“integration of river, surface and sewer flow models: a ... underhill.pdf · “integration of...
TRANSCRIPT
1
Wallingford Software Limited
1
““Integration of river, surface and Integration of river, surface and sewer flow models: a novel sewer flow models: a novel
approach to flood risk modelling, approach to flood risk modelling, designed to meet the specific designed to meet the specific
needs of theneeds of the Floods and Water Floods and Water BillBill””
Claire UnderhillClaire Underhill
Legislation
Flooding in 2007Pitt Report 2008 Recommendation 18“Local Surface Water Management Plans, as set out under PPS25 andcoordinated by local authorities, should provide the basis for managingall local flood risk.”
Flood and Water Bill (April 2010)
2
Wallingford Software Limited
2
SWMPProblems of the future
New DevelopmentsUp to 3 million new homes will be built in England by 2016
Climate ChangeIncrease winter rainfall by 10 – 30% by the 2080s and rainfall intensity could increase by up to 20%.Urban CreepIn London alone, around two thirds of front gardens (equivalent to 22 times the size of Hyde Park) are already partially paved over to provide off-street parking.
(Making Space for WaterUrban flood risk & integrated drainage(HA2)
Types of FloodingSurface Water Runoff (pluvial):Runoff from high intensity rainfall – before reaches underground drainage system or watercourse
Groundwater Flooding;All water below ground surface and in direct contact with ground or subsoil
Sewer Flooding;Capacity is exceeded due to heavy rainfall.Flooding inside and outside buildings
Open Channel and Culverts;Receive most flow from inside urban area also interaction with larger watercourses
Overland Flows entering built up areas from fringe, also from groundwater sources
3
Wallingford Software Limited
3
Software PackagesTraditionally:
Collection Systems (InfoWorks CS)
River Systems (InfoWorks RS)
•Two separate packages!•Exchange of results through Open MI
Software Packages
InfoWorks CS (Collection Systems)Great for modelling closed pipe systems
4
Wallingford Software Limited
4
InfoWorks CS
How are river sections modelled?
Prismatic – No change in X sectionBetween upstream and downstream.
InfoWorks RS
InfoWorks RS (River Systems)Good for modelling open watercourses
5
Wallingford Software Limited
5
InfoWorks RS
How are closed pipes modelled?Manholes are not directly modelled
Not so convenient for pipe shape changes
Modelling 2D Flow Routing
The MeshIn InfoWorks CSIn InfoWorks RS
6
Wallingford Software Limited
6
The Mesh
IWRSIWCS
Triangles are a horizontal plane with the elevation of the plane derived by averaging the level at each vertex
DTM
1D – 2D connection for IWCS
InfoWorks Collection SystemsMesh
The length of the weir is the circumference of the shaft.
1D / 2D is by a weir or h/q relationship.
7
Wallingford Software Limited
7
2D Flooding in CS
1D - 2D connection in RS
Bank levels dictate flow to 2D meshElement levels adjusted where > 1D
Z2D
Z1DZsp
2D zone1D Bank Levels
8
Wallingford Software Limited
8
2D flooding in RS
Integrated modelling
Pitt review
9
Wallingford Software Limited
9
Models in ICMIncorporates
• River Sections (non-prismatic)
• Underground Pipes
• Culverts
• Bridges
• Controls (orifices,flap valves etc)
•SuDS features
2D Modelling in ICM
2D flooding occurs at nodes
and banks
10
Wallingford Software Limited
10
ICM
Sewer Flooding;Capacity is exceeded due to heavy rainfall.Flooding inside and outside buildings
Open Channel and Culverts;Receive most flow from inside urban area also interaction with larger watercourses
Direct RainfallSurface Water Runoff (pluvial):Runoff from high intensity rainfall – before reaches underground drainage system or watercourseOverland Flows entering built up areas from fringe, also from groundwater sources
11
Wallingford Software Limited
11
Other 2D features
Dam Breach
Other 2D Features
Porous BuildingsWalls
12
Wallingford Software Limited
12
Summary
2007 floods provided a catalyst for Integrated Urban ModellingProvides a more holistic approach suitable for Surface Water Management Plans2D flood routing includes movement between 1D and 2D