private double[][] wettedArea( double[] waterLevel, List<RiverPoint> riverPoints ) {
        /* right and left limits of the main channel */
        double dx, sx;
        double area_b, base_dx, base_sx, altezza;
        double peri_b;
        double larghe_b;
        double gau_b;
        double alfa_num, alfa_den;
        /* *_loc refer to the local slice (trapezoidal) of the area of the section */
        double area_loc, peri_loc, gau_loc;

        int imax = riverPoints.size();
        double[][] tirase = new double[imax][6];

        /*
         * Calculate: wetted area, wetted perimeter, width of the water surface, the roughness
         * and the alpha coefficient of Coriolis in the section i
         */
        for( int i = 0; i < imax; i++ ) {

            RiverPoint section = riverPoints.get(i);
            area_b = 0;
            peri_b = 0;
            larghe_b = 0;
            gau_b = 0;
            gau_loc = 0;
            alfa_num = 0;
            alfa_den = 0;

            dx = section.getStartNodeIndex() + 1;
            sx = section.getEndNodeIndex() - 1;

            Coordinate[] sectionCoordinates = section.getSectionCoordinates();
            List<Double> sectionProgressives = section.getSectionProgressive();
            double sectionGauklerStrickler = section.getSectionGauklerStrickler();

            for( int j = (int) dx - 1; j < sx - 1; j++ ) {
                /* Check the segments between the stations j and j+1 of the current section
                 
                // if (section.getYAt(j) >= tirante[i] && section.getYAt(j + 1) >= tirante[i]) {
                // area_b = area_b + 0;
                // peri_b = peri_b + 0;
                // larghe_b = larghe_b + 0;
                // gau_b = gau_b + 0;
                // alfa_num = alfa_num + 0;
                // alfa_den = alfa_den + 0;
                // }
                /* 
                 * case 1: only partially wetted (right side dry) 
                 */

                if (sectionCoordinates[j].z >= waterLevel[i] && sectionCoordinates[j + 1].z < waterLevel[i]) {
                    /* the area of the triangle */
                    base_dx = 0;
                    base_sx = waterLevel[i] - sectionCoordinates[j + 1].z;
                    altezza = base_sx * (sectionProgressives.get(j + 1) - sectionProgressives.get(j))
                            / (sectionCoordinates[j].z - sectionCoordinates[j + 1].z);
                    area_b = area_b + (base_dx + base_sx) * altezza / 2.0;
                    /* the part of the bottom that is wetted */
                    peri_b = peri_b + Math.sqrt(Math.abs(base_dx - base_sx) * Math.abs(base_dx - base_sx) + altezza * altezza);
                    /* the width of the water surface */
                    larghe_b = larghe_b + altezza;
                    /* the roughness coefficient */
                    gau_b = gau_b + (sectionGauklerStrickler * Math.pow((base_dx + base_sx) / 2.0, (5.0 / 3.0)) * altezza);
                    gau_loc = sectionGauklerStrickler;
                    /* the alpha coefficient of Coriolis */
                    area_loc = (base_dx + base_sx) * altezza / 2.0;
                    peri_loc = Math.sqrt((base_dx - base_sx) * (base_dx - base_sx) + altezza * altezza);
                    if (area_loc != 0) {
                        // use the method of Einstein-Horton?
                        alfa_num = alfa_num
                                + (gau_loc * gau_loc) * Math.pow(area_loc, (7.0 / 3.0)) / Math.pow(peri_loc, (4.0 / 3.0));
                    }
                    alfa_den = alfa_den + gau_loc * area_loc * Math.pow(peri_loc, (2.0 / 3.0));

                    /* no one of these values can be null */
                    /*
                     * if ( base_dx<0 || base_sx<0 || altezza<0 ) { print("POSIZIONE " + i " -
                     * TIRANTE " + waterLevel[i] + "Error in the evaluation of the wetted area"};
                     */
                }
                /* case 2: only partially wetted (left side dry) */

                if (sectionCoordinates[j + 1].z >= waterLevel[i] && sectionCoordinates[j].z < waterLevel[i]) {
                    /* the area of the triangle */
                    base_sx = 0;
                    base_dx = waterLevel[i] - sectionCoordinates[j].z;
                    altezza = base_dx * (sectionProgressives.get(j + 1) - sectionProgressives.get(j))
                            / (sectionCoordinates[j + 1].z - sectionCoordinates[j].z);
                    area_b = area_b + (base_dx + base_sx) * altezza / 2.0;
                    /* the part of the bottom that is wetted */
                    peri_b = peri_b + Math.sqrt(Math.abs(base_dx - base_sx) * Math.abs(base_dx - base_sx) + altezza * altezza);
                    /* the width of the water surface */
                    larghe_b = larghe_b + altezza;
                    /* the roughness coefficient */
                    gau_b = gau_b + (sectionGauklerStrickler * Math.pow((base_dx + base_sx) / 2.0, (5.0 / 3.0)) * altezza);
                    gau_loc = sectionGauklerStrickler;

                    /* the alpha coefficient of Coriolis */
                    area_loc = (base_dx + base_sx) * altezza / 2.0;
                    peri_loc = Math.sqrt((base_dx - base_sx) * (base_dx - base_sx) + altezza * altezza);
                    if (area_loc != 0) {
                        alfa_num = alfa_num
                                + (gau_loc * gau_loc) * Math.pow(area_loc, (7.0 / 3.0)) / Math.pow(peri_loc, (4.0 / 3.0));
                    }
                    alfa_den = alfa_den + gau_loc * area_loc * Math.pow(peri_loc, (2.0 / 3.0));

                    /* no one of these values can be null */
                    /*
                     * if ( base_dx<0 || base_sx<0 || altezza<0 ) { print("POSIZIONE " + i " -
                     * TIRANTE " + waterLevel[i] + "Error in the evaluation of the wetted area"};
                     */

                }
                /* case 3: completely wetted */

                if (sectionCoordinates[j + 1].z < waterLevel[i] && sectionCoordinates[j].z < waterLevel[i]) {
                    base_dx = waterLevel[i] - sectionCoordinates[j].z;
                    base_sx = waterLevel[i] - sectionCoordinates[j + 1].z;
                    altezza = sectionProgressives.get(j + 1) - sectionProgressives.get(j);
                    area_b = area_b + (base_dx + base_sx) * altezza / 2.0;

                    peri_b = peri_b + Math.sqrt(Math.abs(base_dx - base_sx) * Math.abs(base_dx - base_sx) + altezza * altezza);
                    larghe_b = larghe_b + altezza;
                    gau_b = gau_b + (sectionGauklerStrickler * Math.pow((base_dx + base_sx) / 2, (5.0 / 3.0)) * altezza);
                    gau_loc = sectionGauklerStrickler;

                    area_loc = (base_dx + base_sx) * altezza / 2;
                    peri_loc = Math.sqrt((base_dx - base_sx) * (base_dx - base_sx) + altezza * altezza);
                    if (area_loc != 0) {
                        alfa_num = alfa_num
                                + (gau_loc * gau_loc) * Math.pow(area_loc, (7.0 / 3.0)) / Math.pow(peri_loc, (4.0 / 3.0));
                    } else {
                        alfa_num = alfa_num + 0;
                    }
                    alfa_den = alfa_den + gau_loc * area_loc * Math.pow(peri_loc, (2.0 / 3.0));

                    /* no one of these values can be null */
                    /*
                     * if ( base_dx<0 || base_sx<0 || altezza<0 ) { print("POSIZIONE " + i " -
                     * TIRANTE " + waterLevel[i] + "Error in the evaluation of the wetted area"};
                     */
                }
            }
            /*
             * Fill the final matrix tirase
             */
            /* wetted area */
            tirase[i][0] = area_b;
            /* wetted perimeter */
            tirase[i][1] = peri_b;
            /* hydraulic radius */
            tirase[i][2] = area_b / peri_b;
            /* width of the water surface */
            tirase[i][3] = larghe_b;
            /* roughness coefficient */
            gau_b = gau_b / (area_b * Math.pow((area_b / peri_b), (2.0 / 3.0)));

            tirase[i][4] = gau_b;
            /* alpha coefficient of Coriolis */
            tirase[i][5] = alfa_num / (area_b * Math.pow(gau_b, 2) * Math.pow((area_b / peri_b), (4.0 / 3.0)));
            /* tirase[i][6]=1; */
            /* tirase[i][6]=area_b*alfa_num/(alfa_den*alfa_den); */
        }

        return tirase;
    }
private double [ ] [ ] wettedArea ( double [ ] waterLevel , List < RiverPoint > riverPoints ) { double dx , sx ; double area_b , base_dx , base_sx , altezza ; double peri_b ; double larghe_b ; double gau_b ; double alfa_num , alfa_den ; double area_loc , peri_loc , gau_loc ; int imax = riverPoints . size ( ) ; double [ ] [ ] tirase = new double [ imax ] [ 6 ] ; for ( int i = 0 ; i < imax ; i ++ ) { RiverPoint section = riverPoints . get ( i ) ; area_b = 0 ; peri_b = 0 ; larghe_b = 0 ; gau_b = 0 ; gau_loc = 0 ; alfa_num = 0 ; alfa_den = 0 ; dx = section . getStartNodeIndex ( ) + 1 ; sx = section . getEndNodeIndex ( ) - 1 ; Coordinate [ ] sectionCoordinates = section . getSectionCoordinates ( ) ; List < Double > sectionProgressives = section . getSectionProgressive ( ) ; double sectionGauklerStrickler = section . getSectionGauklerStrickler ( ) ; for ( int j = ( int ) dx - 1 ; j < sx - 1 ; j ++ ) { if ( sectionCoordinates [ j ] . z >= waterLevel [ i ] && sectionCoordinates [ j + 1 ] . z < waterLevel [ i ] ) { base_dx = 0 ; base_sx = waterLevel [ i ] - sectionCoordinates [ j + 1 ] . z ; altezza = base_sx * ( sectionProgressives . get ( j + 1 ) - sectionProgressives . get ( j ) ) / ( sectionCoordinates [ j ] . z - sectionCoordinates [ j + 1 ] . z ) ; area_b = area_b + ( base_dx + base_sx ) * altezza / 2.0 ; peri_b = peri_b + Math . sqrt ( Math . abs ( base_dx - base_sx ) * Math . abs ( base_dx - base_sx ) + altezza * altezza ) ; larghe_b = larghe_b + altezza ; gau_b = gau_b + ( sectionGauklerStrickler * Math . pow ( ( base_dx + base_sx ) / 2.0 , ( 5.0 / 3.0 ) ) * altezza ) ; gau_loc = sectionGauklerStrickler ; area_loc = ( base_dx + base_sx ) * altezza / 2.0 ; peri_loc = Math . sqrt ( ( base_dx - base_sx ) * ( base_dx - base_sx ) + altezza * altezza ) ; if ( area_loc != 0 ) { alfa_num = alfa_num + ( gau_loc * gau_loc ) * Math . pow ( area_loc , ( 7.0 / 3.0 ) ) / Math . pow ( peri_loc , ( 4.0 / 3.0 ) ) ; } alfa_den = alfa_den + gau_loc * area_loc * Math . pow ( peri_loc , ( 2.0 / 3.0 ) ) ; } if ( sectionCoordinates [ j + 1 ] . z >= waterLevel [ i ] && sectionCoordinates [ j ] . z < waterLevel [ i ] ) { base_sx = 0 ; base_dx = waterLevel [ i ] - sectionCoordinates [ j ] . z ; altezza = base_dx * ( sectionProgressives . get ( j + 1 ) - sectionProgressives . get ( j ) ) / ( sectionCoordinates [ j + 1 ] . z - sectionCoordinates [ j ] . z ) ; area_b = area_b + ( base_dx + base_sx ) * altezza / 2.0 ; peri_b = peri_b + Math . sqrt ( Math . abs ( base_dx - base_sx ) * Math . abs ( base_dx - base_sx ) + altezza * altezza ) ; larghe_b = larghe_b + altezza ; gau_b = gau_b + ( sectionGauklerStrickler * Math . pow ( ( base_dx + base_sx ) / 2.0 , ( 5.0 / 3.0 ) ) * altezza ) ; gau_loc = sectionGauklerStrickler ; area_loc = ( base_dx + base_sx ) * altezza / 2.0 ; peri_loc = Math . sqrt ( ( base_dx - base_sx ) * ( base_dx - base_sx ) + altezza * altezza ) ; if ( area_loc != 0 ) { alfa_num = alfa_num + ( gau_loc * gau_loc ) * Math . pow ( area_loc , ( 7.0 / 3.0 ) ) / Math . pow ( peri_loc , ( 4.0 / 3.0 ) ) ; } alfa_den = alfa_den + gau_loc * area_loc * Math . pow ( peri_loc , ( 2.0 / 3.0 ) ) ; } if ( sectionCoordinates [ j + 1 ] . z < waterLevel [ i ] && sectionCoordinates [ j ] . z < waterLevel [ i ] ) { base_dx = waterLevel [ i ] - sectionCoordinates [ j ] . z ; base_sx = waterLevel [ i ] - sectionCoordinates [ j + 1 ] . z ; altezza = sectionProgressives . get ( j + 1 ) - sectionProgressives . get ( j ) ; area_b = area_b + ( base_dx + base_sx ) * altezza / 2.0 ; peri_b = peri_b + Math . sqrt ( Math . abs ( base_dx - base_sx ) * Math . abs ( base_dx - base_sx ) + altezza * altezza ) ; larghe_b = larghe_b + altezza ; gau_b = gau_b + ( sectionGauklerStrickler * Math . pow ( ( base_dx + base_sx ) / 2 , ( 5.0 / 3.0 ) ) * altezza ) ; gau_loc = sectionGauklerStrickler ; area_loc = ( base_dx + base_sx ) * altezza / 2 ; peri_loc = Math . sqrt ( ( base_dx - base_sx ) * ( base_dx - base_sx ) + altezza * altezza ) ; if ( area_loc != 0 ) { alfa_num = alfa_num + ( gau_loc * gau_loc ) * Math . pow ( area_loc , ( 7.0 / 3.0 ) ) / Math . pow ( peri_loc , ( 4.0 / 3.0 ) ) ; } else { alfa_num = alfa_num + 0 ; } alfa_den = alfa_den + gau_loc * area_loc * Math . pow ( peri_loc , ( 2.0 / 3.0 ) ) ; } } tirase [ i ] [ 0 ] = area_b ; tirase [ i ] [ 1 ] = peri_b ; tirase [ i ] [ 2 ] = area_b / peri_b ; tirase [ i ] [ 3 ] = larghe_b ; gau_b = gau_b / ( area_b * Math . pow ( ( area_b / peri_b ) , ( 2.0 / 3.0 ) ) ) ; tirase [ i ] [ 4 ] = gau_b ; tirase [ i ] [ 5 ] = alfa_num / ( area_b * Math . pow ( gau_b , 2 ) * Math . pow ( ( area_b / peri_b ) , ( 4.0 / 3.0 ) ) ) ; } return tirase ; }
<p>
This method calculates
</p>
<ul>
<li> wetted area </li>
<li> wetted perimeter </li>
<li> hydraulic radius </li>
<li> width of water surface </li>
<li> roughness </li>
<li> alpha coefficient of Coriolis </li>
</ul>
in each section starting from the water depth.
<p>
The method returns a matrix with:
<ul>
<li> rows: the sections </li>
<li> cols: the variables above. </li>
</ul>
</p>
The method calculates
<p>
<b>wetted area</b> calculated as the sum of the trapezoids obtained by tracing a vertical
line starting from each points of the sections; each trapezoid has a base
on the right (base_dx) and a base on the left (base_sx) and an height (altezza).
<b>wetted perimeter</b> as the sum of all the wetted segments of the river ground
<b>hydraulic radius</b> using the definition formula
<b>width of water surface</b> height of the trapezoids defined to calculate the wetted area
<b>roughness coefficient</b> using the Engelund method: the section is divided into trapezoids
as for the wetted area and for each trapezoid this quantity is calculated:
<b>Ks(j)*Y(j)^(5/3)*B(j)</b> where:
</p>
<ul>
<li><b>Ks(j)</b> Gaukler-Strickler coefficient for the segment j</li>
<li><b>Y(j)</b> water depth for the trapezoid j obtained as the ratio between the
area and the width of the water surface for each trapezoid </li>
<li><b>B(j)</b> is the width of the water surface of the trapezoid j</li>
</ul>
<p>
NOTE: the hydraulic radius of the trapezoid j is approximated with the water depth even if this
is recommended only with large sections.
</p>
<p>
The <b>roughness coefficient</b> is obtained dividing the sum of all the quantities
with <b>(A*RH^(2/3))</b>, where A is the total wetted area and RH the hydraulic radius
referred to the whole section.
</p>
<p>
<b>The alpha coefficient of Coriolis</b> is calculated using the same subdivision of the
section used for the calculation of the wetted area and for each trapezoid this quantity
is evaluated:
<b>Ks(j)^2*A(j)^(7/3)/P(j)^(4/3)</b> where:
</p>
<ul>
<li><b>Ks(j)</b> the Gaukler-Strickler coefficient for the segment j</li>
<li><b>A(j)</b> the area of the trapezoid j</li>
<li><b>P(j)</b> the wetted perimeter of the trapezoid j</li>
</ul>
<p>
This is then calculated by dividing the sum of all the quantities for
<b>(ATOT*KsTOT^2*RHTOT^(4/3))</b> where:
<ul>
<li>ATOT the area of the whole section</li>
<li>KsTOT the roughness total coefficient  </li>
<li>RHTOT the hydraulic radius of the whole section</li>
</ul>
</p>

@param waterLevel il vettore dei tiranti
@param riverPoints il vettore che contiene le sezioni di calcolo
@return una matrice che ha come elementi di ogni colonna della i-esima riga le
grandezze:
- wetted area
- wetted perimeter
- hydraulic radius
- roughness
- alpha coefficient of Corilis
relative alla i-esima sezione.