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Neil Entwistle

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University of Zagreb

Uppsala University

University of East London

University of Leicester

Gwen Robbins Schug

University of North Carolina at Greensboro

Gabriel Gutierrez-Alonso

University of Salamanca

Macquarie University

Universidade Federal do Rio Grande do Sul

Swansea University

Jesper Hoffmeyer

University of Copenhagen

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Papers by Neil Entwistle

Quantifying and Validating Rapid Floodplain Geomorphic Evolution, a Monitoring and Modelling Case Study

AGU Fall Meeting Abstracts, Dec 1, 2017

Topographic and hydraulic controls over alluviation on a bedrock template

EGU General Assembly Conference Abstracts, Apr 1, 2017

The role of bedrock in creating habitat in temperate watercourses

AGUFM, Dec 1, 2016

Confined Floodplain Dynamics on Semi-Arid Systems

AGU Fall Meeting Abstracts, Dec 1, 2017

Small unmanned aerial model accuracy for photogrammetrical fluvial bathymetric survey

Journal of Applied Remote Sensing, Feb 26, 2019

Fluvial systems offer a challenging and varied environment for topographic survey, displaying a r... more Fluvial systems offer a challenging and varied environment for topographic survey, displaying a rapidly varying morphology, vegetation assemblage and degree of submergence. Traditionally theodolite or GPS based systems have been used to capture cross-section and breakline based topographic data which has subsequently been interpolated. Advances in survey technology has resulted in an improved ability to capture larger volumes of information with infrared terrestrial and aerial LiDAR systems capturing highdensity (<0.02 m) point data across terrestrial surfaces. The rise of Structure from Motion (SfM) photogrammetry, coupled with small unmanned aerial vehicles (sUAV), has potential to record elevation data at reach scale sub decimetre density. The approach has the additional advantage over LiDAR of seeing through clear water to capture bed detail, whilst also generating ortho-rectified photographic mosaics of the survey reach. However, data accuracy has yet to be comprehensively assessed. Here we present a survey protocol for sUAV deployment and provide a reach scale comparison between a theodolite and SfM sUAV survey on the River Sprint, Kendal, the River Ehen at Egremont, England and the Afon Elwy, at Llanfair Talhaiarn, Wales. Comparative analysis between theodolite survey and SfM suggest similar accuracy and precision across terrestrial surfaces with error lowest over solid surfaces, increasing with vegetation complexity. Submerged SfM data, captured bed levels generally to within ±0.25 m with only a weak relationship recorded between error and flow depth. Significantly, associated error when linked to channel D50 highlights the ability of unmanned aerial vehicles to capture accurate fluvial data across a range of river biotopes and depths to 2.4 m.

Meltwater temperature in streams draining Alpine glaciers

Science of The Total Environment, Mar 1, 2019

Thermal conditions in river water are of importance as they influence water quality, chemical pro... more Thermal conditions in river water are of importance as they influence water quality, chemical processes, ecology, and biological conditions in rivers. In meltwater streams draining from Alpine glaciers, temperatures measured close to glacier termini show strong diurnal variation and paradoxical seasonal variation, being cool when energy availability is greatest. This thesis aims to describe temporal variations of water temperatures in five glacier-fed streams, which drain catchments of varying percentage glacierisation, in the Swiss Alps. Contrasting patterns of ablation season meltwater temperatures, and influences of basin characteristics and river channel morphology on water temperature are assessed. Relationships between solar radiation, air temperature, and water temperature were also investigated. A model was developed in order to estimate the impact of glacier recession on meltwater temperature. Observed temperatures in the Findelenbach during one ablation season were used to calibrate the model, which was subsequently validated on other years. Paucity of data in mountainous regions necessitated a model that required few measured variables to be developed. Distinctive seasonal water temperature regime was identified for larger rivers which drain relatively steep catchments, with substantial basin ice coverage. Such a regime is not replicated in streams draining smaller glaciers with lower gradients. Patterns in diurnal ranges of temperature in rivers draining large glaciers have been identified, temperature ranges reducing during days with high radiation and rising riverflows. Stream surface area was found to be the main catchment characteristic influencing temperature in glacier-fed rivers. Measured stream albedo values suggest that surface reflectivity is unlikely to be a major control on water temperature. Stream temperatures simulated by the model demonstrate high fidelity to those measured in the field. The temperature of glacier-fed streams will increase as climate warms as the distance over which heating can occur will lengthen as glaciers retreat, despite volume of flow being augmented by the deglaciation discharge dividend.

Precipitation and temperature variations affecting glacierised Himalayan headwaters and water resources in the upper Indus and Sutlej basins

AGU Fall Meeting Abstracts, Dec 1, 2013

Drone based Quantification of Channel Response to an Extreme Flood for a Piedmont Stream

AGU Fall Meeting Abstracts, Dec 1, 2019

The influence of extreme floods on the form and functioning of upland systems has concentrated on... more The influence of extreme floods on the form and functioning of upland systems has concentrated on the erosive impact of these flows. They are seen to be highly competent with coarse sediment transport rates limited by upstream supply and moderated by the 'blanketing' effect of an armour layer. This study investigates the effect of extreme events on the upland sediment cascade subjected to a recent extreme rainfall-induced flood event. The drone-based survey generated orthophotography and a DEM surface, which was compared with historic LiDAR data. This allowed erosion and deposition to be quantified and the surface micro-variation used to characterise stable and mobile sediment. The idealised model of sediment residence time increasing downstream is questioned by the findings of this study as relatively little coarse bedload sediment appears to have been transferred downstream in favour of initial local channel erosion (moderated by legacy large sediment), mid-reach palaeo-channel reactivation, sub-channel infilling and downstream deposition of the majority of mobilised sediment across berm and bar surfaces within the active inset channel margins. Channel margin erosion was largely limited to fine sediment stripping moderated by the re-exposure of post-glacial sediment. Only a weak relationship was found between local channel slope and deposition, with storage linked more to the presence of inset berm and bar areas within the inset active channel. Downstream fining of sediment is apparent as is a strong contrast between coarser active sub-channels and finer bar and berm areas.

Ten years after the flood: a case of extended geomorphic convalescence in an upland stream

AGUFM, Dec 1, 2017

Modelling spatially distributed vegetation roughness change in a bedrock channel using LiDAR; hydraulic and morphological implications

AGU Fall Meeting Abstracts, Dec 1, 2016

Reach-Scale Hydraulic Influence on Sediment Dynamics and Morphological Development in a Bedrock Influenced River

2014 AGU Fall Meeting, Dec 17, 2014

Climatic Variation And Runoff From Himalayan Mountain Basins

AGU Fall Meeting Abstracts, Dec 1, 2012

Radiometric calibration of a dual-wavelength terrestrial laser scanner using neural networks

Remote Sensing Letters, Jan 14, 2016

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 Intern... more

Using 2D Sediment Modelling to Simulate Geomorphic Change for River Restoration Initiatives

&lt;p&gt;River restoration projects have long relied on the use of modelling in both 1D a... more &lt;p&gt;River restoration projects have long relied on the use of modelling in both 1D and 2D to simulate the changes to flow hydraulics and flood extent that alterations to a river and floodplain will have caused. These methods have grown more accurate with increasing computing power and more complex software. However, despite the developments in modelling, a significant gap remains in the usage and accuracy of sediment modelling to identify arguably one of the most important metrics of river restoration: Geomorphic Change. Therefore, this paper attempts to address this by investigating the accuracy of high-resolution sediment modelling to identify geomorphic change on Blaze Beck in Cumbria, a high energy wandering river system that has recently been restored. Comparisons have been made between the impacts of a simulated flood event created using HEC-RAS 6.1 modelling software and a real-life flood event on October the 27&lt;sup&gt;th&lt;/sup&gt; 2021, to compare changes to geomorphology and identify the degree of accuracy of the 2D change modelling compared to change measured using drone-based photogrammetry. The results appear generally accurate, predicting locations of head cutting and more general low-level erosion and deposition. Bar formation, splay deposition and general bed raising are all predicted. The model is, however, very sensitive to the gradation of sediment it has been trained with and this can skew the ratio and pattern of deposition and erosion depending on the sample data used to simulate real life conditions. The model, once refined and iterated to best simulate potential change, is functional even in a high energy hydraulically diverse environment like Blaze Beck, and will have significant value in predicting the degree to which geomorphic change will occur because of restorative or other changes to a river reach.&lt;/p&gt;

Development of a Novel, Parsimonious, Model-based Approach for Representing High-resolution Gravel Facies

2D Biotope Mapping Using Combined LIDAR, Topographic Survey And Segmented 1D Flow Modelling

ABSTRACT Reach averaged habitat availability models such as PHABSIM are limited due principally t... more ABSTRACT Reach averaged habitat availability models such as PHABSIM are limited due principally to their failure to adequately map hydraulic habitat distribution at a representative scale. A lack of morphologic data, represented in the form of sparse geometric cross-sections fails to generate the necessary detail. Advances in data collection, improved spatial modelling algorithms and the advent of cross-section based segmentation routines in 1D hydraulic models provides the opportunity to revisit the issue of hydraulic habitat mapping and modelling. This paper presents a combined technique for habitat characterisation at the sub-bar scale is presented for the River Rede, Northumberland, UK. Terrestrial LIDAR data of floodplain, banks and exposed bar surfaces at an average 0.05 m spacing are combined with sparser total station survey data of submerged morphologic features. These data are interpolated to create a uniform DEM grid at 0.2 m spacing (adequate to detect the smallest variation in hydraulic habitat in this system). The data grid were then imported into the HECRAS 1D hydraulic model to generate a 2 m spaced series of cross-sections along a 220 m sinuous single thread reach exhibiting pool - riffle point-bar morphology. The hydraulic segmentation routine then generated estimates of depth averaged flow velocity, flow depth and sub unit discharge for 40 sub-divisions of the flow width for a series of flows from 0.5 m3s-1 up to bankfull flow of approximately 9 m3s-1. The resultant hydraulic data were exported in the project coordinate system and plotted to reveal the 2D pattern of hydraulic biotopes present across the range of flows modelled. The results reveal broadly realistic patterns consistent with previous empirical studies and compare well with LIDAR based biotope maps. Analysis of the temporal pattern of biotope change indicates that biotope diversity and complexity is at a maximum at lower flows and across shallower area (riffles) and that these dominate the temporal biotope pattern revealing the importance of the low flow regime in generating and maintaining habitat diversity. The combined survey and modelling technique presented here offers a viable new approach to habitat mapping and modelling providing predictive capability when assessing changes to river morphology and flow regime.

Spatial variability of glacier decline in the Indian and Nepalese Himalaya since the 1960s

Precipitation and temperature variations affecting glacierised Himalayan headwaters and water resources in the upper Indus and Sutlej basins

Biotope mapping using combined LIDAR acoustic doppler velocity profiler survey

Role of hydrology in managing consequences of a changing global environment, 2010

Real Rivers: Defining the Natural Poster

AGU Fall Meeting 2021, Dec 16, 2021

Quantifying and Validating Rapid Floodplain Geomorphic Evolution, a Monitoring and Modelling Case Study

AGU Fall Meeting Abstracts, Dec 1, 2017

Topographic and hydraulic controls over alluviation on a bedrock template

EGU General Assembly Conference Abstracts, Apr 1, 2017

The role of bedrock in creating habitat in temperate watercourses

AGUFM, Dec 1, 2016

Confined Floodplain Dynamics on Semi-Arid Systems

AGU Fall Meeting Abstracts, Dec 1, 2017

Small unmanned aerial model accuracy for photogrammetrical fluvial bathymetric survey

Journal of Applied Remote Sensing, Feb 26, 2019

Fluvial systems offer a challenging and varied environment for topographic survey, displaying a r... more Fluvial systems offer a challenging and varied environment for topographic survey, displaying a rapidly varying morphology, vegetation assemblage and degree of submergence. Traditionally theodolite or GPS based systems have been used to capture cross-section and breakline based topographic data which has subsequently been interpolated. Advances in survey technology has resulted in an improved ability to capture larger volumes of information with infrared terrestrial and aerial LiDAR systems capturing highdensity (<0.02 m) point data across terrestrial surfaces. The rise of Structure from Motion (SfM) photogrammetry, coupled with small unmanned aerial vehicles (sUAV), has potential to record elevation data at reach scale sub decimetre density. The approach has the additional advantage over LiDAR of seeing through clear water to capture bed detail, whilst also generating ortho-rectified photographic mosaics of the survey reach. However, data accuracy has yet to be comprehensively assessed. Here we present a survey protocol for sUAV deployment and provide a reach scale comparison between a theodolite and SfM sUAV survey on the River Sprint, Kendal, the River Ehen at Egremont, England and the Afon Elwy, at Llanfair Talhaiarn, Wales. Comparative analysis between theodolite survey and SfM suggest similar accuracy and precision across terrestrial surfaces with error lowest over solid surfaces, increasing with vegetation complexity. Submerged SfM data, captured bed levels generally to within ±0.25 m with only a weak relationship recorded between error and flow depth. Significantly, associated error when linked to channel D50 highlights the ability of unmanned aerial vehicles to capture accurate fluvial data across a range of river biotopes and depths to 2.4 m.

Meltwater temperature in streams draining Alpine glaciers

Science of The Total Environment, Mar 1, 2019

Thermal conditions in river water are of importance as they influence water quality, chemical pro... more Thermal conditions in river water are of importance as they influence water quality, chemical processes, ecology, and biological conditions in rivers. In meltwater streams draining from Alpine glaciers, temperatures measured close to glacier termini show strong diurnal variation and paradoxical seasonal variation, being cool when energy availability is greatest. This thesis aims to describe temporal variations of water temperatures in five glacier-fed streams, which drain catchments of varying percentage glacierisation, in the Swiss Alps. Contrasting patterns of ablation season meltwater temperatures, and influences of basin characteristics and river channel morphology on water temperature are assessed. Relationships between solar radiation, air temperature, and water temperature were also investigated. A model was developed in order to estimate the impact of glacier recession on meltwater temperature. Observed temperatures in the Findelenbach during one ablation season were used to calibrate the model, which was subsequently validated on other years. Paucity of data in mountainous regions necessitated a model that required few measured variables to be developed. Distinctive seasonal water temperature regime was identified for larger rivers which drain relatively steep catchments, with substantial basin ice coverage. Such a regime is not replicated in streams draining smaller glaciers with lower gradients. Patterns in diurnal ranges of temperature in rivers draining large glaciers have been identified, temperature ranges reducing during days with high radiation and rising riverflows. Stream surface area was found to be the main catchment characteristic influencing temperature in glacier-fed rivers. Measured stream albedo values suggest that surface reflectivity is unlikely to be a major control on water temperature. Stream temperatures simulated by the model demonstrate high fidelity to those measured in the field. The temperature of glacier-fed streams will increase as climate warms as the distance over which heating can occur will lengthen as glaciers retreat, despite volume of flow being augmented by the deglaciation discharge dividend.

Precipitation and temperature variations affecting glacierised Himalayan headwaters and water resources in the upper Indus and Sutlej basins

AGU Fall Meeting Abstracts, Dec 1, 2013

Drone based Quantification of Channel Response to an Extreme Flood for a Piedmont Stream

AGU Fall Meeting Abstracts, Dec 1, 2019

The influence of extreme floods on the form and functioning of upland systems has concentrated on... more The influence of extreme floods on the form and functioning of upland systems has concentrated on the erosive impact of these flows. They are seen to be highly competent with coarse sediment transport rates limited by upstream supply and moderated by the 'blanketing' effect of an armour layer. This study investigates the effect of extreme events on the upland sediment cascade subjected to a recent extreme rainfall-induced flood event. The drone-based survey generated orthophotography and a DEM surface, which was compared with historic LiDAR data. This allowed erosion and deposition to be quantified and the surface micro-variation used to characterise stable and mobile sediment. The idealised model of sediment residence time increasing downstream is questioned by the findings of this study as relatively little coarse bedload sediment appears to have been transferred downstream in favour of initial local channel erosion (moderated by legacy large sediment), mid-reach palaeo-channel reactivation, sub-channel infilling and downstream deposition of the majority of mobilised sediment across berm and bar surfaces within the active inset channel margins. Channel margin erosion was largely limited to fine sediment stripping moderated by the re-exposure of post-glacial sediment. Only a weak relationship was found between local channel slope and deposition, with storage linked more to the presence of inset berm and bar areas within the inset active channel. Downstream fining of sediment is apparent as is a strong contrast between coarser active sub-channels and finer bar and berm areas.

Ten years after the flood: a case of extended geomorphic convalescence in an upland stream

AGUFM, Dec 1, 2017

Modelling spatially distributed vegetation roughness change in a bedrock channel using LiDAR; hydraulic and morphological implications

AGU Fall Meeting Abstracts, Dec 1, 2016

Reach-Scale Hydraulic Influence on Sediment Dynamics and Morphological Development in a Bedrock Influenced River

2014 AGU Fall Meeting, Dec 17, 2014

Climatic Variation And Runoff From Himalayan Mountain Basins

AGU Fall Meeting Abstracts, Dec 1, 2012

Radiometric calibration of a dual-wavelength terrestrial laser scanner using neural networks

Remote Sensing Letters, Jan 14, 2016

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 Intern... more

Using 2D Sediment Modelling to Simulate Geomorphic Change for River Restoration Initiatives

&lt;p&gt;River restoration projects have long relied on the use of modelling in both 1D a... more &lt;p&gt;River restoration projects have long relied on the use of modelling in both 1D and 2D to simulate the changes to flow hydraulics and flood extent that alterations to a river and floodplain will have caused. These methods have grown more accurate with increasing computing power and more complex software. However, despite the developments in modelling, a significant gap remains in the usage and accuracy of sediment modelling to identify arguably one of the most important metrics of river restoration: Geomorphic Change. Therefore, this paper attempts to address this by investigating the accuracy of high-resolution sediment modelling to identify geomorphic change on Blaze Beck in Cumbria, a high energy wandering river system that has recently been restored. Comparisons have been made between the impacts of a simulated flood event created using HEC-RAS 6.1 modelling software and a real-life flood event on October the 27&lt;sup&gt;th&lt;/sup&gt; 2021, to compare changes to geomorphology and identify the degree of accuracy of the 2D change modelling compared to change measured using drone-based photogrammetry. The results appear generally accurate, predicting locations of head cutting and more general low-level erosion and deposition. Bar formation, splay deposition and general bed raising are all predicted. The model is, however, very sensitive to the gradation of sediment it has been trained with and this can skew the ratio and pattern of deposition and erosion depending on the sample data used to simulate real life conditions. The model, once refined and iterated to best simulate potential change, is functional even in a high energy hydraulically diverse environment like Blaze Beck, and will have significant value in predicting the degree to which geomorphic change will occur because of restorative or other changes to a river reach.&lt;/p&gt;

Development of a Novel, Parsimonious, Model-based Approach for Representing High-resolution Gravel Facies

2D Biotope Mapping Using Combined LIDAR, Topographic Survey And Segmented 1D Flow Modelling

ABSTRACT Reach averaged habitat availability models such as PHABSIM are limited due principally t... more ABSTRACT Reach averaged habitat availability models such as PHABSIM are limited due principally to their failure to adequately map hydraulic habitat distribution at a representative scale. A lack of morphologic data, represented in the form of sparse geometric cross-sections fails to generate the necessary detail. Advances in data collection, improved spatial modelling algorithms and the advent of cross-section based segmentation routines in 1D hydraulic models provides the opportunity to revisit the issue of hydraulic habitat mapping and modelling. This paper presents a combined technique for habitat characterisation at the sub-bar scale is presented for the River Rede, Northumberland, UK. Terrestrial LIDAR data of floodplain, banks and exposed bar surfaces at an average 0.05 m spacing are combined with sparser total station survey data of submerged morphologic features. These data are interpolated to create a uniform DEM grid at 0.2 m spacing (adequate to detect the smallest variation in hydraulic habitat in this system). The data grid were then imported into the HECRAS 1D hydraulic model to generate a 2 m spaced series of cross-sections along a 220 m sinuous single thread reach exhibiting pool - riffle point-bar morphology. The hydraulic segmentation routine then generated estimates of depth averaged flow velocity, flow depth and sub unit discharge for 40 sub-divisions of the flow width for a series of flows from 0.5 m3s-1 up to bankfull flow of approximately 9 m3s-1. The resultant hydraulic data were exported in the project coordinate system and plotted to reveal the 2D pattern of hydraulic biotopes present across the range of flows modelled. The results reveal broadly realistic patterns consistent with previous empirical studies and compare well with LIDAR based biotope maps. Analysis of the temporal pattern of biotope change indicates that biotope diversity and complexity is at a maximum at lower flows and across shallower area (riffles) and that these dominate the temporal biotope pattern revealing the importance of the low flow regime in generating and maintaining habitat diversity. The combined survey and modelling technique presented here offers a viable new approach to habitat mapping and modelling providing predictive capability when assessing changes to river morphology and flow regime.

Spatial variability of glacier decline in the Indian and Nepalese Himalaya since the 1960s

Precipitation and temperature variations affecting glacierised Himalayan headwaters and water resources in the upper Indus and Sutlej basins

Biotope mapping using combined LIDAR acoustic doppler velocity profiler survey

Role of hydrology in managing consequences of a changing global environment, 2010

Real Rivers: Defining the Natural Poster

AGU Fall Meeting 2021, Dec 16, 2021

EVIDENCE OF NON-CONTIGUOUS FLOOD DRIVEN COARSE SEDIMENT TRANSFER AND IMPLICATIONS FOR SEDIMENT MANAGEMENT

by David Milan, george heritage, and Neil Entwistle

Proceedings of the 38th IAHR World Congress, Panama, September 1-6 Sept, 2019, Panama City, Panama, 2019

We investigate gravel redistribution and morphological response of three headwater streams follow... more We investigate gravel redistribution and morphological response of three headwater streams following the Storm Desmond floods of December 2015. Reactive management of the watercourses following the flooding concentrated on removal of gravel and clearing of vegetation, perceived as having been significant causes of local flooding. Aerial LIDAR and ortho-photography were employed to critically assess the location, type and magnitude of sediment mobilization, using an sUAV to capture imagery of lake sediment fans across the area. Whilst gravel was mobilized during the flood the volumes involved do not appear to be as high as anticipated, with little detectable change in lake fan deposits in the sink zone of the three study streams. Re-exposure of relict gravels on floodplains through stripping of surface vegetation and soils, gave the false impression of fresh deposition. Reactivation of wandering channel zones appear to have acted as buffers to large-scale sediment movement rather than acting as supply zones. Sediment accumulation through towns and villages was harder to quantify due to the rapid clean-up operation, however, the authors suggest that this may not be as large as assumed and the widespread dredging is likely to have caused more problems than it has solved as the bed of many watercourses is now highly susceptible to mobilisation following mechanical disruption of the previously strongly armoured surface.

An investigation of the role of geomorphology in influencing biotope distribution.

by David Milan and Neil Entwistle

. In M. Thoms, K. Heal, E. Bogh, A. Chambel and V. Smakthin (Eds), Ecohydrology of surface and groundwater dependent systems: concepts, methods and recent developments. Proc. of JS.1 at the Joint IAHS & IAH Convention, Hyderbad, India, September 2009. IAHS Publ. 328, 68-76., 2009

Riffle-pool-point bar sequences provide the template for a number of aquatic habitats. Water flow... more Riffle-pool-point bar sequences provide the template for a number of aquatic habitats. Water flowing over these morphologies generates spatial hydraulic variation over a rivers flow regime resulting in a changing mosaic of hydraulic habitats or biotopes. Little attention has been given to the explicit spatial and temporal distribution of biotopes in relation to channel morphology. This study uses terrestrial LiDAR data to map biotope distribution at two discharges. A link was found between the riffle units and key characteristic biotopes. Biotope type change was also broadly consistent over this scale but areal coverage varied between units. It is argued that management options for such river systems targeted at maintaining the gross morphology will succeed in creating a variety of hydraulic biotopes that are consistent in their types across riffles; however, distribution and dominance are likely to be controlled by more local factors such as bed material and channel slope.

Temporal change in hydraulic habitat inferred from a high resolution 2D flow modelling approach.

by David Milan, Neil Entwistle, and george heritage

BHS third international Symposium, Managing Consequences of a Changing Global Environment, Newcastle University, July 21-23, 2010., 2010

Reach averaged habitat availability models fail to adequately predict hydraulic habitat distribut... more Reach averaged habitat availability models fail to adequately predict hydraulic habitat distribution at a representative scale, due principally to a lack of morphologic data. Advances in data collection, spatial modelling and the development of 2D hydraulic models provide the opportunity to map hydraulics across an entire reach at the sub-bar scale. This paper presents a technique for habitat characterisation for the River Wharfe, North Yorkshire, UK, where terrestrial LIDAR data of subaerial surfaces are combined with sparser Acoustic Doppler Velocity Profiler survey data of submerged features to create a 0.2 m resolution digital elevation model. This was imported into the River2D hydraulic model and run with a series of discharges up to bankfull flow. The mapped biotope patterns are consistent with previous subjective studies conducted at the bar scale and the low flow pattern compares well with the distribution calculated from measured depth and velocity data. The temporal pattern of biotope change indicates that diversity and complexity is at a maximum at lower flows across riffles and that this is the dominant pattern across the flow regime. Physical habitat / biotope diversity is increased as new morphology is inundated and becomes part of the wetted channel. These new biotope areas are transient and the maintenance of low flows is essential to maintaining habitat diversity. The new technique offers a viable and easily applied approach to habitat quantification and prediction at a scale appropriate to in-stream ecology.

Terrestrial laser scanning for hydraulic habitat mapping and restoration in the fluvial environment.

by David Milan, Neil Entwistle, and george heritage

River Restoration Conference Proceedings, University of Nottingham, 1-2 April 2009. , 2009

The purpose of river restoration is to achieve improvements in physical, vegetative and hydraulic... more The purpose of river restoration is to achieve improvements in physical, vegetative and hydraulic habitat in damaged or poor quality river systems. There is an increasing requirement for post project monitoring and assessment of the quality of river restoration schemes in terms of morphology, sedimentology and hydraulics. This is often difficult for many reasons including appraiser subjectivity, stage-dependent hydraulics and assessment being focused on different key species depending on the discipline of the appraiser and the basis for the assessment. Recent developments in Terrestrial Laser Scanning (TLS) technology means that it is now possible to measure and represent the physical environment in a high degree of spatial resolution. This paper demonstrates a new approach to biotope definition using high resolution spatial data defining water surface roughness for a representative reach of the River Skirfair, Yorkshire, UK, collected using TLS. It is clear from the mapped data that biotope distribution is more complex than previously recorded using subjective techniques, and results obtained may provide a basis for a quantitative alternative to the current classification system employed by the river habitat survey. The successful biotope demonstration indicates that TLS can be utilised to measure water surface roughness, and map hydraulic diversity and indicates that the technique can be a very useful tool for river restoration scientists.

Biotope mapping using combined LiDAR and acoustic doppler profiler survey.

by David Milan, Neil Entwistle, and george heritage

BHS third international Symposium, Managing Consequences of a Changing Global Environment, Newcastle University, July 21-23, 2010. , 2010

The identification and mapping of in-stream ecological units is largely a subjective exercise due... more The identification and mapping of in-stream ecological units is largely a subjective exercise due to the lack of appropriate field survey instruments that can capture detail at the relevant spatial and temporal scales. This paper presents a combined survey technique for habitat characterisation at the sub-bar scale developed and tested on the River Wharfe, North Yorkshire, UK. Terrestrial LiDAR data of the water surface are combined with Acoustic Doppler Velocity Profiler survey data of submerged morphologic features and velocities to generate a detailed hydraulic and geometric data set including local depth, local bed roughness, segmented velocity readings and cross-sectional discharge. The data are used to calculate ecologically relevant parameters, including Froude and Reynolds numbers, which in turn reveal realistic biotope patterns that are consistent with previous empirical studies conducted at the morphologic unit scale. In-stream habitat complexity across morphologic units is high and suggests that patterns of biotope distribution may be more complex than previously suggested. The combined survey approach presented here offers a viable new approach to habitat measurement and mapping at a scale appropriate to in-stream ecology and demonstrates a complexity that is overlooked using visual mapping techniques.

Mapping hydraulic biotopes using terrestrial laser scan data of water surface properties.

by David Milan, Neil Entwistle, and george heritage

Earth Surface Processes & Landforms, 35, 918-931., 2010

For more than a decade, habitat mapping using biotopes (in-channel hydraulically-defined habitats... more For more than a decade, habitat mapping using biotopes (in-channel hydraulically-defined habitats) has underpinned aquatic conservation in the UK through (a) providing baseline information on system complexity and (b) allowing environmental and ecological change to be monitored and evaluated. The traditional method used is the subjective river habitat or corridor survey. This has recently been revised to include the floodplain via GeoRHS, but issues still exist concerning development of a national database due to the labour intensive nature of the data collection, subjectivity issues between samplers, temporal changes, the fuzzy nature of perceived habitats and habitat boundaries. This paper takes an innovative approach to biotope definition using high resolution spatial data to define water surface roughness for two representative reaches of the River South Tyne, Cumbria, and the River Rede, Northumberland, UK. Data was collected using a terrestrial laser scanner (TLS) and hydraulic variability simply expressed through assigning a local standard deviation value to a set of adjacent water surface values. Statistical linkage of these data with biotope locations defined visually in the field allowed complete mapping of the surveyed reach defining habitat and biotope areas to the fine scale resolution of the TLS data. Despite issues of data loss due to absorption and transmission through the water, the reflected signal generated an extremely detailed and objective map of the water surface roughness, which may be compared with known biotope locations as defined by visual identification in the field. The TLS accuracy achieved in the present study is comparable with those obtained using hyperspectral imagery: with 84% of the pool/glide/marginal deadwater amalgamated biotope, 88% of riffles, 57% of runs and 50% of the amalgamated cascade/rapid biotope successfully plotted. It is clear from this exercise that biotope distribution is more complex than previously mapped using subjective techniques, and based upon the water surface roughness delimiters presented in this study, the amalgamation of pools with glides and marginal deadwaters, riffles with unbroken standing waves, and cascades with rapids, is proposed. Copyright © 2010 John Wiley & Sons, Ltd

Relationship between turbulent flow structure and biotopes in an upland trout stream.

by David Milan, Neil Entwistle, and george heritage

Proceedings of the 7th International Symposium on Ecohydraulics, Concepción, Chile, January 12-16, 2009., 2009

This study interrogates biotope categorization through the application of a 3D hydraulic model. T... more This study interrogates biotope categorization through the application of a 3D hydraulic model. The study concentrates on a 60 m reach of the River Rede in Northumberland, UK, that provides habitat for brown trout (Salmo trutta L.), brook lamprey (Lampetra planeri L.) and bull head (Cottus gobio L.). Analysis of the population of simulated turbulent flow properties within each biotope may help in isolating biotopes. Biotope maps for the Rede study reach are presented based upon the 10 th and 90 th percentile of populations of turbulent flow variables, which compare well with independently surveyed biotope coordinates. Available habitat is also mapped for the three key species based upon published velocity limits, and comparisons are made with the spatial distribution of biotopes within the reach. Lamprey ammocoete habitat equated to 46% of the available reach area, and showed similar spatial coverage to glide and margin biotopes. Hydraulic habitat for the adult bullhead and brown trout parr is very similar, concentrating in riffle and rapid biotopes, with available areas of 29% and 37% respectively.

An assessment of temporal habitat availability in a gravel-bed river using a LiDAR–derived CFD model.

by David Milan, Neil Entwistle, and george heritage

In . Thoms, K. Heal, E. Bogh, A. Chambel and V. Smakthin (Eds), Ecohydrology of surface and groundwater dependent systems: concepts, methods and recent developments. Proc. of JS.1 at the Joint IAHS & IAH Convention, Hyderbad, India, September 2009. IAHS Publ. 328, 53-61., 2009

Riffle-pool sequences in gravel-bed rivers provide the template for a number of fish and inverteb... more Riffle-pool sequences in gravel-bed rivers provide the template for a number of fish and invertebrate habitats. Water flowing over these morphologies create spatial hydraulic variation over a rivers flow regime that are logistically impossible to measure in the field. This paper utilises the FLUENT Computational Fluid Dynamics (CFD) model to construct a 0.2 m DEM for a 180 m reach of Kingsdale Beck, UK. CFD modelling allows spatial estimation of flow hydraulics for flows up to bankfull. With increasing discharge complex patterns of hydraulic variation are revealed that exists within larger macroscale flow structures. During elevated flows these could act as biotic refugia. The spatial distribution and areal extent of habitat refugia for two commonly occurring macroinvertebrate species: Gammerus pulex (Amphipoda, Crustacea) and Ephemerella ignite (Ephemeroptera, Insecta), are explored for three discharges from baseflow up to bankfull. Temporal modelling permitted mapping of these refugia across the flow regime.

Utilisation of terrestrial laser scanning for hydraulic habitat mapping.

by David Milan, Neil Entwistle, and george heritage

Proceedings of the 7th International Symposium on Ecohydraulics, Concepción, Chile, January 12-16, 2009., 2009

For more than a decade, habitat mapping using biotopes (in-channel hydraulicallydefined habitats)... more For more than a decade, habitat mapping using biotopes (in-channel hydraulicallydefined habitats) has underpinned aquatic conservation in the UK providing baseline information on system complexity and allowing the effect of environmental and ecological change to be monitored and evaluated. Traditionally the principal technique used is the river habitat or corridor survey, consisting of a subjective mapping of the river and an adjacent thin linear strip of land in 500 m segments. This paper takes a new approach to biotope definition using high resolution spatial data defining water surface roughness for a representative reach of the River Skirfair, Yorkshire, UK, collected using a Terrestrial Laser Scanner (TLS). Statistical linkage of these data with biotope locations defined visually in the field allows complete mapping of the surveyed area defining habitat and biotope areas to the fine scale resolution of the TLS data. Despite issues of signal loss due to absorption and transmission through the water the reflected signal generates an extremely detailed and accurate objective map of the water surface roughness that may be compared to known biotope locations as defined by visual identification in the field. It is clear from this comparison that biotope distribution is more complex than previously mapped using subjective techniques and calls into question the current classification system employed by the river habitat survey.

Detecting grain roughness change and sorting patterns in a gravel-bed river using terrestrial laser scanning.

by David Milan and Neil Entwistle

Poster presented at Gravel Bed Rivers 7, Tadoussac, Québec, Canada, 6-10 September 2010. , 2010