Abstract

Of the computer applications currently widely used in civil engineering, hydrological modelling has been mostly restricted to discrete events. However, with improved affordability of powerful computing, long-term continuous modelling has now become much more attractive. At the same time, long-term urban impacts on water quality have also become an important design concern recent years. Continuous simulation is known to be a fundamental and reliable method for modelling nonpoint source pollution and its long-term effects on aquatic habitat. In the past, the main argument against using continuous modelling been the difficulty of managing large amounts of input and output data. A very large portion of this data is time-series (TS) in nature and requires special time series management (TSM) software. Different data formats and software also cause difficulties for continuous modelling of stormwater management. Our purpose in this effort is to provide code that mitigates these arguments against continuous modelling.

A survey of modellers was conducted to confirm the necessity and importance of developing easy-to-use software that assists long-term continuous modelling. A graphical user-interface called CASCADE2 was designed and developed to integrate the Hydrologic Engineering Center Data Storage System (HECDSS) wth the Storm Water Management Model (SWMM). Our purpose is not to integrate HEC application programs with SWMM, but merely to facilitate the easy export and import of datasets from HECDSS to SWMM.

CASCADE2 automatically manages and processes hourly and 15-minutely TS data for use with continuous SWMM. It allows the user to export or import any amount data from HECDSS by creating a dynamic macro, which overcomes the limitation in HECDSS of export or import of only monthly data. Storm-event statistics can also be computed by CASCADE2 automatically, and a summary file which includes station information, the total depth of rain, and the top ranked storm events is given at the end. Both SWMM and HECDSS program are run within CASCADE2, which thus acts like a shell, designed for application in typical, busy design offices. A performance assessment of CASCADE2 in terms of computational speed and storage space is provided. A panel of professional engineers tested CASCADE2 and the results are summarized. Long-term TS data can now be collected, stored, and retrieved in minutes not days, as compared to conventional efforts.

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