Latest Contributions by NguyenMinh_Huyen

hi Mark, Thanks alot... it worked perfectly, the small raster now has the same extent as the big one and I can continue with the raster calculator now..I have a lot to do so I haven't managed time to go back to "the line" in the ArcHydro yet but I will, in several days, then I'll get back to you. Thanks ^^ ... View more

Hi Mark, I also tried to burn a stream over the bridge in ArcHydro. First I created a shape file of a stream then --> Terrain Processing-->DEM Manipulation-->DEM Reconditioning..then I got the Agree DEM but there's definitely sth wrong with my AgreeDEM, it's just the line...I thought I should have obtained a DEM with a stream line within it? ... View more

Arc Hydro tools simply convert the polyline to a raster with a value. The value can be very big. You can make the value a little more than you need to "burn" a stream into the embankment. Then, Arc Hydro subtracts the polyline value from the dem. The fill sinks function fills in the stream to allow the flow direction to go downstream. You can do this without Arc Hydro. Draw a "stream" polyline through the embankment with the ends of the polyline where the low points are in the stream up and down stream of the embankment. Convert the stream to a raster with a high value, high enough the go below the embankment. (You may need to create a field in the polyline table for this value). Then, with with raster math, subtract your stream raster from the dem. After this, you use the resulting dem with the fill function and move on from there like you did before. Arc Hydro will make the "burned stream" more than one cell wide. You may need to do that, though I'd try doing it with whatever results the polyline to raster conversion give you. Seem like it should work. "Then, with with raster math, subtract your stream raster from the dem." Could you explain to me in more details this step? I tried with raster calculator but I didn't get the right resulting DEM? which tool exactly should I use to do this "subtract"? Thanks a lot. ... View more

You have to process the dem. There are tools in Arc Hydro that do this. The tools let you "burn" a stream through the road embankment so the area behind the embankment is not filled during the fill sinks process. I've posted several Arc Hydro helps in the link below my signature. Thanks Mark! It's quite a lot of information for me as I've never used ArcHydro before..and I really need to my stuff as soon as possible!So is there any other tools? I mean I just want to modify the DEM, to get rid of the road over the river, to make a new DEM without the culvert system, is that possible? I don't know yet if I'm gonna run the flow accumulation after but I need a new DEM without that road for other purposes.  I'm thinking of making a polygon shape file over the road, add a new "elevation field" for that polygon (the elevation value = elev of road - elev of the river) then convert it to raster then use raster calculator (new DEM = DEM - raster polygon) to make a new DEM...is that correct? it sounds a little bit ..weird..i'm not sure... ... View more

Hi Stuart, Thanks a lot 🙂 I've successfully downloaded and installed ArcHydro! ... View more

Hi, I tried to download but I've encountered this problem: "Duplicate headers received from server The response from the server contained duplicate headers. This problem is generally the result of a misconfigured website or proxy. Only the website or proxy administrator can fix this issue. Error 349 (net::ERR_RESPONSE_HEADERS_MULTIPLE_CONTENT_DISPOSITION): Multiple distinct Content-Disposition headers received. This is disallowed to protect against HTTP response splitting attacks." Does anyone know how to fix it? Thanks in advance ... View more

I cant provide you with examples as that would require client release forms, but I can help get you started on your own.  You are both lucky and unlucky.  Projects like this are already done for a number of reasons and a similar system is being included in FEMA's new RISK MAP program.  Does it have to be a coastal area?  That greatly complicates modeling(which is the unlucky part).  When you are dealing with coastal areas they are generally divided into relatively short stretches and a flood elevation is developed for just that section. Due to the wave runup, areas that are next to each other may have different flood elevations during the same storm event.  HEC-RAS is a River Analysis System and does not do coastal flooding.  There are models out there that do that, but being located in middle america I havent had to use one yet. You are lucky though in that USGS has gages on rivers and NOAA has coastal gages (http://tidesandcurrents.noaa.gov/) that provide elevation and discharge data over time.  Included in the gage data are historical storms, ie hurricane Floyd hitting the Carolinas was captured by some gages so you can watch the storm surge come in and recede which is basically what you need).This would negate having to develop a flood model(unless its a requirement of your masters program) Data needs: topography-either contours or a digital elevation model(DEM) for the area of interest water surface elevations-grab a gage and get some elevation data Tools: ArcGIS 3dAnalyst extension Possibly Spatial Analyst Process 1) Create a polyline shapefile and draw lines describing the area you think your gage data is accurate for and assign the appropriate elevations(since you want multiple gage events create an attribute field for each event). 2) using 3dAnalyst convert your polyline file to a TIN (3dAnalyst Toolbar->Create/Modify TIN select your polyline file, assign the output location, identify the elevation source, all else leave at default) 3)convert your topography to a TIN   3a) if contours, do it the same way you did the polyline elevation file   3b)if a DEM use 3dAnalyst toolbar-> Convert->Raster to TIN  (keep the Z value as low as possible) 4) If you just want a polygon to show the extents of the flooding use "TIN difference" which is located in the 3d Analyst Tools Toolbox under "Tin surface" 5) if you want a raster that shows the depths at each location convert your Terrain and Water Surface TINs to Rasters (3dAnalyst toolbar->Convert-Tin to Raster) and use Raster Calculator in the Spatial Analyst toolbar to subtract your terrain data from the water surface raster. If you have any questions or need something explained more let me know and I'll do what I can.  Good luck with your masters degree. Hi Matt, I have quite the same problem. I have a DEM of the interested area, a vector layer of land use and of course a specific height of water level Can I solve the problem just by using the Raster Calculator in the Spatial Analyst tools to visualize which area will be flooded with that specific height of water, then merge it with the land use to calculate the surface area of the flooded area. Is it correct? and Would it be more simple doing this way? Thanks in advance! ... View more