The information below provides answers to Frequently Asked Questions raised by MoRPh citizen science surveyors, compiled by MoRPh trainers.
The MoRPh FAQs is not currently organised in any particular order, but best searched for relevant information to specific queries.
If your question is not addressed below, we would welcome an email via email@example.com and we will be happy to advise and add your query to the FAQs library.
What are the differences between chutes and cascades?
Chute flow is a particular flow type that describes the fast movement of water over a steep river bed, typically formed by boulders, where the flow ‘hugs’ the rock surface compared to a free fall where water is separated by an air gap from the underlying river bed.
NB – the different flow types in MoRPh are arranged along an energy gradient, with chute flow fitting between higher energy free fall and lower energy broken standing wave flow types.
A cascade is a physical feature where water travels rapidly down a steep channel in threads separated by boulders and is comprised of a mixture of mainly free fall, chute and broken standing wave flow types.
Images provided in the MoRPh guidance illustrates chute flow type (A) within a cascade feature (B).
How is a marginal backwater defined and why is this in the bank face section rather than the channel bed?
A marginal backwater is a sheltered area at the edge of the channel, where the water is slower flowing (has a lower energy flow type) than in the main part of the flow. During low flow conditions, the flow type would usually be ‘no perceptible flow’. Marginal backwaters are formed either within an irregularity in the line of the bankface providing a sheltered alcove, or downstream of a feature within the channel, e.g. outcropping rock, boulders or large wood, which has deflected the main flow to create a sheltered area behind it.
The ‘marginal backwater‘ feature is included on Sheet 3 which records data for Bank Face and Channel Margins, along with marginal bars and marginal vegetation. All of these features are located along the margin between the bank face and water’s edge.
Are nettles/bracken recorded as tall herbs and grasses or scrub? and what if they are short early in the year but will grow tall?
Terrestrial and aquatic vegetation are recorded as morphotypes. Terrestrial vegetation are recorded in relation to canopy layers or storeys. A key difference between ‘tall vegetation’ and ‘scrub’ is not only their height but also whether they are ‘herbaceous’ or ‘woody’ types. Therefore, nettles and bracken would only be recorded as ‘tall herbs and grasses’ if they are fully grown. If they are being recorded early in the year before full development, young plants should be recorded as ‘short or creeping herbs or grasses’. In this way MoRPh survey data capture the physical variations in vegetation morphology and their abundance during different seasons.
How is a bank top defined, especially when composite, two-stage or with a set-back embankment?
The boundary of the bank face and bank top should be defined at the start of each MoRPh survey. The bank top begins by definition, at the top of the bank face (steeper part of the cross profile at either side of the water surface and low channel edge features), where the angle of slope from the steeper bank faces changes to a more level profile (i.e. the outer flatter area across which water would spread onto the valley bottom or flood plain during high river flows).
Where there is a ‘natural’ composite bank face profile, there may be several irregular ‘steps’ forming the bank face. For example, some river banks develop cracks and then pieces slide downwards to form an irregular profile. In this case, the bank top is best assessed in relation to the opposite bank level. For example, if there is a flat area that is large enough (e.g. > 2m wide) to be part of a mini-floodplain and/or is level with the top of the opposite bank, it should be classed as bank top.
Where there is an ‘artificial’ two-stage or set back embankment bank face profile, the bank profile should be recorded as two-stage or set back embankment when any part of the second stage or embankment is within 10m of the top of the lower stage. When defining the bank face and top for survey, the bank face refers to the steeper sides of the lower bank or first stage, and the bank top extends from the top of that lower bank to include whatever part of the second stage or embankment falls within 10m of the defined (lower) bank top.
How are unbroken standing waves defined vs. ripples?
Different flow types are associated with different levels of flow energy and so vary with flow velocity and water depth. The MoRPh survey list of flow types is arranged along this energy gradient, with unbroken standing waves fitting between higher energy broken standing waves (with white frothy crests) and lower energy ripple flow types.
Unbroken standing waves are characteristically associated with coarser sediments, shallower and lower flow velocities than ripples. Their stronger connection with coarser substrates and shallower water means that unbroken standing waves ‘stand’ and bob up and down at a particular point in the channel usually where a coarse stone (cobble) or other obstruction is located on the bed.
In contrast, ripples move downstream. They are not associated with the sediment particles on the bed but are simply a distortion of the water surface as the water moves downstream. Ripples should not be recorded if they are created by wind on the water surface. Wind-ripples are often detected if the ripples are not moving in a downstream direction with the flow.
In areas of smooth flow, the water is usually deeper and/or flowing more slowly that where there are ripples and so the water surface remains smooth and does not distort to form ripples.
How are braided or anabranching / anastomosing rivers defined vs side channels?
This question comes up a lot in discussions, especially in relation to wet woodland or wetland restoration schemes. Each site will be unique and the key to defining survey subreaches (for a MoRPh10 survey) very much depends upon what baseline or changes you are hoping to capture in the data, the accessibility and the scale of the river being surveyed. The overarching aim should be to make surveys replicable so that future surveys can be compared. Interpretation of the raw data (or indices) will depend upon the context of the site and what aspects of the data (e,g, changes due to events or interventions) are being investigated.
MoRPh is designed to survey a single thread river channel. This could be a braided channel (containing numerous mid-channel bars), which is technically multi-thread, if all elements of it are sufficiently visible to be recorded accurately. It could also be a channel divided by one or more islands, again technically a multithread channel (this time anabranching), if all elements of it are sufficiently visible to be recorded accurately. However, truly braided and anabranching channels are usually wide and contain obstructions which prevent accurate and comprehensive recording. Under these circumstances, MoRPh should be used to record the characteristics of a selected single thread with detailed notes to enable replication for the chosen channel. If a comprehensive survey is needed, MoRPh can be applied to several individual threads, ensuring that at least the main thread(s) are surveyed.
There are very few truly multi-thread (braided or anabranching / anastomosing) rivers in the UK. However, it is quite common for rivers to contain large islands that block the view of the opposite bank. In this case, it is appropriate to survey from the bank to the side of the island(s) that is visible but make sure that you note that you have surveyed, for example, the left bank channel across to the island, in the notes on the survey.
In other cases, it may be appropriate to include an island or islands within the surveyed module, if there is confidence in being able to record all of the details of the channel accurately from the survey location. Furthermore, you may have to survey some modules of a river to central islands whereas other, adjacent, modules may be fully visible and so completely surveyed. In these cases, make sure your notes explain the extent of the channel you have surveyed in each case.
If you are interested in discussing how MoRPh can best assess a complex system you are working on please drop us a line via firstname.lastname@example.org and we will be happy to advise.
What is an island?
Islands are formed by different processes. In some river systems, islands form when the river flows across its floodplain during a major flood and cuts a new channel, leaving a piece of its floodplain surrounded by water. In these circumstances, the island surface with its terrestrial vegetation would typically be at the same level as the bank top and adjacent floodplain area.
In other systems, islands may evolve over time as mid-channel bars become vegetated, trap fine sediment and build upwards until the successional vegetation becomes more dominated by terrestrial species as the feature becomes less frequently inundated.
In either case, an island has a flatter top and steeper sides than a vegetated bar and its relatively flat surface supports terrestrial vegetation and is at or close to the level of the surrounding bank tops.
…and how should an island be recorded, if you can’t see the end of it but can see the channel split?
If a single module contains an island feature, this should be recorded as such. Where a module includes only part of an island, then the primary channel should be identified with the secondary channel recorded as a side channel with additional comments recording this decision in the notes section. Always make a note, take photos and if possible a sketch to record any anomalies so that future surveys capture comparable data. (See also comments on ‘Anabranching / Anastomosing Channels’ above)
Every unique river system will have some elements within it that do not ‘fit’ the MoRPh standardised recording system. The priority for the MoRPh surveyor should be replicability i.e. the ability for other surveyors to replicate the approach of a previous survey.
What is a berm? & what is a bench?
Marginal bars, berms and benches represent evolving or successional features that are created and ‘built’ by river processes at the channel edges as sediments are deposited over time. By definition, marginal bars are depositional features made up of the same sediment type(s) as the channel bed with a rounded cross-profile and sloping edge angled towards the channel. As marginal bars develop, and where conditions allow them to become covered in vegetation, more sediment will be captured between the plants. As the water between the plants becomes calmer, allowing particles to settle, fine sediments will become increasingly dominant.
As vegetated marginal bars grow, they narrow the channel and their form changes as they interact with the river flow. Eventually, as the vegetated bar enlarges, the flow begins to erode its outer edge, creating the characteristic ‘square edge’ of a berm with a distinct break of slope between the flatter top and steeper edges. The flatter top of the berm usually corresponds roughly to the typical low flow water level in the river and tends to be covered with wetland rather than aquatic plant species.
Over time, increasing deposition on the top of the berm, increases the elevation and smoothness of its top, until its height is clearly above low flow level, when it is described as a bench. Because of its increased height, it is inundated less and less frequently and so more terrestrial species become established.
Eventually the elevation of the top of the bench may match that of the bank top, and the bench develops into an extension of the bank.
When we refer to aquatic vegetation do we just mean aquatic species?
In MoRPh surveys, all vegetation is recorded according to its form (a morphotype) rather than by species, with the exception of problematic/invasive non native plant species (see note below).
For aquatic vegetation, the survey records plants growing in, on or close to the edge of the water, with the morphotypes including emergent broad leaved, emergent linear leaved, submerged broad leaved, submerged linear leaved, or submerged fine leaved.
All floating or submerged vegetation morphotypes will be aquatic species tolerant of immersion in water.
At the channel margin, a mix of aquatic and semi-aquatic (wetland) emergent vegetation species may be observed, although generally where inundation is continual or frequent, aquatic species will dominate. If vegetation is growing directly at the water’s edge, emerging from the water where it will have an effect on flow, this will be recorded as ‘aquatic vegetation’.
Are problem invasive plant species included in the abundance records for aquatic vegetation ?
Problematic or invasive non-native aquatic plants are included within the aquatic vegetation abundance records as morphotypes but their abundance is also recorded separately by species type.
Why does MoRPh record adverse conditions?
MoRPh surveys should be conducted during relatively low flow. They should not take place under unsafe conditions which may also obscure channel features e.g. elevated flows (although sometimes this is unavoidable, safety should never be compromised!). It is important for surveyors to note when bed visibility is impaired, for example, due to water depth or turbidity (i.e. cloudy) water.
When bed visibility is impaired, this should be recorded as an adverse condition including how much of the whole bed is visible and why e.g. only 10% of the bed visible due to deep and/or turbid water. This is important as it will affect the level of accuracy of the bed substrate data for that survey and comparisons with survey data collected on other occasions.
(MoRPh surveyors with a good knowledge of fluvial geomorphology may be able to record the bed material based on other observed characteristics, but without such in-depth knowledge, the ‘Record what you see and not what you know’ rule should always be applied to determine the extent of visible bed substrate and this should be recorded alongside of the extent of non-visible channel bed.)
How accurate do channel water depth & bank heights need to be?
The channel dimensions are not included within the calculation of the MoRPh indices. They are designed to indicate the scale and broad form of the channel, and in many cases may indicate whether the channel is modified. While precise values are not essential, it is a good idea to improve the accuracy of visual estimates, by practising and calibrating estimations of water depth, heights and distances at safe locations during dry weather flows with a ranging pole or tape measure.
Furthermore, if you are using MoRPh for monitoring, taking accurate accurate measurements will help to identify whether the channel is changing size or shape between surveys. We do not encourage surveyors to enter the channel to take accurate measurements, but if you are intending entering the channel to conduct other surveys (e.g. Riverfly), then it is useful to measure and thus monitor channel dimensions accurately.
Note that secondary sources, such as Google Earth can help with checking MoRPh and water widths.
How can I record land use within the floodplain beyond 10m?
Land use beyond 10m is often difficult to measure in the field and so is not a component of the MoRPh field survey. However, based on analysis of secondary sources (e.g. aerial imagery and/or remotely sensed data), broader land cover and floodplain characteristics are likely to be a feature of the MoRPh floodplain survey, currently in development.
When should I record an eroding cliff on the bank face?
Wherever the bank face is approximately vertical and has less than 50% vegetation cover for at least 0.5m of the bank height. This is regardless of whether this is caused by a bank face slip or slump or by the action of river, it should be recorded as an ‘eroding cliff’.
How do I record channel substrate if the bed is not visible?
When visibility is low, the extent of bed substrate should reflect the proportion of overall bed area, not the proportion of what is visible. The degree to which the bed is not visible should be recorded under Adverse Conditions.
Should I record clay as bedrock?
We reserve ‘bedrock’ to record hard rocks. For example ‘sandstone’ would be recorded as bedrock, whereas ‘sand’ is loose material where the individual particles are not bound together. ‘Clay’ is a sticky material which may or may not be bedrock, but in either case is difficult to erode. Individual clay-sized particles rarely settle out in rivers in a coherent area of the bed, although they may settle in extremely sheltered areas. Any coherent very fine grained deposit is likely to be silt (and will not be sticky) rather than clay. Therefore, we recommend that the term ‘clay’ is used to record only observations of cohesive clay material (and not deposited fine particles) regardless of whether it appears to be a bedrock exposure or not.
What checks should MoRPh data QA include?
Area abundance for Bank Top, Bank Face, Channel Bed
Abundance or extent records need to cover the whole area being observed. For example, if 2 x P are selected (2 x <33%), then the full area is not accounted for. At least one value needs to be extensive. NB – Bank top artificial cover – records the proportion(s) of different artificial cover for the whole survey area (i.e. module length x 10m back). Water surface area / flow type - records the flow habitats covering the whole water surface area within the module. If highest extent is (P) then at least 3 types must have that value.
Linear abundance for Channel Margin
The extent of marginal / fringing vegetation is linear (not relating to the whole bank face area).
Photographic sense checks
We strongly recommend that 3 of the maximum 4 photographs should be taken to characterise the entire module by taking (1) a photograph looking straight across the channel at/near the module mid-point, (2) a photograph from/near the midpoint looking at the downstream part of the module, (3) a photograph from/near the midpoint looking at the upstream part of the module. This leaves a final photograph that can be used to monitor a particular feature or to support a particular query.
Photos (1) to (3) should be examined carefully to make sure that recorded features match what is in the survey images. Although not every feature will be visible, the general characteristics of the channel can be used to check many elements and also to monitor changes between surveys.