With the changing of the seasons, the implications of Stormwater Compliance will look different. Stormwater Compliance isn’t limited to rainfall events during summer – it includes any significant precipitation event and other contributing factors. Colorado’s weather can be unpredictable and each season will bring its own challenges making stormwater compliance a year-round responsibility. There are important factors to consider for each season:
Fall: Increased Debris and Vegetation Die-Off
As the weather starts to cool down and leaves/vegetation begin to fall, it can cause excessive build up around BMPs such as inlet protects, check dams, and VTCs which will limit their functionality. Cooler weather also slows vegetation growth, which is an important note to consider when planning stabilization (both permanent and temporary). As vegetation starts to go dormant, soil also loses its stability, which increases erosion risk. If a project plans to be inactive heading into winter (for example, many projects become inaccessible at higher altitudes), inspection frequencies can/may be reduced to monthly. Make sure your SWMP adequately reflects any changes in both protocol and BMPs.
Winter: Freeze–Thaw Cycles and Snowmelt Issues
When temperatures drop below freezing, the frozen ground restricts infiltration causing larger impervious surface areas. With the intense sunshine, temperatures can quickly rise again above freezing, creating “freeze-thaw cycles” that will affect ground infiltration and can damage BMPs or reduce their effectiveness. Weather may also inhibit BMP maintenance, however it’s important to strive to remain compliant even during winter months.
Snow storage and deicing materials can also create pollution sources if not properly managed. It’s important to note that snowfall itself is not automatically considered a significant precipitation event — because runoff does not occur until snowmelt happens. Meltwater can carry salts, sand, and pollutants into waterways. Post-storm inspections during winter months should be conducted within 24 hours after measurable snowmelt occurs.
Spring: Rapid Snowmelt and High Runoff Volumes
As snow consistently melts, run-off volumes surge. Any sediment or debris build up that had been previous frozen or stationary can easily be dislodged during melting events. If BMPs have not been regularly maintenanced during the winter, they can be damaged with the increased flow of water. Projects coming out of winter conditions must reactivate their Stormwater Management Plans (SWMPs), replace damaged controls, and reestablish vegetation.
Summer: Intense Storm Events
During summer, short powerful thunderstorms create high sediment transport and erosion risks. The dry, compacted soils after drought conditions can increase initial runoff. It’s crucial BMPs receive frequent inspections and maintenance to handle fluctuating weather extremes.
Colorado’s year-round temperature swings, precipitation variability, and elevation differences mean stormwater management can’t be a “set it and forget it” task. Each season requires proactive planning, inspections, and adjustment of BMPs to stay compliant and protect local waterways.
Need help preparing your stormwater site for winter? Summit can help with SWMP updates, inspections, and seasonal BMP management.