were developed to provide further insights in the causal chains that lead to the development of river ecosystems. The Fluvial Audit methodology (Sear et. al., 1995) is aimed at establishing sediment budget, identifying temporal channel adjustment and potential pressures and impacts on geomorphological processes. Fluvial audits aim to develop an understanding of processes (i.e. erosion, transport and deposition of sediment) that drive the distribution of forms (e.g. gravel bars) that shape habitats for species. Fluvial audits involves the investigation of old maps and photographic evidence, as well as the identification of relic features that provide insights in the history of the river floodplain system and the factors that have been affecting them. Fluvial audits provide a qualitative view on river system development over space and time that is complementary of river inventories that are aimed at assessing current habitat condition and diversity.

RIver Habitat Surveys and fluvial audits methods require a fair amount of expertise and training to be carried out. Recently, methods aimed 'citizen scientists' were developed to provide a wider spectrum of application and raise the awareness of the public on hydromorphological issues. The Modular River Survey (MoRPh) and the citizen RIver Habitat Survey (cRHS) are methodologies derived from the RHS that can be used by less experienced surveyors and members of the public. MoRPh was also developed into a survey for expert users, and applied to the calculation of the Biodiversity Net Gain metrics in the UK. Both methodologies are linked to online databases and provide assessments of pressure and habitat quality using different approaches and metrics. The both feature online maps, databases, calculation algorithms and structured training courses.

2. Survey comparison

There are several surveys that have been developed to collect data on river and floodplain forms, processes, features, and habitats. The complexity and variety of fluvial systems means that no survey can record everything, and methods naturally have to focus on certain elements. For example, some methods like the Fluvial Audit focus on sediment budgets and river processes, whilst methods like the River Habitat Survey (RHS) and Modular River Survey (MoRPh) primarily record habitat features and pressures. It is therefore crucial to select the right survey method for the purpose of your project and the outputs required.

Method First published Type Primary focus Typical length (m) Typical time (hrs) Citizen Science
Cross Sections N/A Measurement Morphological forms 100 2 No
Fluvial Audit 1995 Form Sediment budgets 10,000 15 No
Geo-River Habitat Survey (GeoRHS) 2003 Form Channel, floodplain habitats and sediment 500 3.5 No
Geomorphological Dynamics Assessment Form Site-scale fluvial processes 300 7.5 No
Geomorphological mapping Map Morphological pressures 3,000 2 No
Modular River Survey (MoRPh) 2017 Form Detailed river habitat inventory and condition assessment 20 0.3 Yes
Modular River Survey (River Condition Assessment) 2020 Form Detailed river habitat inventory and condition assessment 100 1.7 No
Morphological Impact Assessment System (MImAS) 2012 Map & tool Morphological pressures 500 2 No
River Habitat Survey (RHS) 1994 Form Baseline river habitat quality assessment 500 1.5 No
Citizen River Habitat Survey (cRHS) 2022 Form Baseline river habitat quality 500 1.5 Yes
River Hydromorphology Assessment Technique (RHAT) 2013 Form River habitat condition assessment 500 1.5 No
Sediment sampling 1954 Measurement Sediment size distribution 100 7.5 No
Topographic Survey Measurement Morphological forms 500 7.5 No
Urban River Survey 2001 Form River habitat inventory and quality assessment in urban environments 500 1.5 No

2. Fluvial Audit

Fluvial Audit Method Manual (Environment Agency, 2005, p4).

The Fluvial Audit (FA) uses contemporary and historical field surveys, maps, and documentary information to gain a comprehensive understanding of the river system and its catchment. The river is divided into a series of reaches defined by natural changes in the geomorphological controls of the river system. In addition, within each reach, information on channel dimension, bank properties, flow types, anthropogenic controls and catchment influences, the specific location, type and severity of bank erosion processes, bank protection works and inchannel modifications are mapped.
Find out more about Fluvial Audit

3. Geomorphological Dynamics Assessment

GDA is a detailed assessment of geomorphological processes at the reach scale. The surveyor assesses geomorphological forms and sediment dynamics to gain an understanding of process-form interactions (Sear et al., 2004). The specific methods are tailored to the unique characteristics of each site by an expert geomorphologist, so as to ensure that the data collected is relevant to the issues at hand. Research-level methods are often applied from best-practice scientific studies to provide a comprehensive report on the geomorphological dynamics of a site.
Find out more about Geomorphological Dynamics Asessment

4. Geomorphological mapping

Geomorphological mapping is an important technique for the documentation and reconstruction of landscapes. In recent years it has evolved from a purely field-based exercise, to one that is heavily technologically reliant. Geographical Information Systems (GIS) have allowed developments in geomorphological mapping to progress, enabling more high-resolution mapping and visualisation of landscapes. This is useful to highlight features and issues, prioritise works and monitor adaptation of environments to restorative actions.
Find out more about Geomorphological mapping

5. Habitat Mapping (biotope)

Biotopes, functional or mesohabitat assessment is a technique used to map a watercourse, stillwater or wetland by breaking it down into components. Biotopes are defined as an area with uniform environmental conditions that provide a habitat for a specific assemblage of plants and animals. Functional habitats (see Harper and Smith, 1995 and Kemp et al, 1999) are areas where hydrological and physical processed for distinct habitats which support distinct invertebrate assemblages. Functional habitats in rivers are called 'mesohabitats' by other researchers e.g. Pardo and Armitage, 1997. Some workers map the physical biotopes rather than the functional habitats that they provide. Biotopes or functional habitats may be mapped directly or highlighted on other maps produced as part of a study such as a River Corridor Survey.
Find out more about Habitat Mapping

6. Modular River Survey

MoRPh logo.png

The Modular River Survey is a suite of tools for assessing rivers, many of which have been developed in partnership with Queen Mary University of London and the Environment Agency. The MoRPh survey is one of these tools. It records the physical structure of a river and its margins at a scale that complements biological surveys, enabling linkages between organisms and physical habitats to be explored.

MoRPh

The MoRPh survey was developed for citizen scientists to capture physical habitat information at an appropriate scale to complement biological monitoring. The survey records the detailed physical structure of three areas of the river environment: the river bed, bank faces and bank tops, over a channel length of 10 to 40 m, depending upon the channel width. The survey records the presence and abundance of sediments, physical habitats and landforms, vegetation structure and human modifications and pressures across these three areas of the river environment. Surveyors upload data into an open, shared workspace within the Modular River Survey Information System. The Information System supports data management, querying and downloads and also extracts and maps indices from the surveys relating to habitat character and complexity and human interventions and pressures. Data are shared more widely via the Catchment Based Approach (CaBA) data hub to support Catchment Partnership and monitoring linked to Catchment Action Plans. If surveyors undertake a MoRPh10 survey, by recording ten end-to-end MoRPh surveys, additional summary indicators are computed and mapped for the entire 100 to 400 m surveyed river length.
Find out more about MoRPh

River Condition Assessment (RCA)

The River Condition Assessment combines the original MoRPh survey with a desk-based estimation of the hydromorphological River Type to interpret a more detailed set of indicators for professional river condition assessments. Five MoRPh surveys are combined to create a MoRPh5 survey of a 50 to 200 m reach (250 m for canals, navigable rivers, and large rivers). The Modular River Survey Information System computes 32 river condition indicators for each MoRPh5 survey. The values of these indicators are combined to assign the surveyed river length to one of five Condition classes, according to the river’s hydromorphological River Type. Unlike MoRPh, the RCA is accessed through a private workspace. The tools on this workspace allow environmental professionals to undertake baseline assessments, scenario modelling, Biodiversity Net Gain reporting and detailed post-project appraisal.
Find out more about RCA

7. Morphological Impact Assessment System (MImAS)

MImAS is an assessment system developed by Greig et al. (2006) which is based around the assumption that rivers have the capacity to resist and absorb a certain level of morphological pressures, and that this can be quantified and assessed. Beyond a defined threshold, the hydromorphological condition and ensuing ecological status of the river is at risk of being degraded. It is used by the Scottish Environment Protection Agency (SEPA) to assess activities (i.e. management actions or structures such as dredging or embankments) that could impact the morphological and ecological condition of rivers. The assessment involves the collection of pressure data and river type information which is then used to quantify the level of morphological impact.
Find out more about MImAS

8. Pressure flyover survey

The aim of this desk-based survey is to identify and record the presence, absence and extent of hydromorphological pressures on rivers. Google Earth is used alongside Google Street View and existing pressure datasets to collect data on pressures over large distances where extensive on-site pressure surveys are not possible.
Find out more about Flyover survey

9. Repeat Cross Sections

Cross section surveys carried out before the restoration work can be compared with surveys taken in exactly the same place, but which are repeated at predefined intervals (for example immediately post restoration, then 1 year after and three years after). The repeat cross sections will then show how much the channel has changed as a result of the restoration work.
Click here for more information on Repeat Cross Sections

10. River Habitat Survey

Figure 1: RHS form

River Habitat Survey (RHS)

River Habitat Survey (RHS) is a method developed in the UK to characterise and assess, in broad simple terms, the physical character of freshwater streams and small rivers. It is carried out along a 500m length of river. Observations on channel features and modifications are made at 10 equally spaced spot-checks, together with an overall “sweep-up” summary for the whole site. Other information such as valley form and land-use in the river corridor is also collected.
Click here for more information on RHS

Citizen River Habitat Survey (cRHS)

River Habitat Survey (RHS) is a method developed in the UK to characterise and assess, in broad simple terms, the physical character of freshwater streams and small rivers. It is carried out along a 500m length of river. Observations on channel features and modifications are made at 10 equally spaced spot-checks, together with an overall “sweep-up” summary for the whole site. Other information such as valley form and land-use in the river corridor is also collected.
Find out more about cRHS

Geo-River Habitat Survey (GeoRHS)

Geo-RHS is the geomorphology component bolt on to RHS. It largely targets features and dimensions that relate to the processes of sediment transport in the channel and floodplain. Geomorphology is inherent in RHS surveys but is limited in scope and does not extend to the floodplain or consider the wider catchment features. Updated field survey forms are now available. The information will be used in tandem with RHS data to develop indicators of channel and floodplain status, naturalness, and modification.
Find out more about Geo-RHS

11. River Hydromorphology Assessment Technique

The Environmental Protection Agency (EPA) in the Republic of Ireland and the Northern Ireland Environment Agency (NIEA), through the North South Shared Aquatic REsources (NS SHARE) project, have collectively developed a technique to allow for in-field assessment and classification of rivers in terms of their hydromorphology. This was utilised in the characterisation and evaluation of watercourses under the requirements of the EC Water Framework Directive (EC/60/2000), colloquially known as the WFD Directive.
Find out more about the River Hydromorphology Assessment Technique

12. Sediment sampling

Sediment sampling involves the collection of data on sediment size distribution in a channel. This data can be used to understand reach and catchment processes, as well as plan and design river restoration projects.
Find out more about Sediment sampling

13. Topographic Survey

Topographic surveys consist of the height of the ground above a datum being recorded at regular (predefined intervals) along a transect. The transect can be down the river bed (i.e. a bed level survey) or across the channel (i.e. a cross section survey). Cross section surveys can include just the channel (i.e. from bank top to bank top) or might also include the floodplain. Topographic survey can also be done in a grid pattern.
Find out more about Topographic Survey

14. Urban River Survey

The Urban River Survey (URS) is a scientific assessment method and suite of tools that supports the work of river practitioners including managers in urban environments and other heavily modified landscape settings. The survey is also available to volunteer groups who are engaged with river project officers within an urban or heavily modified landscape setting. The survey, which is a development of the River Habitat Survey, records information on the physical structure and processes of stretches of urban river, typically 500 m in length, that conform to a single engineering type.

Survey data are uploaded to an Information System that stores and maps the data, extracts a series if summary indices and supports data downloads. Indices calculated from survey data are used to assess the relative physical quality of individual surveyed stretches within the range achievable in an urban or heavily modified river environment.
Find out more about Urban River Survey

15. References

Central Fisheries Board and Compass Informatics (2005)
Hydromorphology of Rivers – a desk study to determine a methodology for the monitoring of hydromorphological conditions in Irish Rivers for the Water Framework Directive (2002-W-DS/9), 125pp.
Couper, P., Stott, T., and Maddock, I. (2002)
Insights into river bank erosion processes derived from analysis of negative erosion-pin recordings: observations from three recent UK studies. Earth Surface Processes and Landforms 27, 59-79.
Downs , P. W., and Brookes, A. (1994)
Developing a standard geomorphological approach for the appraisal of projects, in Kirkby, C. and White, W. R. (eds.), Integrated River Basin Management, John Wiley and Sons, Chichester, UK, 299-310.
Downs, P. W., and Thorne, C. R. (1996)
A geomorphological justification of river channel reconnaissance surveys, Transactions of the Institute of British Geographers, New Series 21, 455-468.
Environment Agency (2007)
Geomorphological monitoring guidelines for river restoration schemes, 73pp
EU Life-Environment Project (1999)
Wise Use of Wetlands, Task 1: Identification of techniques for appraisal of floodplain wetlands, 15pp.
Harrelson C. C., Rawlins, C. L., and Potyondy, J. P. (1994)
Stream channel reference sites: An illustrated guide to field technique. General Technical report RM-245, Fort Collins, CO: United States Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station, 61p.
Hicks, D. M., and Gomez, B. (2003)
Sediment Transport, in Kondolf, G. M., and Piegay, H. (eds.), Tools in fluvial geomorphology, John Wiley and Sons Ltd., Chichester, UK, 425-461.
Molloy, H. (2009)
Hydromorphological changes to the River Cole over a twelve year period and the changes after further restoration works: the addition of woody debris and gravel to change bed profile and create flow diversity, Thesis submitted in partial fulfilment of the requirements for the degree of Msc Water Management (Environmental option), Cranfield University, 59pp
Naden, P., Smith, B., Jarvie, H., Llewellyn, N., Matthiessen, P., Dawson, H., Scarlett, S., and Hornby, D. (2003)
Siltation in Rivers. A Review of Monitoring Techniques. Conserving Natura 2000 Rivers Monitoring Techniques Series No. 6, English Nature, Peterborough.
Skinner, K., and Thorne, C. (2005)
Review of Impact Assessment Tools and Post Project Monitoring Guidance. Report by Haycock Associates for SEPA, 65pp.
Stephens, A. (2006)
A comparative investigation into the morphological adjustment of the Sinderland and Rye Brooks following their recent restoration, Dissertation presented for the Honours degree of Bsc, School of Geography, University of Nottingham, 66pp.
Thorne, C. R., Simon, A., and Allen, R. (1996)
Geomorphological river channel reconnaissance for river analysis, engineering and management, Transactions of the Institute of British Geographers, New Series 21, 469-483.
Thorne, C. R. (1998)
Stream Reconnaissance Guidebook: Geomorphological Investigation and Analysis of River Channels, J Wiley and Sons, Chichester, UK, 127pp.