Assessing surface flow pathway connectivity in semi-natural unimproved grasslands using structure from motion

2020 ◽  
Author(s):  
Nicola Ellis ◽  
Richard Brazier ◽  
Karen Anderson
Keyword(s):  
Structure From Motion ◽  
Prescribed Burning ◽  
Flood Management ◽  
Drainage Density ◽  
Surface Flow ◽  
Airborne Lidar ◽  
Pathway Length ◽  
Flow Pathways ◽  
Hydrological Functioning ◽  
Flow Pathway

<p>In addition to providing a valuable habitat, semi-natural unimproved grasslands may have significant value as part of natural flood management strategies. However, further understanding of the hydrological functioning of these landscapes is required and this study is developing new methods for using proximal remote sensing techniques to assess surface flow pathway connectivity.</p><p>Purple moor grass (<em>Molinia caerulea</em>) dominated fields are seasonally saturated and have a dense tussock structure, hypothesised to result in long surface flow pathways with low hydrological connectivity and greater surface roughness than neighbouring intensively managed improved grassland. Quantifying these surface flow pathways required fine-scale understanding of topography not available from available datasets such as airborne LiDAR. After prescribed burning (a local management practice) at a study site in South West England, the underlying <em>M. caerulea</em> tussock structure and flow pathways were exposed. A DJI Mavic Air quadcopter was flown over the <em>M. caerulea</em> field shortly after to capture this structure. A neighbouring improved grassland field of similar size and slope was also surveyed.</p><p>Drone surveys were carried out using an automated flight path over an area of 1.7ha of <em>M. caerulea</em> and 2.2 ha of improved grassland. Imagery was captured with an overlap/sidelap of 85% and with a ground sampling distance of 25m. Ground control points were geolocated, using a GNSS with an accuracy of ~0.03m to constrain subsequent structure from motion (SFM) photogrammetry processing.</p><p>SFM was used to create dense point clouds, from which digital surface models (DSM) of the two sites were derived at a resolution of 0.03m. The standard deviation of points within each DSM grid cell was also calculated to describe the uncertainty resulting from converting point cloud data to raster. An automated classification method was developed, in R using the LidR package, to identify individual <em>M. caerulea</em> tussocks. The edges of tussocks were characterised by greater error due to the variability in topography and therefore could be used to identify tussock features.</p><p>The resulting DSMs were used to quantify surface flow pathway length in both sites using the Arc GIS flow routing algorithm. This included flow pathway length and drainage density (length of flow path per unit area). <em>M. caerulea</em> had longer, more sinuous surface flow pathways through the dense tussocks, with an average drainage density of 2.54m m¯². This was significantly greater than drainage density in the improved field (1.82m m¯²). Flow pathways in the improved grassland were straighter and more in-line with the slope in comparison. Longer, tenuous surface flow pathways in <em>M. caerulea</em> sites theoretically result in a slower velocity of surface runoff, reduced soil erosion, greater evapotranspiration and root uptake than improved grassland sites. It is proposed that this understanding will be incorporated into hydrological modelling to improve understanding of the hydrological functioning and possible natural flood management potential of these landscapes.</p>

Reducing Nutrient Loads in Northern Irish Catchments: A Modelling Approach Based on Load Apportionment and Flow Pathway Identification

2021 ◽  
Author(s):  
Russell Adams ◽  
Donnacha Doody
Keyword(s):  
Water Quality ◽  
Large Scale ◽  
Agricultural Land ◽  
Assessment Tool ◽  
Ecological Status ◽  
Point Sources ◽  
Load Reduction ◽  
Nutrient Loads ◽  
Flow Pathways ◽  
Flow Pathway

<p>Northern Ireland has been somewhat overlooked in terms of water quality modelling in the past. Many of its catchments have consistently failed to meet Water Framework Directive targets especially due to high levels of dissolved nutrients and poor ecological status. A catchment based modelling study to address this issue has not been undertaken here previously and the approach described here uses two water quality models to achieve this aim. The objectives of the modelling were firstly to identify the total load reductions (in terms of Phosphorus (P)) required to reduce in-stream loadings sufficiently for concentrations of soluble reactive P (SRP) to be reduced to achieve the WFD “Good” status levels, and secondly to split these loadings into diffuse and point components. The third objective was to identify the most likely flow pathways for the transport of the diffuse component of P to the watercourses particularly for the agricultural (mostly intensive grassland farming) land use which dominates in almost all NI catchments.</p><p>The first model applied is the Source Load Apportionment Model (SLAM) developed by the Irish EPA. This model provides a large-scale assessment of the point and diffuse load components across catchments where multiple pressures are occurring. The second model us the Catchment Runoff Flux Assessment Tool (CRAFT) which is able to back-calculate nutrient loads associated with three major flow pathways. SLAM is a static model which uses averaged loadings from diffuse agriculture and non-agricultural land uses, and point sources (where information can be obtained from various sources) to calculate N and P exports. For P, the agricultural diffuse load component uses an enhanced version of the export coefficient approach based on combining the sources of P from applied nutrients (slurry and fertiliser) and soil P. A modelling tool allows the user to evaluate load reduction scenarios where one or several components of P (both point and diffuse) are adjusted downwards to achieve the catchment’s required load reduction. The CRAFT model works on a dynamic (daily) modelling scale and has simulated sub-catchments where the SLAM model has identified the need for significant load reductions. It identifies the different reductions (P export) that are required for each flow pathway, which will then inform on the type of additional measures (e.g. sediment traps, riparian buffer strips and wetlands) that may also be required.</p><p>The initial aim of this study is to complete a pilot application to the trans-border (UK and ROI) Blackwater catchment (1360 km<sup>2</sup>). Through a review of alternative modelling options for the whole area of NI, an assessment of whether this approach is suitable for application to the entire territory can be made.</p>

Developing an Algorithm for Urban Flood Management With the Aim of Reducing Damage and Costs Using the Concept of Conditional Value at Risk 

2021 ◽  
Author(s):  
Pedram Eshaghieh Firoozabadi ◽  
sara nazif ◽  
Seyed Abbas Hosseini ◽  
Jafar Yazdi
Keyword(s):  
At Risk ◽  
Hybrid Model ◽  
Best Management Practices ◽  
Value At Risk ◽  
Management Practices ◽  
Flood Management ◽  
Surface Flow ◽  
Conditional Value At Risk ◽  
Urban Flood ◽  
Proposed Model

Abstract Flooding in urban area affects the lives of people and could cause huge damages. In this study, a model is proposed for urban flood management with the aim of reducing the total costs. For this purpose, a hybrid model has been developed using SWMM and a quasi-two-dimensional model based on the cellular automata (CA) capable of considering surface flow infiltration. Based on the hybrid model outputs, the best management practices (BMPs) scenarios are proposed. In the next step, a damage estimation model has been developed using depth-damage curves. The amount of damage has been estimated for the scenarios in different rainfall return periods to obtain the damage and cost- probability functions. The conditional value at risk (CVaR) are estimated based on these functions which is the basis of decision making about the scenarios. The proposed model is examined in an urban catchment located in Tehran, Iran. In this study, five scenarios have been designed on the basis of different BMPs. It has been found that the scenario of permeable pavements has the lowest risk. The proposed model enables the decision makers to choose the best scenario with the minimum cost taking into account the risk associated with each scenario.

scholarly journals A new stream and nested catchment framework for Australia

2013 ◽  
Vol 10 (12) ◽  
pp. 15433-15474
Author(s):  
J. L. Stein ◽  
M. F. Hutchinson ◽  
J. A. Stein
Keyword(s):  
Spatial Scales ◽  
Surface Flow ◽  
Stream Network ◽  
Australian Water ◽  
Assessment Tasks ◽  
Australian Continent ◽  
Wide Range ◽  
High Conservation ◽  
Flow Pathways ◽  
Fully Connected

Abstract. Nationally framed assessment and planning assists coordination of resource management activities across jurisdictional boundaries and provides context for assessing the cumulative effects of impacts that can be underestimated by local or regional studies. However, there were significant shortcomings in the existing spatial frameworks supporting national assessment and planning for Australia's rivers and streams. We describe the development of a new national stream and nested catchment framework for Australia that includes a fully connected and directed stream network and a nested catchment hierarchy derived using a modified Pfafstetter scheme. The directed stream network with associated catchment boundaries and Pfafstetter coding respect all distributary junctions and topographically driven surface flow pathways including across the areas of low relief and internal drainage that make up over half of the Australian continent. The Pfafstetter coding facilitates multi-scale analyses and easy tracing and query of upstream/downstream attributes and tributary/main stem relationships. Accompanying the spatial layers are 13 lookup tables containing nearly 400 attributes describing the natural and anthropogenic environment of each of the 1.4M stream segments across the Australian continent at multiple spatial scales (segment, sub-catchment and catchment). The database supplies key spatial layers to support national water information and accounting needs and assists a wide range of research, planning and assessment tasks at regional and continental scales. These include the delineation of reporting units for the Australian Water Resources Assessment, the development of an ecohydrological environment classification for Australian streams and the identification of high conservation value aquatic ecosystems for northern Australia.

scholarly journals ASSESSMENT OF VULNERABILITY IN AGRICULTURAL LAND IN FLOOD PRONE AREAS AND APPLICATION OF MOBILE SMART PHONE IN PROVIDING FLOOD HAZARD INFORMATION IN LAM RIVER BASIN (VIETNAM)

2021 ◽  
Vol 13 (2) ◽  
pp. 254-264
Author(s):  
Nguyen DUNG ◽  
◽  
Dang MINH ◽  
Bui AN ◽  
Nguyen NGA ◽  
...  
Keyword(s):  
River Basin ◽  
Agricultural Land ◽  
Flood Hazard ◽  
Smart Phone ◽  
Flood Management ◽  
Drainage Density ◽  
Slope Length ◽  
Risk Levels ◽  
High Hazard ◽  
Very High

Floods are considered to be one of the most costly natural hazards in the Lam river basin causing infrastructure damages as well as devastating the affected area and relatively high death toll. So prevention is necessary for shielding lives and properties. The flood management on the Lam River basin has been considering for many years to minimize damages caused by flooding. The flood hazard zoning map is one of the indispensable tools to provide information about hazard and risk levels in a particular area and to perform the necessary preventive and preparedness procedures. The multicriteria decision analysis based on geographic information systems is used to build a flood hazard map of the study area. The analytic hierarchy process is applied to extract the weights of six criteria affecting the areas where are prone to flooding hazards, including rainfall, slope, relative slope length, soil, land cover, and drainage density. The results showed in 91.32 % (20103.83 km2) of the basin located in the moderate hazard zones to very high hazard zones. Accordingly, this study also determined 4 vulnerability levels to agricultural land including low, medium, high, and very high. About 94% of the total area of agricultural land in the basin are classified into moderate to the very high hazard of flood vulnerability. The paper presents a method that allows flood risk areas in the Lam River basin to receive information about flood risks on a smartphone, making them more aware.

scholarly journals Dune migration and volume change from airborne LiDAR, terrestrial LiDAR and Structure from Motion-Multi View Stereo

2020 ◽  
Vol 143 ◽  
pp. 104569 ◽  
Author(s):  
Carlos H. Grohmann ◽  
Guilherme P.B. Garcia ◽  
Alynne Almeida Affonso ◽  
Rafael Walter Albuquerque
Keyword(s):  
Volume Change ◽  
Structure From Motion ◽  
Airborne Lidar ◽  
Terrestrial Lidar ◽  
Dune Migration

Multi-objective optimisation of cost–benefit of urban flood management using a 1D2D coupled model

2011 ◽  
Vol 63 (5) ◽  
pp. 1053-1059 ◽  
Author(s):  
S. W. Delelegn ◽  
A. Pathirana ◽  
B. Gersonius ◽  
A. G. Adeogun ◽  
K. Vairavamoorthy
Keyword(s):  
Flow Model ◽  
Coupled Model ◽  
Cost Benefit ◽  
Flood Management ◽  
Flood Damage ◽  
Surface Flow ◽  
Nsga Ii ◽  
Urban Flood ◽  
Multi Objective ◽  
Evolutionary Optimisation

This paper presents a multi-objective optimisation (MOO) tool for urban drainage management that is based on a 1D2D coupled model of SWMM5 (1D sub-surface flow model) and BreZo (2D surface flow model). This coupled model is linked with NSGA-II, which is an Evolutionary Algorithm-based optimiser. Previously the combination of a surface/sub-surface flow model and evolutionary optimisation has been considered to be infeasible due to the computational demands. The 1D2D coupled model used here shows a computational efficiency that is acceptable for optimisation. This technological advance is the result of the application of a triangular irregular discretisation process and an explicit finite volume solver in the 2D surface flow model. Besides that, OpenMP based parallelisation was employed at optimiser level to further improve the computational speed of the MOO tool. The MOO tool has been applied to an existing sewer network in West Garforth, UK. This application demonstrates the advantages of using multi-objective optimisation by providing an easy-to-comprehend Pareto-optimal front (relating investment cost to expected flood damage) that could be used for decision making processes, without repeatedly going through the modelling–optimisation stage.

scholarly journals Groundwater, flooding and hydrological functioning in the Findhorn floodplain, Scotland

2014 ◽  
Vol 45 (6) ◽  
pp. 755-773 ◽  
Author(s):  
A. M. MacDonald ◽  
D. J. Lapworth ◽  
A. G. Hughes ◽  
C. A. Auton ◽  
L. Maurice ◽  
...  
Keyword(s):  
Flood Management ◽  
Discharge Zone ◽  
Low Permeability ◽  
Intense Rainfall ◽  
Groundwater Response ◽  
Management Schemes ◽  
The 19Th Century ◽  
Hydrological Functioning ◽  
Daily Total

A large floodplain of the River Findhorn, northeast Scotland, was investigated using hydrogeological and hydrochemical methods (including residence time indicators) to characterise groundwater/surface-water coupling and groundwater flooding. The study demonstrated widespread stratification within the floodplain: shallow (<8 mbgl) deposits are highly permeable (100 m/d); deeper deposits have low permeability (1 m/d) and limit interaction with the underlying sandstone aquifer. Hydrochemistry and groundwater-level variations show floodplain groundwater is recharged from the river, surrounding hillslopes and direct rainfall infiltration. The river loses water to groundwater as it enters the floodplain; further downstream, groundwater response follows closely river stage giving rise to complex exchanges; near the sea, groundwater continually discharges to rivers, tributaries and ditches. Groundwater flow is largely parallel to the river and mean groundwater residence times vary from 3 years to 20 years. Groundwater at the edge of the floodplain, close to the hillslopes, has distinctive chemistry and responds rapidly to local intense rainfall (daily total >30 mm). Persistent groundwater flooding occurs within topographical lows and also in the discharge zone where it is largely managed with a series of drains constructed in the 19th century. The significant and complex role of groundwater in floodplains, demonstrated by this study, highlights the importance of fully considering groundwater in flood management schemes.

scholarly journals Applicability of an integrated plume rise model for the dispersion from wild-land fires

2014 ◽  
Vol 7 (6) ◽  
pp. 2663-2681 ◽  
Author(s):  
J. Kukkonen ◽  
J. Nikmo ◽  
M. Sofiev ◽  
K. Riikonen ◽  
T. Petäjä ◽  
...  
Keyword(s):  
Field Experiments ◽  
Prescribed Burning ◽  
Meteorological Data ◽  
Inversion Layer ◽  
Atmospheric Dispersion ◽  
Heat Fluxes ◽  
Airborne Lidar ◽  
Plume Rise ◽  
Buoyant Plume ◽  
Model Predictions

Abstract. We have presented an overview of a mathematical model, BUOYANT, that was originally designed for the evaluation of the dispersion of buoyant plumes originated from major warehouse fires. The model addresses the variations of the cross-plume integrated properties of a buoyant plume in the presence of a vertically varying atmosphere. The model also includes a treatment for a rising buoyant plume interacting with an inversion layer. We have compared the model predictions with the data of two prescribed wild-land fire experiments. For the SCAR-C experiment in Quinault (US) in 1994, the predicted vertical extents of the plume at maximum plume rise were between 500 and 800 m and between 200 and 700 m, using two alternative meteorological data sets. The corresponding observed injection heights of the aerosol particles measured using an airborne lidar (light detection and ranging) ranged from 250 to 600 m. For the prescribed burning experiment in Hyytiälä (Finland) in 2009, the model predictions were compared with plume elevations and diameters, determined based on particulate matter number concentration measurements onboard an aeroplane. However, the agreement between modelled and measured results substantially depends on how the properties of the source term are evaluated, especially regarding the convective heat fluxes from the fire. The results demonstrate that in field experiments on wild-land fires, there are substantial uncertainties in estimating both (i) the source terms for the atmospheric dispersion computations and (ii) the relevant vertical meteorological profiles.

scholarly journals Evaluation of Flood Management in Nigeria: A Case Study of Yauri Local Government Area, Kebbi State

2019 ◽  
pp. 652-659
Author(s):  
Daniel Habila Galadima ◽  
Ishaya K. Samaila ◽  
Magaji I. Joshua
Keyword(s):  
Local Government ◽  
Flood Management ◽  
Drainage Density ◽  
Local Government Area ◽  
Data Set ◽  
Topographical Map ◽  
Gis Environment ◽  
High Flood ◽  
Pair Wise Comparison

An evaluation of management in Nigeria with focus on Yauri Local Government Area of Kebbi State was carried out. The study made use of ASTER data of 2017 with spatial resolution of 30m, topographical map at a scale of 1:50,000, monthly rainfall data for 35 covering the study area and soil map at a scale of 1:50,000. Thematic maps for soil, rainfall and elevation were produced converted to raster data in GIS environment. Each data set in a single map was given weight by pair-wise comparison; reclassification of each map was done based on the weights generated from the pair-wise comparison of each dataset. The weights generated revealed that rainfall with 46 as its weight has the greatest influence on flood occurrences in the study area. Elevation accounted for weights of 24, slope accounted for 12 while drainage density, soil and LULC accounted for 10, 8 and 3 respectively. The settlements of Gumbi, Yauri, Unguwa Damisa, Zamare and Jijima that make up the study area lie along the zone of very high flood vulnerable land. Among the causes of flooding, excess rainfall and coastal location of the various settlements are responsible for flooding. Besides, the relief of the study area is such that encourage flooding as all the settlements are situated along the river course. The predominant coping and adapting strategies adopted to check flooding in the study area are temporary relocation and the raising of the floor of their houses among others.

scholarly journals Exploring the Capability of Natural Flood Management Approaches in Groundwater-Dominated Chalk Streams

Water ◽  
2021 ◽  
Vol 13 (16) ◽  
pp. 2212
Author(s):  
Imogen Barnsley ◽  
Rebecca Spake ◽  
Justin Sheffield ◽  
Julian Leyland ◽  
Tim Sykes ◽  
...  
Keyword(s):  
Positive Impact ◽  
Flood Management ◽  
Evidence Base ◽  
Hydrological Models ◽  
Headwater Catchments ◽  
Management Interventions ◽  
Management Application ◽  
Flow Pathways ◽  
Chalk Streams ◽  
Management Approaches

This study aims to address the gap in the Natural Flood Management (NFM) evidence base concerning its implementation potential in groundwater-dominated catchments. We generated a typology of 198 chalk catchments using redundancy analysis and hierarchical clustering. Three catchment typologies were identified: (1) large catchments, (2) headwater catchments with permeable soils, and (3) catchments with impermeable soils and surfaces (urban and suburban land uses). The literature suggests that natural flood management application is most effective for catchments <20 km2, reducing the likelihood of significant flood mitigation in large catchments. The relatively lower proportion of surface runoff and higher recharge in permeable catchments diminishes natural flood management’s likely efficacy. Impermeable catchments are most suited to natural flood management due to a wide variety of flow pathways, making the full suite of natural flood management interventions applicable. Detailed groundwater flood maps and hydrological models are required to identify catchments where NFM can be used in a targeted manner to de-synchronise sub-catchment flood waves or to intercept runoff generated via groundwater emergence. Whilst our analysis suggests that most chalk groundwater-dominated catchments in this sample are unlikely to benefit from significant flood reductions due to natural flood management, the positive impact on ecosystem services and biodiversity makes it an attractive proposition.

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