This time of year, each snowfall in Indianapolis and central Indianapolis is accompanied by this question posed by many Hoosiers — “Is this the last snowfall of winter?” While Indiana is sometimes blanked with a few more inches of the white stuff throughout the month of March (and even some into April!), we are also anticipating warmer temperatures and the great thaw that they bring.
The mountains of snow plowed in parking lots shrinks daily. The thick layer of ice on our central Indiana lakes becomes dirty and cloudy, and soon thaws completely. Springtime also brings with it another form of precipitation — rain. And often HEAVY rain. Either one of these — the melt-off or heavy rains — would be enough to cause the potential for localized flooding, but coupled together, we are almost guaranteed to see flooding in some areas of central Indiana at different times during the spring season.What factors contribute to this weather phenomenon and how can you prepare and protect yourself and property?
According to the National Oceanic and Atmospheric Association (NOAA), these are some of the factors that contribute to snow-melt flooding.
- High Soil Moisture Conditions Prior To Snow-melt
Rainfall during the late fall causes the soil to be more saturated.
- Ground Frost Or Frozen Soil
Central Indiana has experienced freezing temperatures or below for several weeks now, causing hard ground frost which prevents snow-melt from infiltrating the soil.
- Heavy Winter Snow Cover
Widespread and heavy snow cover means there is more water stored and available for snow-melt.
- Widespread Heavy Rains During The Melt Period
Rain at this time contributes more water for flooding. Also, heavy rain can warm up cold snow-packs, causing them to melt more quickly. “Rain-on-snow” events are watched carefully for this reason.
- Rapid Snow Melt
Most often, snow-melt is a relatively slow phenomenon. Snow-melt rates are usually comparable to light-moderate rainfall. Important exceptions to this can occur, especially during unusually warm periods with high dew point temperatures (humidity), and when nighttime temperatures remain above freezing. Snow-melt rates can be much higher than normal under these conditions.
- Ice Jams In Rivers
Snow-melt and the breakup of river ice often occur at about the same time. Ice jams sometimes occur, often in response to higher, fluctuating river flows associated with snowmelt. Ice jams can act as dams on the river that result in flooding. For this reasons, locations along central Indiana waterways should be especially vigilant.
Prepare For Flooding In Central Indiana
The Centers for Disease Control and Prevention (CDC) give the following advice.
Preparation — When Flooding Is Predicted
While some preparation should be done well in advance of likely flood conditions, even when flooding is imminent, there are steps that can be taken. Contact the local county geologist or county planning department to find out if your home is located in a flash-flood-prone area or landslide-prone area.
Learn about your community’s emergency plans, warning signals, evacuation routes, and locations of emergency shelters. Plan and practice a flood evacuation route with your family. Ask an out-of-state relative or friend to be the “family contact” in case your family is separated during a flood. Make sure everyone in your family knows the name, address, and phone number of this contact person. Post emergency phone numbers at every phone and add them to the contact list of your mobile phones.
Identify potential home hazards and know how to secure or protect them before the flood strikes. Be prepared to turn off electrical power when there is standing water, fallen power lines, or before you evacuation. Have a licensed electrician raise electric components (switches, sockets, circuit breakers and wiring) at least 12″ above your home’s projected flood elevation Turn off gas and water supplies before you evacuate. Secure structurally unstable building materials. Buy and install sump pumps with back-up power.
For drains, toilets, and other sewer connections, install back-flow valves or plugs to prevent flood waters from entering. Anchor fuel tanks which can contaminate your basement if torn free. An un-anchored tank outside can be swept downstream and damage other houses.