Waterco - Flood Risk, Hydraulic Modelling and Hydrological Services

www.waterco.co.uk

Flood Risk, Hydraulic Modelling & Hydrological Services

Waterco Consultants | Specialists in Water, Drainage and Flood

Who We Are Waterco has a team of hydrologists and hydraulic modellers with a reputation for delivering a cost effective and efficient service. We have successfully developed strategic partnerships with a number of high profile key clients who require additional specialist support to their in-house resource. Using an integrated approach, and working closely as part of the client team, we offer a ‘value for money’ service that is based on quality output and timely delivery.

Waterco are committed to providing our clients with practical solutions which are compatible with their objectives and add value to their projects.

Our expertise also covers the following services:

Water - Security, Asset and Strategic Planning, Pipelines and Distribution Systems (including self-lay)

Drainage - Pre Planning Assessment and Strategies, SuDS, Sewerage and Sewage Treatment

Flood Risk - Risk and Consequences Assessments, Catchment Approaches to Flood Risk Management, GIS Mapping

Waterco Consultants | Specialists in Water, Drainage and Flood

What We Offer ● Hydrology Studies (FEH Statistical, ReFH) ● 1D and 2D Hydraulic Modelling ● Flood Risk Assessments ● Fluvial and Coastal Breach Assessments ● Hazard and Vulnerability Mapping ● Water Quality Modelling ● Natural Flood Risk Management ● Flood Mitigation Design and Advice ● Hydro-geological Assessments ● Surface Water / rainfall modelling ● Network Modelling ● Coastal / Offshore Modelling ● Reservoir Inundation Modelling ● GIS mapping

Waterco Consultants | Specialists in Water, Drainage and Flood

Our Capabilities Service

Capability

Method / Tools

Benefit

Hydrology Studies (FEH Statistical, ReFH)

FEH Hydrology calculations

ReFH, FEH-STAT, IOH124 FEH CDROM3 + WINFAP

Greater understanding of catchment(s) Catchment studies to reduce flood risk Estimating extreme flows (to be used in the hydraulic models)

Fluvial (River) and Coastal Modelling

1D & 2D River Modelling Flood Alleviation Design

ISIS + TUFLOW, MIKE 11, MIKE 21, Site Surveys

Ability to assess and inform design on flood risk mitigation measures for developments, and critical assets exposured to flood risk.

Breach Assessments

2D Coastal Breach Analysis 2D flood defences breach analysis

TUFLOW, MIKE 21

Flood Risk/Consequences Assessment Assessment of failure of flood defence structures Flood resilience planning

Catchment Modelling

Integrated modelling of groundwater, surface water, recharge and evapotranspiration

MIKESHE

Strategic Planning Implementation of natural approaches Project scoping and option appraisal Supplementing/supporting funding applications

Hazard and Vulnerability Mapping

Flood Hazard mapping and MIKE 11, ISIS assessment of vulnerability MIKE 21, TUFLOW of infrastructure and assets Site Surveys

Assessment of vulnerability and resilience of infrastructure and assets to site specific flood hazard Inform validity of mitigation measures

Reservoir Inundation Modelling (RIM)

2D reservoir failure / dam break modelling

Preparation of reservoir inundation mapping and flood emergency plans to meet government standards. Flood Risk Assessment

Water Quality Modelling

Assessment of parameters MIKE 11, ISIS, MIKE 21 AD TUFLOW such as source, concentrations, transport and dispersion

To quantify, assess and appraise design and mitigation actions as well as demonstrate compliance with statutory regulations

Surface Water/Rainfall Modelling

1D & 2D Surface Water Modelling

MIKE 21 TUFLOW Site Surveys Client Liaison

Undertake strategic planning –Surface Water Management Plans Development drainage strategies Flood risk assessment design and mitigation

Network Modelling

Water supply network Sewerage and drainage network

Review and appraise existing networks InfoWorks CS, EPASWMM, MIKE URBAN, Design and evaluate new networks Integral part of asset surveys, revision EPANET of asset databases & information systems Investigative work associated with wet infrastructure.

Coastal and Offshore Modelling

Wave studies, sediment / morphological studies, water quality modelling

MIKE 21, TUFLOW

Assessments to support design Support/inform environmental impact assessments associated with coastal and offshore structures

Geographic Information Systems

Data management, geoprocessing and spatial analysis, flood mechanism animations, software development

ArcGIS, MapInfo, QGIS, Global Mapper, Visual Basic, Python, MapBasic

Correlation and presentation of data sets Effective tool in identifying and mapping project objectives, issues and opportunities Animating complex models for stakeholder education

TUFLOW, MIKE 21

Waterco Consultants | Specialists in Water, Drainage and Flood

Meet the Team Dr. Deepak Kharat B.E. M.Tech PhD MCIWEM CWEM CSci Technical Director Deepak has over 17 years' experience working within the wider field of Civil Engineering and particularly within the hydraulic modelling sector, including academia, commercial practice and government (with SEPA). His PhD studies focused on integrated 1D/2D modelling of urban floodplains using LiDAR data. In commercial practice, Deepak has delivered a variety of complex projects which included the 1D and 2D hydraulic modelling of Rivers and Canal Networks, Sewerage & Drainage Systems, Dam-Breaks, Levee Breaches and Water Supply Systems. Deepak has developed his appraisal skills over the years with detailed knowledge, balanced with practical applications. Within Waterco, Deepak takes the project lead on a diverse portfolio of complex modelling projects whilst providing the wider team with technical guidance and support.

Specialities: 1D, 2D and integrated 1D/2D modelling of rivers; urban sewerage & drainage systems; hydrological and hydraulic analysis; dambreak analysis; design of water resources related structures (e.g. dams and canals); GIS and remote sensing; Flood Risk Assessments; Water Resources Management; Training Programs and Project Management.

Chris Lewis MEng (Hons) Associate Civil Engineer - Hydraulics Chris leads Waterco’s hydraulic modelling team having joined the company in 2008 with a Masters degree in Civil Engineering from the University of Warwick. As well as providing the strategic direction for the team, Chris specialises in detailed flood risk assessment and hydrodynamic modelling for the construction, utilities and energy sectors. Using his substantial experience in 1D/2D hydraulic modelling, he provides clients with a detailed understanding of the flood risks associated with their schemes and provides practical advice on the various options available to mitigate risk and maximise potential. Chris has project managed over 100 hydraulic modelling projects and is proficient in a variety of software packages including ISIS, TUFLOW, MIKE11/21/Flood and HEC-RAS. Specialties: Detailed 1D/2D Hydraulic Modelling (MIKE11/21, ISIS, Tuflow, HEC-RAS); Flood Risk Assessments (NPPF/TAN15); Breach Assessments; Coastal Modelling; Flood Hazard Ratings (FD2320); Structural Design Calculations; Drainage and SuDS Design (MicroDrainage, WinDes); Compensatory Storage; Flood Zone Reclassification

Waterco Consultants | Specialists in Water, Drainage and Flood

Aled Williams Bsc (Hons) Flood Risk Assessment Manager Aled, with a degree in Geography is a member of the flood risk team. He is responsible for Environmental Reports including: Flood Risk Assessments; Code for Sustainable Homes (CSH) Sur1 and Sur 2; Surface Water Run-Off Calculations, Flood Response and Evacuation Plans. Drawing on his experience in report writing across these subjects, Aled is able to advise and guide clients not only through the maze of legislation and statutory requirements, he makes sure that design recommendations are compliant but also practical and cost effective ensuring a coherent combined strategy for flood risk and drainage.

Specialties: Development site appraisal – Flood Risk and Drainage; Drainage Strategy Planning; Drainage Design; Flood Risk Assessment/ Flood Consequences Assessment; Code for Sustainable Homes-Sur 1 and Sur 2; Surface Water Run-Off Calculations; Asset security

Stephen Conway BSc (Hons) Principal Hydrologist Steve obtained a first class honours degree in Physics and fluid mechanics, and this in depth knowledge of statistics and mathematics provides a solid basis for hydrological assessment. This is further evidenced by his thorough knowledge of the Flood Estimation Handbook and the associated research and background papers. Steve has a particular interest in the hydrology of small catchments, including their geomorphology, geological and botanical characteristics.

Specialties: Asset security; scientific research; emergency planning; Flood Risk Assessments/Flood Consequence Assessments (NPPF/TAN15); Flood probability statistics; catchment run off assessments

Geoff Anderton IEng CIWEM MICE MCIWEM Hydraulics and Hydrology Consultant Geoff brings over 40 years of engineering design experience to support the modelling team with expert knowledge in the hydraulic design of pipelines, channels and water control structures. He has been involved in the design and site supervision of major infrastructure and drainage contracts and has extensive experience in water industry requirements, including investigating and developing solutions for surface water and Combined Sewer Overflow (CSO) and Unsatisfactory Intermittent Discharge (UID) problems.

Geoff also has expert knowledge in Hydrology.

Specialties: Detailed design for sewerage and sewage treatment; hydraulic design; pipeline hydraulics; sewerage treatment process design; foul and surface water sewer system design; CSO; Unsatisfactory Intermittent Discharge (UID); hydrology; flood alleviation design; Flood Risk Assessments/ Flood Consequence Assessments (NPPF/TAN15)

Waterco Consultants | Specialists in Water, Drainage and Flood

David Hughes MEng (Hons) Hydraulic Modeller David graduated from the University of Southampton with a Masters in Civil Engineering in 2010. He has considerable experience of ISIS and ESTRYTUFLOW modelling having completed over 30 modelling projects providing clients with a detailed understanding of flood risk and hazards. He has recently completed a Surface Water Management Plan model, strategically highlighting the surface water flooding hotspots for further study. He has also worked on several large GIS-based projects being responsible for efficient data management. Outside of work, David enjoys kayaking and taking part in white water rafting competitions.

Specialties: Detailed 1D/2D Hydraulic Modelling (ISIS, ESTRY, TUFLOW, MIKE11/21/FLOOD; HEC-RAS); SMS 11; Breach Analysis; Flood Hazard Mapping; Surface Water Management Plans; Direct Rainfall Modelling; AutoCAD; GIS (ArcGIS, MapInfo, Quantum GIS); Visual Basic programming; MapBasic

Bethan Young BSc (Hons) Hydraulic Modeller Bethan studied for her degree (BSc in Environmental Earth Science) at Aberystwyth University and is a key member of the hydraulic modelling team. She works on projects including 1D/2D hydraulic models (using MIKEFLOOD) and Hydrology Assessments (using FEH and ReFH). She has had experience in both network modelling and coastal inundation/breach modelling. She is also experienced in flood risk assessments and has been involved in many schemes in Wales-making the most of her Welsh speaking. Recently Bethan has become a graduate member of CIWEM and has begun her journey to becoming chartered.

Specialties: Hydraulic Modelling, FEH, ReFH, GIS; Engineering Geology (rock, soil and water); hydrochemistry; Flood Risk Assessments/ Flood Consequence Assessments (NPPF/TAN15)

Sandeep Bomminayuni Msc Hydraulic/Coastal Modeller Sandeep joined Waterco in April to lead on coastal, offshore, water quality and geomorphological modelling. Sandeep is poised to complete his PhD degree at Cardiff University and holds Master's degree in Civil Engineering from Georgia Institute of Technology, USA and Bachelor's degree in Civil Engineering from Indian Institute of Technology. Sandeep has built up his hydraulic modelling expertise through diverse projects related to coastal and inland flooding, sediment and pollutant transport, marine renewable energy and bathing water quality compliance. He also has published papers in scientific journals and presented in seminars and conferences.

Specialities: Hydraulic modelling; Flood risk assessment; Hydro-informatics; Coastal modelling; Bathing water quality compliance; Renewable energy; High-performance computing.

Waterco Consultants | Specialists in Water, Drainage and Flood

Karen Pinkerton Bsc (Hons) KTP Research Associate Karen is an experienced GIS Analyst, who is currently the Research Associate on the Natural Flood Management (NFM) Knowledge Transfer Partnership with the University of Liverpool. Drawing on her skills in flood management and GIS mapping, Karen is developing a number of pilot projects with local authorities and numerous stakeholders, to identify flood mitigation projects which provide multiple benefits by utilising NFM approaches. Working with our Geographers, Hydrologists, and Hydraulic Modellers together with a team of academics from the University of Liverpool, Karen will lead the multi-disciplined team in the development of this approach.

Specialties: GIS Software (ArcGIS, QGIS, MapInfo); Hydrology; Emergency Planning; Flood Resilience; Stakeholder management

Manfredi Toraldo BA, MSc Env, MSc Hydroinformatics Hydraulic Engineer and Hydrologist Manfredi works in the Natural Flood Management team, an experienced hydrologist, hydraulic modeller and engineer. He applies this experience and understanding of the hydrology of catchments to model natural interventions both within the rural and urban setting to mitigate flood risk.

Manfredi also works with the Hydraulic modelling team on a variety of development and regeneration projects.

Specialties: Detailed 1D/2D Hydraulic Modelling; AutoCAD; GIS; Hydrological Assessments; Engineering design; Site engineering; Water supply design

Laura Anderton Hydrologist and Data Management Laura is a key member of the Flood Risk Management team and has developed her technical skills and logical approach through work on data management projects. These have involved liaison with multiple contacts to collect information from a variety of sources. Whilst at Waterco, she has gained a detailed understanding of hydrological processes and has been trained in the FEH statistical and ReFH methods. Laura is currently involved in a Knowledge Transfer Partnership project, working with Aberystwyth University, using remote sensing and sourcing hydrological data sets for use with hydraulic models. She also continues to provide general IT support throughout the business and maintains the company database management systems.

Specialties: FEH statistical and ReFH methods; WINFAP-FEH, FEH-CD ROM 3 and Global Mapper software; Hydrology Assessments; remote sensing; GIS; IT support; web programming; graphic design software packages; data acquisition and management using Filemaker, Excel and Access, SQL; project coordination

Waterco Consultants | Specialists in Water, Drainage and Flood

Angharad Llewelyn MSc Flood Risk Assessor Angharad, with a masters degree in Environmental Dynamics and Climate Change is a member of the flood risk team. She is responsible for Environmental Reports including: Flood Risk and Consequences Assessments; Code for Sustainable Homes (CSH) Sur1 and Sur 2; and Surface Water Runoff Calculations. Angharad is able to advise and guide clients not only through the maze of legislation and statutory requirements, she makes sure that design recommendations are compliant but also practical and cost effective ensuring a coherent combined strategy for flood risk and drainage Specialties: Code for Sustainable Homes-Sur 1 and Sur 2; Surface Water Run-Off Calculations; Flood Risk and Consequences Assessments

Jordan Jones BSc Flood Risk Assessor Jordan, with a degree in Environmental Science is a member of the flood risk team. She is responsible for Environmental Reports including: Flood Risk and Consequences Assessments; Code for Sustainable Homes (CSH) Sur1 and Sur 2; and Surface Water Runoff Calculations. Jordan is able to advise and guide clients not only through the maze of legislation and statutory requirements, she makes sure that design recommendations are compliant but also practical and cost effective ensuring a coherent combined strategy for flood risk and drainage.

Specialties: Code for Sustainable Homes-Sur 1 and Sur 2; Surface Water Run-Off Calculations; Flood Risk and Consequences Assessments

Ruari Benton Bsc (Hons) Flood Risk Assessor Ruari graduated with an honours degree from Lancaster University in 2012, where he gained experience in report writing and analysing data.

After working abroad for a year, following university, he became enthusiastic to work in the environmental sector. He joined the flood risk team at Waterco in 2014. He is responsible for Environmental Reports including: Flood Risk and Consequences Assessments; Code for Sustainable Homes (CSH) Sur1 and Sur 2 and Surface Water Runoff Calculations.

Specialties: Code for Sustainable Homes-Sur 1 and Sur 2; Surface Water Run-Off Calculations; Flood Risk and Consequences Assessments; client liaison

Waterco team CVs are available on request at enquiries@waterco.co.uk.

Waterco Consultants | Specialists in Water, Drainage and Flood

Case Study Hydrology Assessment Assessment of peak flows during a range of extreme events using FEH methods

Ogwr Fach, Bridgend Services Provided Ÿ Detailed hydrology calculations using FEH (i.e. FEH Statistical & ReFH) Ÿ WINFAP-FEH 3 Ÿ FEH CD-ROM 3 Ÿ ReFH Spreadsheet Ÿ EA Calculation Record Ÿ EA Checklist Ÿ Pooling group review Ÿ Climate Change

Strategy In order to calculate the predicted flows generated by the Ogwr Fach catchment during an extreme event, a hydrology assessment was carried out.

A review of the Ogwr Fach’s catchment descriptors was carried out to review reservoir influence, urban extent, rainfall, soil types and catchment permeability.

Using both the Revitalised Flood Hydrograph (ReFH) and the FEH Statistical methods, detailed hydrology calculations were completed to calculate predicted peak flows for the 1% AEP and 0.1% AEP fluvial events.

Scheme Waterco was instructed to carry out detailed hydrology calculations to determine peak flows in the Ogwr Fach watercourse. A tributary of the Afon Ogmore, the Ogwr Fach passes through Blackmill, Bridgend, Mid Glamorgan and North Wales.

The purpose of the study was to provide peaks flows and hydrographs for a range of extreme fluvial events, to be used as inputs for a hydraulic model produced by C D Gray & Associates. Peak flows had previously been calculated in 2006, however the EA requested these be updated.

The updated peak flows were calculated in accordance with current Environment Agency (EA) guidelines, which includes accounting for the impacts of climate change.

Outcomes and Solutions The final flood estimation method chosen was the Adjusted Statistical method. The ReFH hydrographs were scaled to the Adjusted Statistical peaks and the final hydrographs issued to C D Gray & Associates.

C D Gray & Associates inputted these hydrographs into a 1D hydraulic model (HEC-RAS) of the Ogwr Fach watercourse.

For more information on our hydrology assessment capabilities please visit our web site or contact us using the details below.

FEH guidance stresses the uncertainty of the FEH Statistical 0.1% peak flow.

As such the 1% Statistical peak flow was multiplied by the ratio of the 0.1% and 1% ReFH flows (referred to as the Adjusted Statistical method).

01824 702220 - www.waterco.co.uk - enquiries@waterco.co.uk Waterco Ltd. Eden Court, Lon Parcwr Business Park, Ruthin, Denbighshire, LL15 1NJ

Case Study Hydraulic Modelling Flood Consequences and Solution Assessment for extreme floods

Pontsticill Water Treatment Works Services Provided

Scheme

Ÿ Flow assessment from impounding reservoir Ÿ Integrated 1D and 2D hydraulic model Ÿ Investigation of previous flood events Ÿ Fluvial and overland flooding Ÿ Flood extents, depths and velocities Ÿ Modelling of solution options Ÿ Flood protection measures

Waterco were instructed by Dŵr Cymru Welsh Water to update existing flood risk information to determine the areas of the site at risk from a 1% AEP event, including allowance for climate change. Our brief also included an assessment of options to protect the site against the identified risk. Dŵr Cymru Welsh Water accepted the proposed solutions and extended our brief to include the preparation of the design package.

Strategy A hydrology assessment was completed for the catchment and the impounding reservoir spillway. This used the revitalised FSR/FEH rainfallrunoff method and catchment descriptor information from the latest software. The attenuation effect of the reservoir on the peak inflows was calculated to create an outflow hydrograph for the 2%, 1% and 1% with climate change events.

A 1D river network model of the Taf Fechan river including weir and bridge structures was linked to a detailed 2D spatial model developed from LiDAR data and site specific level data.

Overland flow was also modelled using the 2D spatial model.

Detailed analysis of the results predicted flood depths, velocities and flow routes across the site. Solution options were also modelled. These included the erection of a flood wall, the removal of a bridge, removal of a weir and bypass of a weir. As well as estimating costs, the design, construction and operation of each option was considered.

Outcomes and Solutions In addition to the Flood Consequences Assessment Report, hydrology assessment and modelling report, we provided a cost benefit assessment of the solution options. Our recommended solution was to install a new river channel bypass to the gauging weir for use during high flows, raise one bank, and clear some vegetation to protect against fluvial flooding.

Other measures to protect against overland flow included protecting building thresholds and enlarging the flow route draining the site.

We arranged site surveys and completed the Planning and Flood Defence Consent applications, so the work could be completed as programmed.

The completed scheme provided passive flood protection and enhanced the biodiversity of the river habitat.

For more information please visit our web site or contact us.

01824 702220 - www.waterco.co.uk - enquiries@waterco.co.uk Waterco Ltd. Eden Court, Lon Parcwr Business Park, Ruthin, Denbighshire, LL15 1NJ

Case Study Hydraulic Modelling Flood Zone Reclassification

Cresswell, Staffordshire Services Provided

Scheme

Ÿ Integrated 1D and 2D hydraulic model Ÿ Flow assessment of rivers (FEH Statistical) Ÿ Extreme Flood Outlines, Depths & Velocities Ÿ Flow route determination Ÿ Hazard Mapping Ÿ Flood Zone Reclassification Ÿ Flood Mitigation Measures

Waterco were instructed to carry out detailed hydraulic modelling of the River Blithe near Cresswell. The results were used as supporting evidence in the Flood Risk Assessment being prepared for a planning application for a proposed biomass power plant. The client was SKM-Enviros.

Strategy The area was remodelled using an integrated 1D/2D hydraulic model developed using MIKEFLOOD, DHI’s advanced hydraulic modelling software application.

A 1D river network model of the River Cresswell and associated tributary was linked with a detailed spatial model of the floodplain, developed from high resolution LiDAR data and site levels.

Using a relatively fine grid resolution (2m²) for the Digital Elevation Model (DEM), a much improved representation of the floodplain was possible.

Using calculated and agreed fluvial event flows (FEH Statistical and ReFH) it was possible to more accurately quantify the risk and extent of potential flooding at the site. Both the 1% AEP and 0.1% AEP events were simulated, with allowances for climate change being included as appropriate.

The EA flood map for the area showed the site to be at widespread flood risk during extreme fluvial events. Following a review of the existing modelled data at the site it was thought that a better understanding of the flood risk posed to the site could be achieved through the use of more accurate data and techniques.

In addition to demonstrating reduced flood risk, a more accurate representation of the floodplain would help inform final design layouts and any required flood mitigation measures.

Outcomes and Solutions The simulation results were subject to detailed analysis with predicted flood depth, velocities and flow routes being determined. This information was then used in conjunction with DEFRA guidance note ‘Flood Risks to People’ to produce a hazard map and further evaluate the impact of flooding on the proposed development and the surroundings.

It was demonstrated that the current EA flood map for the area is overly conservative and that much of the site was in fact flood free during 0.1% AEP fluvial event.

Our model successfully demonstrated that the flood zone should be reclassified and the results will be used by the EA to update the EA flood map for the area.

For more information on our hydraulic modelling capabilities please visit our web site or contact us.

01824 702220 - www.waterco.co.uk - enquiries@waterco.co.uk Waterco Ltd. Eden Court, Lon Parcwr Business Park, Ruthin, Denbighshire, LL15 1NJ

Case Study Breach Assessment Assessment of flood risk posed to site from possible breach of coastal defences

Immingham, South Humberside Services Provided

Scheme

Ÿ Ÿ Ÿ Ÿ Ÿ Ÿ

Waterco were instructed to produce a series of breach assessment

Modelling breach of coastal defence Extreme Flood Outlines Hazard Mapping Advising on Solutions Liaison with the EA Hydraulic Modelling Report

Strategy After an initial review of the scheme, the local Environment Agency office was contacted to discuss any specific modelling requirements and hydrodynamic parameters to be applied. Early involvement with the EA and other outside agencies proved invaluable and enabled the acceleration of the scheme’s progress, ultimately leading to client savings.

A Digital Elevation Model (DEM) of the area was created using high resolution LiDAR data. Detailed level information of any important local features e.g. the coastal defences were added for refinement.

The 2D models, created in MIKE 21 from DHI, used this DEM to simulate the overland flow resulting from a breach in the defences under a series of predicted tidal cycles. The effects of climate change were also taken into account.

This information was then used in conjunction with DEFRA guidance note ‘Flood Risks to People’ to produce a hazard map to further evaluate the impact of such a failure on the proposed developments and their surroundings.

models for a proposed large scale commercial scheme to the north of Immingham Dock, South Humberside. By simulating a possible breach in the local Humber Estuary coastal defences the hazards and risks posed to the site could be quantified and the results incorporated in a Flood Risk Assessment as part of the planning process.

Outcomes and Solutions The breach modelling quantified the flood risk to the site by predicting flood levels, depths, rate of rise and speed of onset.

This information was then used to: ·

inform the Flood Risk Assessment

·

produce a hazard map to further evaluate the impact of such a failure on the proposed developments and the surroundings (in conjunction with DEFRA guidance note ‘Flood Risks to People’).

In addition to producing a full modelling report, we used the powerful results visualisation tools of DHI to produce a series of animations and flood outline maps. Provided on DVD, these results presentations are an excellent way of illustrating the flood risk, and are a foundation on which mitigation measures can be appraised.

For more information on our hydraulic modelling capabilities please visit our web site or contact us.

01824 702220 - www.waterco.co.uk - enquiries@waterco.co.uk Waterco Ltd. Eden Court, Lon Parcwr Business Park, Ruthin, Denbighshire, LL15 1NJ

Case Study Flood Risk Analysis of Critical Infrastructure Detailed hydraulic modelling and flood risk assessment at 20 electricity substations

England Services Provided Ÿ Integrated 1D/2D hydraulic modelling Ÿ 2D Breach/overtopping analysis Ÿ Hydrology review and calculations (FEH Statistical, ReFH) Ÿ Extreme Flood Outlines, Depths & Velocities Ÿ Flow route analysis Ÿ Hazard Mapping Ÿ Flood Mitigation Measures

Scheme Framework consultants WYG Engineering, engaged Waterco to undertake the detailed hydraulic modelling and flood risk assessments for 20 critical electricity substation sites. This was part of a major Network Resilience Strategy to assess flood risk at existing substations; establish the current standard of flood protection; and determine any requirement for flood protection works.

The geographical variation of the assets called for a number of different modelling approaches to be used, with sites requiring an assessment of fluvial and/or tidal flood risk. These included integrated 1D/2D fluvial models and 2D tidal breach models. The choice of software used (ISIS-TuFLOW, MIKE 11/21) was determined by the availability of existing models and the specific output requirements for each site.

Strategy 1D/2D Hydraulic Models 1D river network model of the rivers and any associated tributaries developed from existing EA model data or surveyed river section data. Generally inflow hydrology was taken from the existing EA 1D models.

Once verified, the 1D model linked to a detailed 2D Digital Terrain Model (DTM) of the potential floodplain, developed from high resolution LiDAR data and site specific level data.

2D Breach Models DTM of predicted floodplain including local flood defences based on LiDAR data and EA flood defence inspection reports.

Breach in defence then added (generally 40m wide) at worst case location for site (generally closest).

Head-Time inflow boundary was extracted from existing EA models and applied through breach.

Substation Type

Return Period Fluvial Tidal

GSP

1% AEP 0.1% AEP

0.5% AEP

BSP

1% AEP 0.1% AEP

0.5% AEP

Primary

0.1% AEP

0.5% AEP

The fluvial return period requirement for each asset was dependent on the type of substation being considered. The larger substations (GSP and BSP) required an assessment of the 0.1% AEP event (1 in 1000) in addition to the the 1% AEP event (1 in 100). Primary substations required an assessment of the 1% AEP fluvial event only.

Outcomes and Solutions Results data and statistics extracted from each simulation provided detailed information of the predicted flood levels, depths and rate of raise at each substation. Generally the flood mapping produced by this study showed the current Environment Agency (EA) flood maps to be conservative; particularly during the breach scenarios.

Using these results the current Standard of Protection (SOP) was established at each site. Where the SOP was shown to be less than the required level, mitigation options (e.g. flood walls, lifting of critical equipment etc) were proposed.

01824 702220 - www.waterco.co.uk - enquiries@waterco.co.uk Waterco Ltd. Eden Court, Lon Parcwr Business Park, Ruthin, Denbighshire, LL15 1NJ

Case Study Hydraulic Modelling Detailed hydraulic model enabling reclassification of flood zone

Hailes, Gloucestershire Services Provided

Scheme

Ÿ Integrated 1D and 2D hydraulic model Ÿ Flow assessment of river (FEH Statistical) Ÿ Flood Zone Reclassification Ÿ Extreme Flood Outlines, Depths & Velocities Ÿ Flow route determination Ÿ Hazard Mapping

Waterco was commissioned to undertake hydraulic river modelling to support a Flood Risk Assessment for a proposed residential development near Hailes, Gloucestershire. The site was shown on the Environment Agency (EA) flood map to be at risk of flooding during a 1 in 200 year event and there was therefore an objection to the development. Modelling was undertaken to provide better detail than the EA flood map, and to establish whether the flood zone could be reclassified and the objection legitimately removed.

Strategy

Outcomes and Solutions

The existing EA hydraulic modelling was based on a relatively coarse grid resolution and did not account for local topographical features and structures.

To improve the resolution and accuracy of the model a detailed 1D river network model was joined to a 2D Digital Elevation Model (DEM).

All simulations demonstrated that the site was not at risk of flooding from the events considered. Predicted flood depths, velocities and flow routes were extracted and a hazard map produced.

As agreed with the local EA office, the predicted peak flows and hydrographs were calculated using FEH Rainfall Run-off Method (ReFH spreadsheet).

Climate change was also taken into account.

The 1D river network, prepared in MIKE 11, simulated the small watercourse running past the site in addition to a number of existing culverts and partial blockages.

This 1D river model was then linked to a 2D DEM developed from LiDAR data and site specific level data. The 1% AEP and 0.1% AEP events were considered.

The results demonstrated that the site should be reclassified as Flood Zone 1. The model/report was submitted to the EA to enable them to update their flood maps.

The report was accepted by the EA with the Flood Zone being reclassified to zone 1.

In addition to producing a full modelling report, we used the powerful results visualisation tools of DHI to produce a series of animations and flood outline maps. Provided on DVD, these results presentations are an excellent way of illustrating the flood risk to the project design team and stakeholders.

For more information on our hydraulic modelling capabilities please visit our web site or contact us at enquiries@waterco.co.uk.

01824 702220 - www.waterco.co.uk - enquiries@waterco.co.uk Waterco Ltd. Eden Court, Lon Parcwr Business Park, Ruthin, Denbighshire, LL15 1NJ

Capability Statement Coastal Water Quality Assessment

Pollution sources: ● Point sources – rivers, streams, drainage outlets, effluent outfalls ● Diffuse sources – overland flow, agricultural runoff

Waterco have the Modelling expertise and experience to carry out Water Quality Assessments for coastal areas to ensure compliance with European Union Directives. We identify and characterise pollution sources entering coastal waters and model their impact on the surrounding areas.

Our services include: ● Coastal water quality modelling ● Environmental impact assessment

Impacts of pollution: ● Endangers aquatic life ● Disrupts ecosystem

● Regulatory compliance ● Integrated catchment to coast modelling ● Asset management solutions

● Poses risk to public health

Guidelines: ● EU Bathing Waters Directive (2006/7/EC) ● EU Shellfish Waters Directive (2006/113/EC) ● EU Water Framework Directive (2000/60/EC)

Bathing water compliance study for Swansea Bay, UK [Bomminayuni, S., PhD thesis (unpublished), Cardiff University]

01824 702220 - www.waterco.co.uk - enquiries@waterco.co.uk Waterco Ltd. Eden Court, Lon Parcwr Business Park, Ruthin, Denbighshire, LL15 1NJ

Capability Statement Coastal Sediment Transport & Morphology Assessment

Agents of coastal sediment transport: ● Wind waves

Waterco have the Modelling expertise and experience to carry out Sediment transport and Morphology Assessments for coastal areas.

We identify and model the governing coastal processes to understand their influence on shoreline evolution.

● Sea currents

Our services include: ● Tides and storm surges ● Wave and sediment transport modelling

Impacts of morphological changes:

● Understanding coastal processes and shoreline evolution ● Coastal erosion and beach protection ● Managing navigable channels

● Loss of economy, enhanced flood risk

● Evaluating scour around coastal structures

● Ecosystem and environmental impacts ● Damage to infrastructure

Guidelines: ● Shoreline Management Plans ● National Flood and Coastal Erosion Risk Management

01824 702220 - www.waterco.co.uk - enquiries@waterco.co.uk Waterco Ltd. Eden Court, Lon Parcwr Business Park, Ruthin, Denbighshire, LL15 1NJ

Capability Statement Tidal Renewable Energy Resource Assessment

Tidal energy potential in the UK: ● 25 to 30 GW of tidal range potential - 12% of UK electricity demand ● 30 to 50 GW of wave and tidal stream energy potential 20% of UK electricity demand

Key considerations: ● Physical characteristics of sites: water depth, tidal range, current speeds etc. ● Ecosystem and environmental impacts ● Socioeconomic constraints

Our services include: ● Coastal modelling

Tidal Barrage: ● Energy generation similar to hydro-electric dams

● Identification and characterisation of potential sites ● Estimation of available tidal renewable energy ● Feasibility and environmental impact assessment studies

● Depends on tidal range and volume of water impounded

Tidal stream energy: ● Energy generation similar to wind turbines ● Depends on current speed and turbine swept area

01824 702220 - www.waterco.co.uk - enquiries@waterco.co.uk Waterco Ltd. Eden Court, Lon Parcwr Business Park, Ruthin, Denbighshire, LL15 1NJ

Capability Statement Scour Assessment for Hydraulic Structures

Scour mechanisms: ·

Contraction scour – live bed and clear water scour

·

Assessments of existing structures are required to determine whether: ·

Structures are at risk of collapse

Local scour – bridge piers

·

Measures are required to reduce risk from scour

and abutments

·

Replacement or substantial rehabilitation would be required

Key parameters: ·

Current speeds at upstream and bridge section

· ·

Bed sediment characteristics Geometrical dimensions of

Our services include: ·

Site investigation

·

Hydrology and Geomorphological assessments

·

Hydraulic and sediment transport modelling

·

Scour risk assessment based on FHWA and DMRB guidelines

the bridge structure

Guidelines: ·

HEC-18 report of the US Federal Hghway Administration (FHWA, 2012)

·

UK Design Manual for Roads and Bridges (DMRB, 2012) Bridge scour analysis (Hydraulic toolbox, FHWA)

01824 702220 - www.waterco.co.uk - enquiries@waterco.co.uk Waterco Ltd. Eden Court, Lon Parcwr Business Park, Ruthin, Denbighshire, LL15 1NJ

Capability Statement Design Assessment of Culvert Trash & Security Screens

Key Considerations:

Design Guides: ● Culvert Design and Operation Guide (CIRIA, 2010) ● Trash and Security Screen Guide (EA, 2009)

Assessments of existing assets may be required to determine whether: ● Performance of the assets meets

the

current

● Legislative and environmental requirements ● Potential debris load and debris characteristics ● Screen area, bar spacing, screen angle, screen alignment, screen height and stages ● Hydrological, geo-morphological and hydraulic analysis including flood risk due to blockages ● Operation, inspection and maintenance issues ● Overtopping flood route and screen bypass ● Monitoring systems (telemetry and CCTV) ● Environmental consequences & opportunities ● Visual amenity issues ● Health & Safety issues ● Lighting issues

policy,

operational requirements and performance specifications ● Original design standards are still relevant ● Asset is operating at an optimum performance level

Our services include: ● Design ● Assessment ● Training

01824 702220 - www.waterco.co.uk - enquiries@waterco.co.uk Waterco Ltd. Eden Court, Lon Parcwr Business Park, Ruthin, Denbighshire, LL15 1NJ

Waterco Consultants | Specialists in Water, Drainage and Flood (+44) 1824 702220 www.waterco.co.uk enquiries@waterco.co.uk

Waterco Ltd. Lon Parcwr Business Park Ruthin Denbighshire LL15 1NJ