comparison of run off hydro-graphs

Hello, 

once running a storm event in OpenFlows FLOOD, the catchment areas, that you need to delineate in CivilStorm for each inflow node, is not an required input to determine the contribution area, since the Digital Surface model together with 2D calculation (Saint-Venant and Manning-Strickler equations) will do it. Same happens with Time of Concentration input, that is also taken by the surface´s conditions, while in CivilStorm is another user input.

Another situation that can happens while applying the 2D calculation is when you have depressions that causes water ponding, something that you need to enter in CivilStorm explicitly, while in 2D calculation it´s seen as a result.

I believe this topics above bring the differences regarding the runoff calculation in CivilStorm and OpenFlows FLOOD.

Hope that helps.

regards,

Douglas MIranda.

Thanks for the reply... I see you raised an important point regarding local depressions in an area. I was thinking in the context of say an undeveloped land catchment area  which generates run off that I want to load to a culvert in CivilStorm. Typically you would add the catchment, define area, CN, Tc, hyetograph...etc and the CivilStorm run will generate a run off hydrograph for this catchment using SC that it will convey to the catchment outlet being the culvert in this case. This will ignore any depressions within that might result in ponding and hence that ponding water may never be part of actual run off that reach the outlet/culvert. Whereas 2D analysis will capture that.

Does OpenFlow Floods take the total precipitation depth rainfall hyetograph and applys a loss method or do you need to do the catchment hydrology on the side and input the excess rainfall hyetograph to the model?

You can enter information regarding the soil permeability (fraction number) that can be a unique value for all basin or based in a grid file to determine where infiltration is higher and where is lower.

About surface depressions, if they are not welcomed in the modeling, OpenFlows FLOOD has tools to remove it.

Just to complement Douglas answer:

OpenFlows FLOOD 2D modeling engine (MOHID Land) is able to calculate internally the water losses and movements, based on the parameterizations and processes that you plug in: water that reaches the surface (from rain), can then infiltrate, evaporate (evapotranspiration), enter river / surface channel drainage network or a subsurface stormwater drainage network. All these movements can be computed internally (depending on the processes that you connect). For instance, you can activate evapotranspiration: which is the sum of water evaporated from soil, canopy storage, surface water column and from plant transpiration. Reference evapotranspiration can be provided by user or calculated (Penman Monteith and water availability in soil).

As regards to infiltration process, MOHID Land can compute internally the water movement from surface to the soil, and then simulate the water hydrodynamics through the soil: water can eventually recharge a groundwater aquifer; can evaporate (evapotranspiration), be consumed by vegetation, or even exfiltrate. In OpenFlows FLOOD we’re able to simulate the whole processes. We can simply compute infiltration using SCS curve number method, or other methods such as Green Ampt equation or Richards equation.

Adding to this, as Douglas mentioned, we can also include an impermeability fraction (by default, is 0).

Hello,

The responses to this thread and additional information are now documented in the following wiki article;

Runoff Comparison between CivilStorm / SewerGEMS and OpenFlows FLOOD

Hope this helps.