ENG09032 2019 Drainage Systems Design and Flood Management

Define, quantify and formulate the hydrological cycle, surface runoff, infiltration and rainfall/runoff correlation.

Carry out hydrological analysis using various techniques, predict maximum flood runoffs and design flows for natural channels, pipes and culverts. 

Appraise concepts of Sustainable Urban Drainage and apply to worked examples of source and site drainage controls. 

Critically evaluate concepts of groundwater flow, aquifers and groundwater contamination.

Interpret hydrological data and predict flood events

Design a sustainable drainage system

Estimate the hydraulic capacity of a culvert or bridge in a river channel

This module will be delivered using online lectures and workshops.

The students will be required to carry out a major project which will require the design of a sustainable surface water drainage system, inclusive of attenuation and treatment systems. The regional flood controls and prevention techniques used by the relevant government bodies in Ireland will also be examined by the incorporation of a preliminary flood risk assessment requirement in the project brief. 

The student will be required to carry out a project on the estimation of the hydraulic capacity of a bridge or culvert. This will include the estimation of 100 year year flood event with allowance for climate change and the prediction of flood levels corresponding to this event using a 1-D hydraulic model.

Final Exam

The repeat assessment for  this module will involve resubmission of failed projects and the sitting of the final written examination.

1. Hydrological Cycle, infiltration, surface runoff, catchment characteristics, rainfall data collection and  correlation, extreme rainfall events in Ireland, sources of flooding, soil moisture deficit. Rainfall hyetographs, runoff hydrographs, catchment characteristics, unit hydrographs, synthetic hydrographs. Available hydrometric and hydrological data and where to access it.

2. Energy and Continuity equations. Steady uniform flow, steady non uniform flow, unsteady flow. The Manning equation and its limitations. Normal depth of flow. Runoff estimation for surface water design. Design rainfall intensities Department of the Environment and Local Government, National Roads Authority, UK Standing Technical Committee for Sewers and Watermains Modified Rational Method. Greenfield runoff in larger catchments. Institute of Hydrology 124, Flood Study Report 1975, Flood Estimate Handbook,  Flood Study Update 2013, Growth curves for Irish conditions and their estimation. The Wallingford procedure and flood study report method for expanding rainfall data relating to flood events for estimating runoff and attenuation volumes . Worked pipeline design examples to various standards of pipelines and attenuation storage volumes. 

3.  Sustainable Drainage Design (SuDS). Definition and objective of SuDS.  Pollutants associated with runoff. Aquifers and groundwater pollution and recharge. Definition of regional local and poor aquifers. Geological Survey of Ireland (GSI). Turlough and karst limestone aquifers.  SuDS components, features of pretreatment, gullies, silt traps , soak pits, petrol interceptors. Site investigation and testing for percolation proprieties and groundwater. Source control techniques in SuDS. Dry swale, wet swale, grass channels. Swale design examples. Filter drains, fin drains, over the edge drainage.  Bio-retention basins, permeable pavements. Site control in SuDS, attenuation ponds, detention ponds, in line and off line infiltration basins, geo-cellular attenuation systems, attenuation tanks. Wetlands, linear wetlands,  retention times in constructed wetlands. Hybrid ponds. Accidental spill and its analyses in SuDS systems. Flow control methods, orifice flow, Venturi flume, weirs, vortex flow control. SuDS case study. 

4.Flood Study Report, Flood Estimation Handbook, IH 124, Introduction to the Flood Study Update (FSU),  Depth Duration Frequency Rainfall Models, Physical Catchment Descriptors (PCDS), Estimation of Q(med) and Q(medrural), gauged and un-gauged catchments, pivotal sites v's subject sites, Euclidean Pooling, Geographical Pooling, Growth Curve Prediction, Generalised Extreme Value (GEV), Log-normal Distribution , Generalised Logistical Distribution, Gumble Extreme Value Distribution. Hydrograph analyses and development for gauged and un-gauged catchments.  Interactive Bridge Invoking and Design Event Method (IBIDEM).

5.The development of flood policy in Ireland. Flood risk appraisal, Catchment Flood Risk Assessment and Management (CFRAMS), preliminary flood risk assessment maps, AFA flood hazard maps, Flood Risk Management Plans (FRMP's), National Flood Database. The planning system and flood risk management. The sequential approach and justification test. The definition of flood zones. Pluvial, fluvial, coastal, and groundwater  flooding. Highly vulnerable, less vulnerable and water compatible developments. Strategic Flood Risk Assessments (SFRA) and local authorities. Site Specific Flood Risk Assessment (SSFRA). SSFRA Screening and scoping process.  Mitigation measures and flood protection. Climate change prediction , definition of Mid Range Future Scenario (MRFS) and High End Future Scenario Events (HEFS).  

6.Irish Coastal Protection Strategy Study (ICPSS). Identification of coastal risks, coastal erosions, wave overtopping, tidal flooding. Prediction of extreme tidal events, coastal mapping. Tidal gauge network. Development of and accuracy of erosion and flood prediction mapping. Irish Sea Tidal and Coastal Surge Model (ISTCSM). Coastal protection techniques.

7. Hydraulic modelling techniques. 1-Dimensional Hydraulic Modelling, limitation of 1-D hydraulic modelling. 2-Dimensional hydraulic modelling, examples of 2-D hydraulic models, Light  Detection and Imaging Radar (LiDAR), Digital Terrain Models (DTM), Digital Surface Models (DSM),  linked 1-D and 2-D hydraulic models. The limitation of 2-D hydraulic modelling. 3-Dimensional hydraulic models and their applications. 

8.The Office of Public Works and its role in flood prevention. Section 50 applications, definition of hydraulic characteristics under section 50 applications. Hydraulic design requirements and level of technical analysis required under section 50 applications.  Efficient and inefficient elements in the hydraulic design of bridges and culverts. Worked examples on section 50 applications.