In comparison, continuous simulation applies a long term record of rainfall directly within InfoSWMM H2OMap SWMM InfoSWMM SA to generate a long-term record of simulated runoff statistical analysis is then run on this generated record to characterize the long-term performance and achieve a final design. the 2-hr 10-yr design storm) and are used within InfoSWMM H2OMap SWMM InfoSWMM SA to generate a single runoff hydrograph for design. In single-event simulation the rainfall record is first analyzed separately to create an Intensity-Duration-Frequency (IDF) curve from which design storms can be chosen these design storms have a specific duration and return period (e.g. Drainage system and detention pond ( SU1) designed in Example 3 9.2 System RepresentationĬontinuous or long term simulation involves the simulation of multiple events over a continuous period of months to years. What statistical properties of the rainfall record set it apart from the design storms used previously?įigure 9-1.How effective is the pond in capturing the majority of runoff events within its water quality control volume?.How effective is the detention pond in reducing peak discharges?.How significant are antecedent conditions in affecting system behavior?.How significant is evaporation within the overall system water balance?.Was the flow target used to design the detention pond adequate?.The results of the simulation will be analyzed with regard to the following questions: The performance of the conveyance system and the detention pond will be studied over the ten year period of 1968 to 1978. In this example the site will be analyzed using continuous rainfall records from the city of Fort Collins, CO that were downloaded from the National Climatic Data Center (NCDC) along with a set of monthly average evaporation rates (in/day). The system includes a BMP detention pond ( SU1) that was designed to provide a water quality capture volume for the more frequently occurring small storms and also provide peak runoff control for the 2-, 10- and 100-yr design storms of 2-hr duration. Continuous simulation considers all of these factors and allows for a more accurate and robust comparison of the long-term water balance and hydrologic performance of alternative stormwater management scenarios.įigure 9-1 shows the drainage system model developed in Example 3 for a new residential development on a 29 acre site. These single event design storms do not take into account varying patterns of rainfall duration and intensity, variation of time between storms, changing antecedent soil and storage conditions within the watershed, and the effect of evaporation. Drainage systems are typically designed using synthetic design storms. Because it only takes a few steps to set up Example 3 for a continuous simulation, the bulk of this chapter will focus on analyzing the results produced by the simulation.Ĭontinuous simulation is important because it allows actual historic data to be used to analyze the performance of drainage systems and their components. The use of InfoSWMM H2OMap SWMMInfoSWMM SA''s Output Statistics Manager tool for analyzing the results of a continuous simulation will also be demonstrated. This model will be re-run using a set of monthly average evaporation rates and a continuous precipitation record, so that its behavior over a 10year period can be studied. The multipurpose pond was designed to detain a water quality capture volume (WQCV) and control peak post-development release rates to their pre-development levels for the 2-yr, 10-yr and 100-yr design storms. It will analyze the performance of the drainage system and BMP detention pond for the 29 acre residential site designed in Example 3.
#Pcswmm 7.1 how to
This example shows how to run a continuous simulation with InfoSWMM H2OMap SWMM InfoSWMM SA using a long-term rainfall record. Continuous Simulation in InfoSWMM and InfoSWMM SA