# Stormwater Management & Drainage
Development adds **impervious surface** (roofs, pavement), which creates more and faster runoff. Regulations require you to **manage that water** so you don't flood neighbors or pollute streams.
## What's required
- **Detention/retention** — ponds or underground vaults that **hold back** runoff and release it slowly, so peak flow after development isn't worse than before.
- **Water quality treatment** — removing pollutants (sediment, oils) before discharge, often via ponds, bioretention, or filters.
- **Conveyance** — storm pipes, inlets, swales, and outfalls that move water safely off-site.
## Why it dominates civil design
Stormwater often **consumes a big chunk of the site** (ponds take land) and budget. Designing it efficiently — and early — protects both your yield and your pro forma.
**Takeaway:** Design stormwater early; ponds eat both land and budget.
> *Educational content — not legal, engineering, or financial advice. Requirements vary by jurisdiction; always confirm with the local authority and your professional team.*
