Why oh why?

This Blog is brought to you by the pitfalls and dangers of using fancy computer programs to model the real world. As you have noticed, I'm desparately scrambling to complete my senior design project so that I can graduate and get my iron ring and a job and that fancy Echo. . . and I'm modelling stormwater. Now, I want to say first that I hope that I'm lucky enough to spend the rest of my career in the field of stormwater management. It is biology, forestry, and civil engineering in a challanging package. It is has lots of research potential and in spite of numerous modelling programs - it is a field with numerous outlets (pardon my pun) for creativity.

However, that said, my current project is proving frustrating owing to the demons and pixies playing pranks in EPA SWMM. It appears that the runoff volume and peak flow rate before development is significantly larger than after development. This is noteably contrary to convential wisdom where paving large areas of land reduces infiltration and quickly shunts the runoff away. So, what is causing this discrpency?

I supect that the "pristine" model is short circuiting and dumping a shocking 82% of its runoff into the pond below compared to 68.5 % of the runoff from building and parking lots conveyed in sewers. So, its back to the land of reading help files for me - I've been doing this alot lately and hopefully I can let you know when I solve the mystery. Of course, in a few hours I may have something to say about the helpfulness of help files that may not be too complementary.

Until then - models may be easier and take into account more factors, but if you don't know them well, they can easily make assumptions for you that you have no way of tracing. And sometimes they are more work and give you results that are no better than the simple, blunt method. . .

Cheers,

Jennith