Rainfall Overlay

What is the rainfall overlay

Calculation steps

Here there should be an overview of all the calculations steps. BOB: Flowchart?

Rainfall

Water is created in the form of rainfall. Properties of rainfall the amount of water created per calculation step is based on the amount of calculation steps for the simulation, the duration of the rain, and the amount of rains which falls during that time. Directly after being created by rainfall, water can be placed in one of the follow containers:

Container	Condition
Sewer	If there is a SEWER area present, which is defined by the presence of a non-zero SEWER_STORAGE attribute, and there is a building present with the SEWERED attribute ("Connected to Sewer") set to 1, and the sewer container is not yet full, the water is moved directly into the sewer.
Building storage	If there is a building present with the WATER_STORAGE_M attribute ("Water Storage (m3/m2) )") set to a value greater than 0, and the building container is not yet full, the water is moved directly into the building container.
Surface water	If there is surface water present (i.e. a terrain with the WATER attribute set to 1), the water is moved into the surface water container.
Surface container	If there is no building connected to an empty sewer, no building with water storage, and no water terrain, the water is placed in a surface container.

Surface container

Surface containers

Water in a surface container is resting on the surface of the world. During a calculation step, the water can moved to one of the following containers:

Container	Condition
Underground container	An amount of water is transferred from the surface container to the underground container, based on the formula for vertical infiltration. Note: after calculating vertical infiltration, the following flow calculations are also performed.
Surface water	If there is surface water present (i.e. a terrain with the WATER attribute set to 1), the water is moved into the surface water container.
Surface container	If there is no building connected to an empty sewer, no building with water storage, and no water terrain, the water is placed in a surface container.