hi guys
I am a new user of SWMM 5
i am using it for my thesis on urban flooding. Can you help me explain these terms:
- ponded depth : is this the depth of surface water from the rim elevation. in my model, if a node is flooded, then this number equals to the max depth ?!?
- max surcharge : is this the max depth of water as the water reaching to the rim ?
- runoff depth: is this the surface flood depth ? from my understanding epa SWMM is 1d model and therefore cannot explicitly simulate the surface flood depth .
Is there a way to estimate the flood depth ?
Tks
Replies
Runoff Depths for different Subcatchments should be different if the data for the Subs is different
Note: InfoSWMM or SWMM 5 Basic Runoff and Other Wet Weather Processes
Subject: 3 Types of Manholes in SWMM 5 and InfoSWMM
There are three types of interior manholes in SWMM 5 and InfoSWMM as regards water surface elevations above the Node Rim Elevation:
1st Excess Water leaves the Node as flooded water if the water surface elevation equals the Rim Elevation (Figure 1 and Gravity Mains),
2nd Excess Water is stored in the manhole as pressurized depth if the Node Surcharge Depth is used (Figure 2 and Force Mains)
3rd Excess Water is stored above the Node Rim Elevation (Surface Ponding and Figure 3)
Figure 1. The default node in SWMM 5 and InfoSWMM has just the Manhole Invert Elevation, the program calculated elevation of the highest connected link and the Node Maximum Depth or Rim Elevation. If the Water Surface Elevation exceeds the Rim Elevation then any excess flow is lost as flooded flow.
Figure 2. A force main or pressure in SWMM 5 and InfoSWMM has the Manhole Invert Elevation, the program calculated elevation of the highest connected link, the Node Maximum Depth or Rim Elevation and the Node Surcharge Depth. If the Water Surface Elevation exceeds the Surcharge Elevation then any excess flow is lost as flooded flow but this allows more the links to have more pressure and hence more flow.
Figure 3. The flooded Node option in SWMM 5 and InfoSWMM has just the Manhole Invert Elevation, the program calculated elevation of the highest connected link, the Node Maximum Depth or Rim Elevation and Node Ponding. If the Water Surface Elevation exceeds the Rim Elevation then any excess flow is NOT lost but stored in the ponded area. The depth of the ponded area is a function of the ponding area and the excess inflow. If the water surface elevation goes below the Rim Elevation then the ponded volume flows back into the network.
tks bob
I still have some concerns:
If a ponded allowed node is flooded, then the excess water will be stored in a ponded area. Therefore is the runoff depth on the respective catchment can be "understood" as a suface flood depth ? I need this information to develop a flood hazard map.
thank you
The node and catchment depths are separate items. The Runoff Depth is over the catchment and the node depth is based on the hydraulics of the network. Runoff goes into the hydraulics network and then either gets routed or comes back out as a flooded node
SWMM 5 Flooding Volumes for Ponding and Without Ponding
- ponded depth : is this the depth of surface water from the rim elevation. in my model, if a node is flooded, then this number equals to the max depth ?!? The ponded depth is the depth in the ponded area, so it plus the maximum depth of the node equals the maximum depth during the simulation.
- max surcharge : is this the max depth of water as the water reaching to the rim ? The depth above the pipe crown going into or out of the node
- runoff depth: is this the surface flood depth ? from my understanding epa SWMM is 1d model and therefore cannot explicitly simulate the surface flood depth . It is a 1D model but the runoff depth is the depth over the catchment and is the depth you get from the rainfall minus the infiltration, evaporation and runoff. It is not a 2D Mesh but a three box model of the Catchment - impervious, impervious without depression storage and pervious area
The surcharge depth from the node attribute table is added to the maximum full depth in the routine dynwave.c as an upper bound check for the new iteration depth of yNew.
// --- determine max. non-flooded depth
yMax = Node[i].fullDepth;
if ( canPond == FALSE ) yMax += Node[i].surDepth;
If the new depth yNew is greater then yMax then the program will calculate either the amount of flooding from the node or the ponded depth and volume. If the node cannot pond (canPond is False) then the amount of overflow is the excess flow in the node and the new depth yNew is set to yMax.
if ( canPond == FALSE )
{ Node[i].overflow = (Node[i].oldVolume + dV - Node[i].fullVolume) / dt;
Node[i].newVolume = Node[i].fullVolume;
yNew = yMax; }
else {
Node[i].newVolume = Node[i].fullVolume + (yNew-yMax)*Node[i].pondedArea;
Node[i].overflow = (Node[i].newVolume - Node[i].fullVolume) / dt; }
if ( Node[i].overflow < FUDGE ) Node[i].overflow = 0.0;
return yNew;