In this monthly feature, we span the globe to examine Our Changing Landscape with time series of medium resolution RapidEye satellite imagery. The RapidEye archive dates back to late 2008 and already contains more than 4 billion square kilometers of data. This month, we look at the impact of the ‘Great’ Boulder Flood on the town and surrounding communities.

The RapidEye Constellation

RapidEye is a constellation of five 5-meter medium resolution satellites each offering five spectral bands of information. The RapidEye constellation offers a daily revisit time to every location on the planet with a huge footprint that is 77-km wide. The data is priced competitively with a base price of $1.28 per square kilometer for all five spectral bands – academics do receive discounts. RapidEye adds a fifth band, the red edge, to the ‘traditional’ multispectral set of blue, green, red and near-infrared (NIR). The additional spectral data available in the red edge band allows users to extract more useful land ‘information’ than can be from traditional 4-band imagery sources. When RapidEye imagery is ordered as a Level 3A Orthorectified product, images from multiple dates are extremely well registered, making it the ideal data source for Our Changing Landscape.

Click on the image above to see an animation of 5-meter natural color imagery collected over Boulder, Colorado on July 17 and September 21, 2013. We have normalized the colors of these two images as much as possible to give our viewers a better sense of the flood’s impacts. In this first set of images, you can see multiple ‘temporary’ rivers that were formed along the Front Range, they appear as new paths of bare reddish soil. On Thursday evening, these rivers would have been raging with water more than 4 feet deep! You can also see the extent of change along the shores of the river that snakes through the center of this image and exits to the southeast. (Images Courtesy: RapidEye)

The ‘Great’ Boulder Flood of 2013

Was it a 100-year flood? Maybe the 1000-year flood? Or perhaps a 100-year rain? Even a 1000-year rain? While I have seen this topic discussed in many a news article, I will leave this debate for the meteorologists and climatologists; and instead focus in this short piece on one Boulder-ite’s experience during the ‘Great’ Flood of Boulder.

It all started innocently enough on the Monday of that week (September 9^th) with some gentle rainstorms that felt refreshing after a stretch of hot, late summer weather. Countless people commented that day on how amazing the change of weather was in a town with more than 300 days of sun per year. The rains continued into Tuesday and seemed to intensify during the day on Wednesday. It was starting to feel a bit odd by Wednesday as three straight days of rain in Colorado is unusual to say the least, but I do not think anyone predicted what would happen next.

The Wednesday rains continued into the evening with frequent and powerful downpours. I remember sitting on my couch at 10PM, listening to the rain and watching some news when the weather alert sirens went off. It was the first time I have ever heard the sirens used for anything other than a test. The lady and gentleman on the loud speaker warned of flash flooding on the Boulder Creek and declared that no one should attempt to cross the raging waters. While it seemed odd and definitely a bit spooky, sleep followed shortly thereafter.

Click on the image above to see a second animation of 5-meter natural color imagery collected over Boulder, Colorado before and after the ‘Great’ Flood. Since colors have been normalized across these dates, you can see just how much mud and silt was deposited on the roads of downtown Boulder. The red roofs here are those of the campus of University of Colorado. Just to the north is the path of the Boulder Creek which overflowed its banks and damaged multiple structures in the floodplain. (Images Courtesy: RapidEye)

Thursday morning started as would any other day – a little national news, tea and work emails. Katie arrived around 8AM that morning and it was still raining. Neither of us spent any time on local media that day so we had little sense of the rising waters and the damage they were causing. In fact, the rain stopped at midday so Katie and I used the break in the weather to take a walk down to the Boulder Creek, which is about 10 minutes from our office, to survey the damage. I have lived in Boulder for over 10 years and I have never seen anything like it – the Creek was well over its banks and had flooded areas more than 20 feet away. While it was a novelty that warranted a few photos, the gravity of the situation still had not sunk in. By Thursday afternoon, the rains started again, Katie left for home early and it fell dark again.

The rains continued into the evening and around 10PM again, the alerts over the loud speakers started for a second night in a row. This time the gravity of the situation did sink in. I received multiple texts from friends that were evacuated and were dealing with flooded/flooding basements. I monitored the Boulder Office of Emergency Management throughout the evening to stay on top of breaking news. And spent time watching the unfolding disaster on local news.

By the time the sun rose Friday morning, the rains had died down and the full extent of the Great Flood was obvious. What made this flood unique too me was the spatial distribution of the destruction. In the past, I understood a flood as an event that started with a river over-flowing its banks and wreaking havoc on the surrounding homes and property. The Boulder Flood was very different however. Yes the Creek did flood and cause damage as one would expect; but the real damage was caused by roads, ditches and other low places that became raging torrents of water even though they were miles from the closest small stream. Fueled by accelerated run-off from the steep and often sparsely vegetated hills above the town, these temporary raging rivers were extremely dangerous and damaging as they carried trees, cars, boulders and anything they overtook. In the end, it was these ‘rivers’ that caused the most damage and were the most visible impact of the Great Flood.

As any strong community does, cleanup started Friday with neighbors helping neighbors and everyone doing their part. Two weeks have past now and life is returning to normal here in Boulder but that is not the case for many of the surrounding mountain communities such as Jamestown, where the devastation was profound and of epic proportions.

This animations of RapidEye imagery gives us an excellent sense of the scope of the disaster here in Boulder. Our collective Apollo Mapping hearts go out to all the victims of the Flood and to those who are rebuilding from it.

If you would like to find out more about using RapidEye for your academic studies, engineering projects or any landscape analysis, let us know at sales@apollomapping.com or (303) 993-3863.