|
|
| (204 intermediate revisions by 12 users not shown) |
| Line 1: |
Line 1: |
| {{learned|what the rainfall overlay is|how the rainfall overlay can be used|how the rainfall overlay can be configured|what principles govern its calculation|what formulas are used to perform the calculations}}
| | [[File:Rainfall-Overlay.jpg|thumb|right|200px|Rainfall overlay]] |
| | The Rainfall Overlay is a variant of the [[Water Overlay]], which in turn is a [[Grid overlay|grid overlay]]. Water overlays are connected to the [[Water Module]], a complex hydrological calculation module within the {{software}}. |
|
| |
|
| ==The Rainfall Overlay==
| | The Rainfall overlay specializes in displaying the hazard and impact of (heavy) rainfall over the project area. Based on the elevation model, terrain roughness and representations of the sewer and water systems, several result types can be generated by the accompanying Water Module. |
| The rainfall overlay is a [[grid overlay]] showing results of heavy rainfall on the surface (inundation), sub-surface (groundwater), open water and sewer system. The following results are produced:
| |
| * '''BASE_GROUNDWATER_DISTANCE''': shows the distance between the groundwater level. For now, the height of the ground level is including the buildings and other objects on the ground (the height to the surface). This will be changed to the terrain height in a following release.
| |
| *'''BASE_TYPES''': shows the division of the grid cells in water, land or sewer areas that are connected to the sewer. Playing with the grid cell size, will make this division between areas/terrain types more or less accurate, which affects the calculation of the flooding.
| |
| *'''EVAPORATED''': shows how much water is evaporated after the rainfall in the defined simulation time. For more information on how this layer is calculated, see the [[Rainfall overlay calculations]] page.
| |
| *'''IMPACTED_BUILDINGS''': shows all constructions or neighboring cells which will be flooded with the settings as provided in the rain overlay wizard and the IMPACT_FLOOD_THRESHOLD_M attribute (see attributes of the rainfall overlay). The result type shows therefore which constructions or neighboring cells are more flooded than the defined threshold. The colors are based on the attribute 'Critical infrastructure' in the function values table, in where a classification is made in the importance of flooding of different types of buildings. Three values can be entered in the function values table: 0 (not very critical, for example a shed or a park), 1 (important, most buildings), 2 (critical, such as a hospital or a school).
| |
| *'''SEWER_LAST_VALUE''': The amount of water remaining in the sewer after the simulation is over
| |
| *'''SEWER_MAX_VALUE''': The largest amount of water that was in the sewer at any time during the simulation
| |
| *'''SURFACE_DURATION''': The total amount of time the surface has water on it
| |
| *'''SURFACE_FLOW''': The total amount of water which has flowed across the surface
| |
| *'''SURFACE_LAST_VALUE''': The amount of water remaining on the surface after the simulation is over
| |
| *'''SURFACE_MAX_VALUE''': The largest amount of water that was on the surface at any time during the simulation. Differs from WATER_STRESS in that water stored on bodies of water is always included.
| |
| *'''UNDERGROUND_FLOW''': The total amount of water which has flowed underground
| |
| *'''UNDERGROUND_LAST_VALUE''': the amount of water which has flowed underground after the rain simulation is over.
| |
| *'''UNDERGROUND_MAX_VALUE''': the largest amount of water that flowed underground at any time during the simulation
| |
| *'''WATER_STRESS''': The maximum amount of excess water at any time during the simulation. Differs from SURFACE_MAX_VALUE because water stored on bodies of water are not immediately deemed "excess", this depends on the threshold value (ALLOWED_WATER_INCREASE_M) which can be defined in the last step of the [[#Rain overlay wizard|rain overlay wizard]] or in the ''Keys'' section of the overlay. If the amount of water exceeds this threshold value, the amount of water is visible on the water bodies.
| |
|
| |
|
| | A [[Rainfall_Overlay_tutorial|Rainfall Overlay Tutorial]] is available to get you started with this overlay. |
|
| |
|
| | In order to get more familiar with the different components of the Rainfall Overlay check out Quadrant 2 of the [[Testbed_water_module|Water Module Testbed]]. This Testbed is available to you as a project in the {{software}}. |
|
| |
|
| ==Hydrological and Hydraulic concepts== | | ==Rainfall overlay results== |
| The current version of the rainfall overlay the following models are incorporated, shown in the schematic below: | | The Rainfall Overlay is a Water Overlay that is connected to the Water Module. This Water Module performs two dimensional grid based water simulations for a large set of input data and parameters, configured mostly through a related [[Water Overlay Wizard]]. When a simulation finishes, the module stores the result in the Rainfall overlay based on the selected result type. Only one result type can be stored per Rainfall overlay. |
| * A rainfall 2 runoff model, describing the transport of rainfall via roofs, paved and unpaved areas to the groundwater, sewer system and/or surface.
| |
| * A sewer model, describing the transport of water trough the sewer system.
| |
| * An inundation model, describing the process of overland flow (also referred to as sheet flow), when runoff exceeds the transport capacity of the sewer system.
| |
| * A groundwater model, describing the transport of water trough the sub-soil.
| |
| * A surface water model, describing the transport of water trough a polder system
| |
|
| |
|
| [[File:Rainfall_Overlay_schematic.png]] | | The Water Module however, is not restricted to generating only one type of result. Instead it can produce multiple unique result types for one single simulation. |
| | Fortunately it is possible to add additional result type overlays which relate to a particular Rainfall overlay. These are known as [[Result Child Overlay]]s. Again, each child overlay only stores one particular result type. |
|
| |
|
| Rainfall and evaporation are supplied as input data. Depending on the topography assigned to a cell ''rainfall'' contributes to storage (e.g. trees, roofs, etc) on paved (houses, roads, etc), unpaved (e.g. green zones) or open water areas from which ''evaporation'' can take place, depending on the topography of a cell. In case these storages are depleted: | | Apart from multiple result types, the Rainfall overlay can also store result data of multiple, intermediate simulation results, instead of just a single end result. These intermediate simulation results are known as [[timeframes (Water Overlay)|timeframes]]. |
| * In case of unpaved topography excess water contributes directly to surface ''(SCF)''
| |
| * Excess water from paved cells contributes to sewer storage ''(SIF)'' of the sewer district. If insufficient storage is available in the sewer district, water contributes to surface storage ''(SCF)''
| |
| From the surface storage water can directly infiltrate ''(INF)'' to the sub-surface if both the infiltration capacity and sub-surface storage is sufficient.
| |
|
| |
|
| Water can flow from cell to cell via the surface ''(RUN)'' via an 2D kinematic wave approximation of the shallow water equations. If surface runoff contributes to a cell with an open water topography in contributes to the storage of the water district. Cell to cell ground water flow ''(GWF)'' is possible respecting Darcy's law.
| | For the full list of result types, see [[Result type (Water Overlay)#List of Result Types|List of Result Types]]. |
|
| |
|
| The sewer system and surface water system are represented by districts. Water from sewer districts ''(SEW OUT)'' is assumed to be pumped to a treatment plant and extracted from the model domain. The surface water system can consist of multiple water districts (for now we use peilgebieden), which have a typical drainage level. Outflow from each district ''(DIST OUT)'' can be extracted from the model domain or contribute to another district via hydraulic structures. Currently weirs, culverts and pumps are incorporated in the model.
| | For other results, which are not overlay results, but still related to the simulation for a particular Rainfall overlay, see [[Results (Water Overlay)|Rainfall overlay results]]. |
|
| |
|
| ==Scope of application== | | ==Module== |
| The rainfall overlay is typically used to show effects of heavy rainfall (e.g. 30 mm/hour) in urban areas, in flat till mildly-sloped areas. It includes all processes describing what is commonly referred to as pluvial flooding or flash floods.
| | A Rainfall Overlay can be configured by opening the Rainfall Overlay Wizard. More in-depth information can be found under each of the categories below. |
| | {{Water Module buttons}} |
|
| |
|
| Please bear in mind the following:
| | ==References== |
| * So far, the rainfall overlay does not incorporate flooding due to mall-functioning sewer systems (surcharge) or flooding due to insufficient capacity of the surface water system.
| | # [[Water Module Theory#Formulas|Water model formulas]] |
| * The total simulation time is by default divided by 2000 time steps (referred to as cycles). When the total simulation time is increased, the amount of cycles can be increased when necessary to assure accurate results.
| |
|
| |
|
| | | {{WaterOverlay output nav}} |
| The overlay can be configured to display various results of the simulated rainfall. See below for the complete list of result types.
| | {{Overlay nav}} |
| | |
| ===Input Data===
| |
| When no input data is provided, results will be computed using default values and assumptions.
| |
| | |
| The model model can be refined by providing the following data:
| |
| *Fixed drainage level areas (peilgebieden)
| |
| *Hydraulic structures (culverts,weirs and pumps)
| |
| *Initial groundwater levels
| |
| *sewer districts (rioleringsgebieden)
| |
| | |
| ===Results===
| |
| * '''BASE_GROUNDWATER_DISTANCE''': shows the distance between the groundwater level. For now, the height of the ground level is including the buildings and other objects on the ground (the height to the surface). This will be changed to the terrain height in a following release.
| |
| *'''BASE_TYPES''': shows the division of the grid cells in water, land or sewer areas that are connected to the sewer. Playing with the grid cell size, will make this division between areas/terrain types more or less accurate, which affects the calculation of the flooding.
| |
| *'''EVAPORATED''': shows how much water is evaporated after the rainfall in the defined simulation time. For more information on how this layer is calculated, see the [[Rainfall overlay calculations]] page.
| |
| *'''IMPACTED_BUILDINGS''': shows all constructions or neighboring cells which will be flooded with the settings as provided in the rain overlay wizard and the IMPACT_FLOOD_THRESHOLD_M attribute (see attributes of the rainfall overlay). The result type shows therefore which constructions or neighboring cells are more flooded than the defined threshold. The colors are based on the attribute 'Critical infrastructure' in the function values table, in where a classification is made in the importance of flooding of different types of buildings. Three values can be entered in the function values table: 0 (not very critical, for example a shed or a park), 1 (important, most buildings), 2 (critical, such as a hospital or a school).
| |
| *'''SEWER_LAST_VALUE''': The amount of water remaining in the sewer after the simulation is over
| |
| *'''SEWER_MAX_VALUE''': The largest amount of water that was in the sewer at any time during the simulation
| |
| *'''SURFACE_DURATION''': The total amount of time the surface has water on it
| |
| *'''SURFACE_FLOW''': The total amount of water which has flowed across the surface
| |
| *'''SURFACE_LAST_VALUE''': The amount of water remaining on the surface after the simulation is over
| |
| *'''SURFACE_MAX_VALUE''': The largest amount of water that was on the surface at any time during the simulation. Differs from WATER_STRESS in that water stored on bodies of water is always included.
| |
| *'''UNDERGROUND_FLOW''': The total amount of water which has flowed underground
| |
| *'''UNDERGROUND_LAST_VALUE''': the amount of water which has flowed underground after the rain simulation is over.
| |
| *'''UNDERGROUND_MAX_VALUE''': the largest amount of water that flowed underground at any time during the simulation
| |
| *'''WATER_STRESS''': The maximum amount of excess water at any time during the simulation. Differs from SURFACE_MAX_VALUE because water stored on bodies of water are not immediately deemed "excess", this depends on the threshold value (ALLOWED_WATER_INCREASE_M) which can be defined in the last step of the [[#Rain overlay wizard|rain overlay wizard]] or in the ''Keys'' section of the overlay. If the amount of water exceeds this threshold value, the amount of water is visible on the water bodies.
| |
| | |
| | |
| Also, the influence of subsidence can be included in the calculations, see therefore the section about [[#Including_subsidence|including the subsidence overlay]].
| |
| | |
| ==Rain overlay wizard==
| |
| ===Configuring the rainfall overlay===
| |
| The rainfall overlay consists of several [[#Result_types|result types]] that show different analyses of the area after or during the extreme rainfall. The overlay can therefore be added to the project multiple times, to present different outcomes or scenarios and compare these, for example for different rainfalls. For information on adding and removing the overlay to and from the project, see the page about[[overlay#Adding and removing overlays| overlay]]s in general.
| |
| | |
| To improve the accuracy of the model:
| |
| *Use a grid size of max 2m for calculating the correct flow.
| |
| *Select the high resolution heightmap in the [[Wizard]] under advanced options, to use a high detailed height map (1 point per 0.5m).
| |
| | |
| To further enhance the way the calculations are made and make the model more accurate, the overlay itself can be configured. To guide the user along these configurations, the rain overlay wizard provides the steps to add data about the water system and/or configure hydrological coefficients used in the calculations.
| |
| | |
| ===Rainfall===
| |
| The wizard exists of several steps. First the intensity and the length of the [[weather|rain definition]] is set. The simulation time of the model compromises the length of the rainfall and the time it takes before it is dry. Also, the simulated rainfall will be equally distributed over the time.
| |
| In the following steps, data about the water system can be provided.
| |
| | |
| ===Water level areas===
| |
| Here you can add your own dataset of "level areas" with a set water level. This file is loaded in as a [[geojson]] file as areas. The following attributes are needed for the calculations.
| |
| {| class="wikitable" | |
| ! Attribute
| |
| ! Description
| |
| ! Example
| |
| ! Remark
| |
| |-
| |
| | NAME
| |
| | The name of the water level area.
| |
| | PG 256
| |
| | This attribute is not loaded in as attribute, but can be used as name to identify the resulting area in the Engine later on.
| |
| |-
| |
| | WATER_LEVEL
| |
| | The height of the water, in meters, measured from Amsterdam Ordnance Datum (mNAP).
| |
| | 1.6
| |
| | For a water level area with infinite storage, this can be set to an extreme negative number (e.g. -9999). However, note that this would also place this area far below level areas with a proper height set.
| |
| |-
| |
| | OUTLET
| |
| | The amount of water which disappears from this level area in cubic meters per second (m3/s).
| |
| | 0.007
| |
| | This could also be the outlet of a ''gemaal''
| |
| |}
| |
| If you do not have any water level dataset, you can also generate a water level area. This will create one waterlevel area which covers the entire 3D world, with no OUTLET value and a WATER_LEVEL of -1000.
| |
| In the wizard the attributes which contain values for the water level and outlet need to be set. If they have different names, these can be chosen in the ''select attribute table''.
| |
| | |
| ===Hydrological constructions===
| |
| For example weirs form connections between water level areas, where the water is transported from higher to lower water level areas. The weir (or other hydrological construction) dataset is also loaded in as a [[geojson]] file. The following attributes need to be present.
| |
| {| class="wikitable" | |
| ! Attribute
| |
| ! Description
| |
| ! Example
| |
| ! Remark
| |
| |-
| |
| | NAME
| |
| | The name of the weir.
| |
| | PG 256
| |
| | This attribute is not loaded in as attribute, but can be used as name to identify the resulting contruction in the Engine later on.
| |
| |-
| |
| | WEIR_HEIGHT_M
| |
| | The height of the weir, in meters, measured from Amsterdam Ordnance Datum (mNAP).
| |
| | 1.8
| |
| | When using this model outside of the Netherlands, the height is in the same scale as the [[Terrain height]] of the project. When an extreme negative value is used, the construction acts like a culvert.
| |
| |-
| |
| | WEIR_SPEED
| |
| | The speed at which water is moved from one level area to the other, in cubic meters per second (m3/s).
| |
| | 0.007
| |
| | Once the water level exceeds the height of the weir, the water flows at this constant speed until the water level no longer exceeds the height of the weir.
| |
| |}
| |
| This file is loaded in as [[construction]]s. For now, the underground construction ''drainage system'' can be used.
| |
| If no weirs exist, there are no connections between water level areas and water is not transferred between them.
| |
| | |
| Weirs must overlap with at most 2 water level areas. If a weir overlaps with more that 2 water level areas, 2 areas are selected at random which the weir pumps between. If a weir overlaps with only 1 water level area, only its outlet function is processed. Weirs which do not overlap with any water level areas have no effect.
| |
| | |
| ===Ground Water level data===
| |
| This step in the rain overlay wizard provides the possibility to upload a GeoTiff file with ground water levels. By default the ground water level of the water level areas is used. If you choose for the option to upload a GeoTiff file, you can add you own GxG map with the distances between the ground level and the ground water level in meters. Or you can use one of the already loaded in GxG maps.
| |
| | |
| ===Sewers===
| |
| The next step allows for the sewer areas to be uploaded. The file is loaded in as a [[geojson]] file as [[area]]s. The following attributes are needed:
| |
| {| class="wikitable"
| |
| ! Attribute
| |
| ! Description
| |
| ! Example
| |
| ! Remark
| |
| |-
| |
| | NAME
| |
| | The name of the sewer.
| |
| | Sewer North-East
| |
| | This attribute is not loaded in as attribute, but can be used as name to identify the resulting area in the Engine later on.
| |
| |-
| |
| | SEWER_PUMP_SPEED
| |
| | The speed at which water is pumped out of the sewer, in cubic meters per second (m3/s).
| |
| | 1
| |
| | All areas which are not plots of this kind should either not have PERCEEL as an attribute, or should have it set to 0(*).
| |
| |-
| |
| | SEWER_STORAGE
| |
| | The amount of water which can be stored in this sewer, in meters (m).
| |
| | 0.007
| |
| | The total amount of storage for this sewer is the surface area of the [[construction]]s which are connected to the sewer in this particular sewer area, times this attribute.
| |
| |}
| |
| If no sewers exist, the model has no water flowing into sewer containers for storage. Therefore, you can automatically generate these areas. For more information on how the generation of these areas is done or about the sewer system in general, see the [[Rainfall overlay calculations#Sewer system|Rainfall overlay calculations]] page.
| |
| | |
| ===Hydrological coefficients===
| |
| In the next steps of the wizard, hydrological coefficients regarding the surface and the underground terrains, can be edited.
| |
| For each of these coefficients, representative values are already entered in the forms.
| |
| *Water infiltration (m per day): the speed by which the water infiltrates the underground. The speed is also determined by the underground water infiltration factor. From these two values, the lowest value is used.
| |
| *Water manning: the Gauckler Manning coefficient, often denoted as n, is an empirically derived coefficient, which is dependent on many factors, including surface roughness and sinuosity. For more information about this formula see [[Rainfall_overlay_calculations#Manning_formula(surface_runoff)|the Rainfall overlay calculations page]].
| |
| *Water evaporation factor: this factor will be multiplied with the general reference evaporation.
| |
| *Reference Evaporation (mm per day): The Makking reference evaporation factor. This value ranges from 0.5 mm per day in the winter till 3 mm per day in the summer for the weather station ‘ De Bilt’ in the Netherlands.
| |
| *Water storage fraction: the percentage of underground volume that can be used for the storage of water. This number is determined by the difference between the ground water level and the surface height times the surface area.
| |
| *Vertical to horizontal infiltration factor: This factor will be multiplied with the vertical infiltration speed, to obtain the horizontal infiltration speed.
| |
| | |
| [[File:Visualisatie_wateroverlast.JPG|400px|thumb|right|Schematic visualization of the water flow over the water level areas and hydrological constructions.]]
| |
| ===Building functions===
| |
| Since [[construction]]s in the Engine have an effect on the flow of the water, for example if a building has a green roof, attributes concerning these values can be adjusted in this step of the wizard. Representative values are already entered in the table. The same values can also be adjusted in the [[Functions#Editing functions|function values window]].
| |
| | |
| ===Visualization of the water system===
| |
| In the last step you can choose for a [[#Result_types|result type]], as listed above. If you have provided the water level areas and the hydrological constructions to the Engine, along with the required attributes, a schematic visualization of the water flow from the various water level areas and the hydrological constructions is visible. The red spheres stand for water flowing from a weir to another water level area. The green spheres stand for a weir receiving water from a water level area. The speed of the spheres is based on the WEIR_SPEED and the OUTLET values. If no spheres are visible, the water flows very gently between these water level areas. The pop-ups in the 3D world are panels which mark the middle of the water level area or the place of the hydrological constructions. In these panels, the provided attributes, such as the WATER_LEVEL_M or the WEIR_HEIGHT can also be edited. Play around with this to see how the water flow changes.
| |
| | |
| ===Including subsidence===
| |
| [[File:Subsidence_attribute.JPG|400px|thumb|right|Create a new attribute containing the recalculated water levels.]]
| |
| [[File:Include_subsidence.JPG|400px|thumb|right|Include the subsidence overlay and select the new water level attribute.]]
| |
| For the calculation of the effects of a severe rainfall, effects of subsidence can be included, such as the recalculated water levels and the changed ground levels. For now, ground water levels affected by the subsidence are not included.
| |
| | |
| {{Editor steps|title=include subsidence|Add the [[Subsidence_(Overlay)|subsidence overlay]]. Take note of when to use and how to configure the subsidence overlay.|In the [[right panel]], select the "Keys" tab|Select the "Area attribute: output level (m)". Choose a new attribute, for example the WATER_LEVEL_OUTPUT attribute, to write the new water levels to. |In the Rainfall overlay in the [[right panel]], select the "Keys" tab.|Choose the overlay for the subsidence model you want to use in the "Include Subsidence" form.|Also select the newly created attribute containing the water levels in the "Area Attribute: Water Level (m)" form.|Go to the "General" tab and recalculate the grid.}} | |
| | |
| Be careful not to write the new water levels calculated in the [[Subsidence_(Overlay)|subsidence overlay]] to the already existing water level attribute, otherwise the subsidence model will be recalculated with incorrect values when refreshing this overlay.
| |
| | |
| You can play around with the results of the two overlays and compare, for example, two rainfall overlays where one overlay takes the effects of a subsidence model into account and the other overlay shows results without these effects.
| |
