 People have always been attracted to rivers. Early settlers built near rivers because they were the only source of power and transportation. Today the reasons may be different, but the trend is still the same. However, there's often a price to pay for living with a river, and that's the threat of one of nature's most destructive forces, flooding. Hi, I'm Kevin Murray. And below me is the city that's probably best associated with flooding, Johnstown, Pennsylvania. Today we're going to look at residential construction in riverine areas, the different flood characteristics you have to look out for, and some construction techniques that will help keep you and your home from becoming the next flood statistic, building near rivers. That's the topic today on Best Build. Exactly 100 years ago, in May of 1889, heavy rains and runoff resulted in the failure of an improperly built earth-filled dam on the Little Panama River. A wall of water reported to be 50 feet high and moving over 40 miles per hour, rushed through the valley, carrying debris as large as locomotives. The flood all but wiped out Johnstown, located 14 miles downstream, leaving over 2,200 dead. 46 years later, floods once again brought disaster to Johnstown. Race through the streets of Johnstown. The Stony Creek and the Little Panama ran wild and poured their waters into the downtown area. But damage in 36 was $41 million, a devastating blow to Johnstown. But this time, the people of Johnstown bowed their city would not be wiped out again. Two disasters. But it did happen again, despite best efforts to contain the river. In July of 1977, torrential rains dumped as much as 12 inches of rainfall in eight hours around Johnstown. Channel improvements resulted in flood depths that were less than those of 1936. However, the result was worse, with 78 deaths and damages in excess of $200 million. Given the awesome power that flood waters represent, why would anyone choose to live next to a river and potential catastrophe? Well, many people do, and for lots of reasons. Recreation, scenic beauty, availability of land. And who knows, maybe just out of plain ignorance. Maybe they just didn't know it could flood here. The first rule about building in the flood plain is don't do it if you don't have to. The best way to avoid the hazards of a flood area is to avoid building in flood prone areas. But seeing as how people will build and live just about anywhere, what is the best way to build a house to help improve its chances of surviving the next flood? There are several considerations that need to be addressed if you build in the flood plain. This is because no two sites and no two rivers are the same, and the specific characteristics of each will determine the type of construction techniques you use. And the most important of these considerations are the flood characteristics found at the building site. And the most obvious of these characteristics is the depth that flooding can reasonably be expected to reach. For larger rivers, this flood depth can be quite significant. Since flood depths vary from storm to storm, a standard flood elevation that can reasonably be expected to occur is normally used. This is the flood elevation that has a 1% chance of occurring in any given year. This figure is sometimes called the 100-year flood, but it's more properly known as the base flood elevation. The reason why you need the base flood elevation is simple. It tells you how high you need to elevate your house in order to give it a reasonable chance of staying above floodwaters. The reason why you elevate your house is equally simple. Normal construction cannot withstand the force that even low levels of flooding will exert against the structure. The weight of these floodwaters can quickly destroy even the best-built home. The flood depth is not the only characteristic that needs to be considered. An equally important characteristic is the potential velocity of the flood water. As you can see here, fast-moving floodwaters can cause extensive damage to anything that happens to be in the way. This is because the velocity of the water translates into a force that can quickly overwhelm any structure in its path. While it may not be possible to determine the exact flood velocities for a particular site, it is a good idea to try to find out if your location may be subject to high-velocity floodwaters. While there are no set guidelines, we generally agreed that potential flood velocities of 5 feet per second or more are considered high and may require special building techniques. In severe cases, the cost of building to withstand these forces may not be practical. Your local building official may be able to help you make this determination. While depth and velocity are the two most important flood characteristics, there are several others that should be considered. These include the duration of flooding, the potential for debris, such as ice and trees, and sufficient warning time to allow for evacuation to higher ground. Another set of characteristics that should be examined are those of the building site. The type of soil may play a role in determining what type of building foundation can be used. For instance, sandy or loose soil is more prone to erosion during flooding. Its presence may require the use of a column or post foundation instead of a slab foundation. Speaking of foundations, remember that the National Flood Insurance Program requirements prohibit the use of basement foundations in the floodplain, since basements are more prone to flood damage. Another site characteristic is that rivers are constantly eroding soil as a natural process. Even if your site is above the floodplain, it may not be immune to the effects of erosion. One final consideration is that your building site may contain features that can be used to help reduce potential flood damage. An example might be a small rise in elevation that could deflect some of the flood water's velocity. The important point here is to evaluate your building site and use it to its best potential to help better protect your home. Well, since the storm has moved into the area, this would be a good chance to recap what we've covered so far. Every site within the floodplain has several specific characteristics that should be examined before we plan to build. These include the base flood elevation, the flood velocities, the flood duration, the debris potential, the warning time, the soil conditions, the erosion potential, and the general topography. Well, enough site work. Let's take a ride into town. There's somebody we need to talk to before we go any further. What we've been trying to show you so far is that every site in the floodplain is unique. And this is because each of these characteristics we've been talking about will vary from place to place. You may be building in a floodplain with low flood depths and low velocities. This will require only minor elevation on almost any type of foundation. Or you may be located in a hilly area near a small river. This site will probably have low flood depths but high velocities. Here erosion is a big concern and may limit the types of foundations that can be used. Near larger rivers, the conditions may be such that you'll be dealing with deep flood depths with low velocities. Typically, people will elevate a structure of full storage to use the lower area for parking or limited storage. And this will play a role in what type of foundation and construction is used. The final set of considerations would be near a large, fast-moving river. Here the deep flood depths and the high velocities will make construction difficult, if not impossible. Add in the other considerations we've discussed and one can put together endless combinations of flood and site variables. A lot of good questions that are going to require even better answers if a home is going to have any chance of withstanding any type of flood. Which is why the first step to take after choosing a prospective building site is to visit your local building official who should be able to answer most of your questions or give you the resources you need to answer them yourself. Karen, Kevin Murray, we spoke on the phone. Hi, Kevin, how are you? Fine, thanks. Listen, I have several prospective building sites in mind and I'm pretty sure they're in the flood plain. What do I have to do? Okay, first let's check the map. Ah, yes, I know what this is. It's our flood insurance rate map, otherwise known as Firm. My sites are located upstream of this river, here in this A zone. And here's the base flood elevation that I have to build my house to. Right. What's this area here by the river? Okay, now that's the floodway. Unfortunately our city ordinance is required that no building go on there basically because it will increase flood levels. Oh, let's see here. Well, that's no problem. My sites are outside the floodway. Okay. Okay, now I know my sites are in the flood plain. I know the base flood elevation, which is the elevation my house must be built to. What else do I need to know? Okay, you'll also need to know the great elevations. Check here at City Hall first. If we can't provide that, check with your local surveying company. Basically what you'll be doing there is subtracting that elevation from your flood elevation. That will tell you how many feet above street level you'll have to be building on. I see. And what do I need in order to get a building permit? For a building permit, you'll need to fill out a project checklist, a building permit application, an elevation certificate, and I've also enclosed a copy of our ordinances that you'll also have to comply with. Okay, well, it sounds like I've got everything I need here. Thanks so much for your time. If you have any questions, give me a call. I'll do that. Thanks, Kevin. Bye-bye. As part of any community's participation in the National Flood Insurance Program, the Federal Emergency Management Agency provides a flood insurance rate map or FIRM. It's on this FIRM that the base flood elevations are indicated. In addition to the base flood elevation, for most rivers, a floodway may also be indicated. This will either be directly on the FIRM or for older maps on a separate flood boundary and floodway map. The floodway is the area that contains the river and enough of the surrounding flood plain to allow floodwaters to pass without increasing flood heights by more than one foot. In other words, if all the land outside the floodway were to be filled in, flood heights within the remaining floodway increased by only one foot. In order to maintain the floodway, communities cannot allow any new development that will increase flood elevations by any amount. Other sources of information can be found in reports issued by the Tennessee Valley Authority, the Corps of Engineers, and the Soil Conservation Service. Communities that participate in the National Flood Insurance Program require, among other things, that any new or substantially improved construction located in the flood plain have its lowest floor elevated to or above the base flood elevation. Before you build, your best bet is to contact your local building official and find out what the base flood elevation is for your site and what the exact building requirements are for elevating your structure above this level. And you'll send me some information about the state regulations and the soil surveys. Great, thanks a lot. That was the state agency responsible for enforcing the flood plain management regulations. They may be a good source for data on the area you want to build in. So I'm up to date on flood conditions, which means I'm ready to start building, or at least I'm ready to start planning to build. Dan Akerty, a good friend with the Pennsylvania Department of Community Affairs, has agreed to give me a guided tour of the area first thing in the morning. That'll give us a chance to go out and look at some completed homes and see some construction techniques that can be used to address the flood and site concerns that we've covered. Dan, I appreciate the tour. No problem, Kevin. So what are we looking at here? This house is in the flood plain of the creek directly behind us here. The base flood elevation here is about three feet above ground level. Looking at this house, I'd say this is an example of elevation on fill, certainly higher than the rest of the houses on the street. Yes, it is, but let's get a better vantage point. All right. The builder of this home elected to place the house on a fill pad, in essence raising the ground elevation above the base flood elevation. Well, what are the limitations to using this technique? Well, this can only be used effectively up to about three to four feet in elevation. That's not a problem for this particular site. What about erosion? Erosion can be a problem if you have velocity floodwaters. We don't here, but it's still a good idea to keep the pad properly planted. Well, they've certainly done that. Well, let's move on. Shall we? Sure. I take it this house is in the flood plain of that river, located behind those trees over there. That's right, Kevin. This is pretty much a backwater area here. There aren't any velocities associated with the flooding, and the base flood elevation is only three feet above ground level. Let's go take a closer look. Okay. Now, what type of elevation technique are we looking at here? Well, Kevin, if you take a look at this house, you can tell that the owner of the structure has elevated it on these solid concrete block foundation walls. The walls themselves are tied into footers that are sufficient size and depth to withstand any flood forces that may be exerted upon them. That's a pretty common technique here in this part of the country. Now, what about these openings here in the foundation wall? Do they serve a purpose? Yeah, they sure do. All that they do is allow floodwaters to enter and to exit at the same rate as it does outside the structure. It equalizes the pressure that keeps these walls from collapsing. I see. Now, I'm presuming the building utilities have been elevated to the level of the lowest floor to protect them from flood damage. Yes, that's correct. You know, I know another site that has more severe flood problems than this one. What do you say we're going to take a look? Thank you. That's a good-sized river. I imagine the flood conditions here are pretty severe. They certainly are. In fact, this site is subject to significant flood depths and velocities. What did the builder do here, Dan? Well, Kevin, this house only had to be constructed about five feet above grade. The builder chose instead to elevate a full story, thereby creating an area below that can be used for garage or for storage. What was done about the high flood velocities? Well, there are garage doors at either end of this structure. In times of flooding, they can be raised. It allows the floodwaters to pass below and it doesn't cause any damage. Oh, that's very clever. And judging by the mark on the wall here, it looks like the owners had a chance to test this out at some point. Yes, they did. In fact, it worked. Was that Hurricane Eloise? Yes, it was. It was always in 1975. It caused a lot of damage in the area. But not to this house? Not to this house. This site is located along the banks of the river. The base flood elevation at this point is about six feet above grade and there are velocities associated with the floodwaters. So this is our example of elevation on columns. It sure is. Reinforce concrete block columns. It's the only feasible method for constructing the flood elevations of this height. What are some of the advantages to using this method? Well, this method allows floodwaters to pass safely beneath the building. It doesn't act as a dam for debris, and it protects the integrity of the structure. Now, erosion usually accompanies high-velocity floodwaters. What was done about that for this house? Well, this site has very good soils. We were able to get the footers deep enough to guard against erosion, so it really hasn't been a problem. I see. Now, if this had not been the case and the soil was loose enough to be subject to erosion, then a different type of foundation, such as one made up of wood pilings would have been called for. The advantage of wood pilings is that they can be deep enough to resist extensive erosion. It's for this reason that they're normally found in sandy coastal areas, as we saw in our first show. Now, what did the folks here choose to do about their utilities? Well, the utilities at this house have been placed at the first floor elevation. It protects them against flooding. I see. Well, this is a very good example, Dad. Kevin, it's been my pleasure. Have you ever been fishing around here? No, I never have. Have you ever been fishing here? There's great fishing. At the end of our first show, we briefly talked about the advantages of following the construction guidelines of the National Flood Insurance Program. Those advantages pertain to coastal zones, but they apply just as well to riverine areas. There are two primary advantages. First, the result of following these guidelines is a structure that is better able to resist potential flood damage. And second, the flood insurance rates will be more affordable. Now, this is just as important, because flood insurance is an important part of home flood protection. Why? Because no matter how well or how high you build your home, there's still a chance it can be flooded. Insurance is your protection against that flood. But let's listen to what these people have to say. Well, you have to build according to standard to get a permit, number one. And number two, the advantage to the consumer, and for me as the builder trying to sell, is that the consumer is going to be able to get a better right on their home. Well, along came the 77 flood and damaged my home inside, cracked the walls in the basement. All the ground was gone and the garage sagged. And now I know why I should keep up my flood insurance. Since then, I've been painted very faithfully and I'm going to continue. Because of the National Flood Insurance Program, our state laws and local flood play management regulations. And our awareness on the part of the general public really beginning to see the kind of construction that's going to make a real difference in reducing flood losses in the future. We hope that we've shown you that building in the riverine flood plane can be a dangerous undertaking. One that should be avoided if at all possible. But if you must build, remember there are several considerations that need to be examined before you begin. While some of them may seem trivial, and each one will play a role in the construction methods you use to build a more flood resistant home. To recap, learn about the flood characteristics of your site. The flood depth, the flood velocity, the flood duration, the potential for debris and the warning time. Learn about the site characteristics, the soil conditions, the potential for erosion and the general topography. Consult your local building official. Obtain the flood insurance rate map and determine what the base flood elevation is for your site. Decide what type of building foundation is best for your flood and site characteristics. And finally, determine what types of construction methods and materials, including protecting the building's utilities, are best for your situation. Now as I said at the top of the show, the best way to avoid flood losses is not to build in the flood plain. But if you must, know your site. And more importantly, know your flood. On our next show, we're going to look at some construction and remodeling techniques that will help protect an existing home from flood damage. And if this weather keeps up, the kind of information just might come in handy. I'm Kevin Murray and I'll see you next time on Best Build.