[Tex/LaTex] horizontal line width using \xhline

tables

So I've been using \Xhline in my tables so that I can set the top, second and bottom line of the tables thicker than the rest. My code (below) works and produces a table and the top and bottom lines have increased in thickness but for some reason the second hasn't even though I've used the exact same command. The code beneath is just for my table, the rest of the document is huge. When I copy this section of code into a new window and run it the table looks perfect, but when I run it in my main document the line thickness doesn't always increase. Does anyone know what might be causing it to intermittently work in my document?

p.s couldn't tag xhline or hline hence only including the table tag.

\documentclass[11pt,a4paper]{report}
\usepackage {multirow}
\usepackage [english]{babel}
\usepackage{fixltx2e}
\usepackage{setspace}
\usepackage{booktabs}
\usepackage{array}
\usepackage{tabularx}
\usepackage{calc}
\usepackage{makecell}

\begin{document}

\begin{table}[!ht]
\centering
\setlength\extrarowheight{5pt}
\begin{tabular}{p{3cm}p{3cm}p{8.5cm}}
\Xhline{2.0pt}
\multicolumn{3}{c}{\textbf{Model set-up}} \\
\Xhline{2.0pt}
\multicolumn{2}{l}{\textbf{Channel dimensions}} & 29.76m x 2m\\ \Xhline{0.2pt}
\multirow{2}{*}{\textbf{Bathymetry}} & 8m$<$x$<$12m & Z\textsubscript{f} = 0.05 * (x - 10) \textsuperscript{2}\\ 
& Everywhere else: & Z\textsubscript{f} = -0.2m \\ \Xhline{0.2pt}
\multicolumn{2}{l}{\textbf{Mesh (Figure XXXX)}} & Triangulated regular grid. Increased resolution at the bump and it is wake. \\ \Xhline{0.2pt}
\multicolumn{2}{l}{\multirow{3}{*}{\textbf{Boundaries}}} 
      & Channel entrance: Open boundary with prescribed discharge ($Q$ = 2m\textsuperscript{3}) \\ 
\multicolumn{2}{l}{} 
      & Channel exit: Open boundary with prescribed water level ($y$=0.4m)\\
\multicolumn{2}{l}{} 
      & Remaining boundaries: Closed \\ \Xhline{0.2pt}
\multicolumn{2}{l}{\textbf{Friction}} & Bottom friction was defined using the Strickler formula and a coefficient of 40 was set. All other sides were frictionless\\ \Xhline{0.2pt}
\multicolumn{2}{l}{\textbf{Time step}} & 0.02 seconds\\ \Xhline{0.2pt}
\multicolumn{2}{l}{\textbf{Duration}} & 100 seconds\\ \Xhline{0.2pt}
\Xhline{2.0pt}
\end{tabular}
\centering
\end {table}

\end {document}

Best Answer

Here is your table with much less packages in use. I left the line thicknesses as wished by you, but defined this rules just with booktabs. Maybe this works for you:

% arara: pdflatex

\documentclass[11pt,a4paper]{report}
\usepackage{multirow, booktabs}
\usepackage{siunitx}

\begin{document}    
    \begin{table}
        \centering
        \begin{tabular}{p{3cm}p{3cm}p{8.5cm}} \toprule[2.0pt]
            \multicolumn{3}{c}{\textbf{Model set-up}} \\ \midrule[2.0pt]
            \multicolumn{2}{l}{\textbf{Channel dimensions}} & $\SI{29.76}{\metre}\times\SI{2}{\metre}$ \\ \midrule[0.2pt]
            \multirow{2}{*}{\textbf{Bathymetry}} & $\SI{8}{\metre}<x<\SI{12}{\metre}$ & $Z_\mathrm{f} = 0.05\cdot(x-10)^2$\\ & Everywhere else: & $Z_\mathrm{f}= \SI{-0.2}{\metre}$ \\ \midrule[0.2pt]
            \multicolumn{2}{l}{\multirow{2}{*}{\textbf{Mesh (Figure XXXX)}}} & Triangulated regular grid. Increased resolution at the bump and it is wake. \\ \midrule[0.2pt]
            \multicolumn{2}{l}{\multirow{5}{*}{\textbf{Boundaries}}} & Channel entrance: Open boundary with prescribed discharge ($Q = \SI{2}{\cubic\metre}$) \\ 
            \multicolumn{2}{l}{} & Channel exit: Open boundary with prescribed water level ($y=\SI{0.4}{\metre}$)\\
            \multicolumn{2}{l}{} & Remaining boundaries: Closed \\ \midrule[0.2pt]
            \multicolumn{2}{l}{\multirow{3}{*}{\textbf{Friction}}} & Bottom friction was defined using the Strickler formula and a coefficient of $40$ was set. All other sides were frictionless\\ \midrule[0.2pt]
            \multicolumn{2}{l}{\textbf{Time step}} & $0.02$ seconds \\ \midrule[0.2pt]
            \multicolumn{2}{l}{\textbf{Duration}} & $100$ seconds \\ \bottomrule[2.0pt]
        \end{tabular}
    \end{table}     
\end{document}

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