Laserfiche WebLink
<br />Chapter 3 Working With HEC-RAS - An Overview <br /> <br />The data associated with HEC-2 options that are not currently supported in <br />HEC-RAS are ignored. This includes: vertical n values; k values; <br />encroachments on ET records (method 1 encroachments on X3 records are <br />supported); cross section interpolation; split flow data; channel improvements; <br />n value calibration; and ice options. This information will be added to the <br />HEC-2 import routine as the options become available in HEC-RAS. <br /> <br />When bridge data are imported, the user must take special care to ensure that <br />the data are correctly representing the bridge. The bridge routines in HEC- <br />RAS are different than HEC-2, and therefore you may have to modify some <br />data and/or enter some additional data. Whenever you import an HEC-2 data <br />set with bridge data, carefully review all the data for each bridge. Chapter 6 <br />of this user's manual describes the required data for bridges in HEC-RAS. <br />Some key differences between HEC-2 and HEC-RAS are as follows: <br /> <br />1. Special Bridge Data Sets <br /> <br />HEC-RAS does not use a trapezoidal approximation for low flow <br />through the bridge opening. The actual bridge opening is used in both <br />the Yamell method and the momentum method. This could be a <br />problem for HEC-2 special bridge data sets that do not include low <br />chord information on the BT data. If you have a data set like this, you <br />will need to modify the bridge deck information after the data has <br />been imported. <br /> <br />Pier information from the SB record is incorporated as a single pier in <br />the HEC- RAS data set. Piers are treated as a separate pieces of data in <br />HEC-RAS. For special bridges that have piers, you may want to <br />change the single pier to multiple piers, depending on what is actually <br />at the bridge. Pier information can be modified using the Pier editor. <br /> <br />2. Normal Bridge Data Sets <br /> <br />Because piers are treated as a separate piece of data in HEC-RAS, they <br />must not be included in the cross section data or the bridge deck. <br />Since it is common to include pier information as part of the cross <br />section or bridge deck in HEC-2, these data will need to be modified. <br />For data sets that have piers, you will need to remove the pier <br />information from the cross section or bridge deck, and then add the <br />information back in using the Pier editor. <br /> <br />3-16 <br />