Two Lakes : Dreams Realized

The following pages show the site plan dimensions for the original construction of the channel. It is the same size as the original channel. Also shown are computations of flow area for 12 cross-sections of the river: four cross-sections above the straightened channel in the original river, four cross sections in the straightened river channel and four cross-sections in the original river channel below the levee system. These cross-sections, taken from the HEC-2 computer model, show that the straightened river channel is of similar size to the original river channel. Also, shown is a map made of the straightened river channel in 1984, five years after the 1979 flood and one year after the 1983 flood. This map shows the straightened channel to be of similar size to the original river channel. From this map it can be seen that the amount of sand moving down the river channel occludes the channel to a size controlled by the energy in the nominal flow of the river and that no matter how large the channel is constructed, it will be restricted by natural sand levees to a width of 250 feet at brink height. Information shown on the map indicates that this will happen within five years time.

The cutoff channel in this 1965 U. S. Army Corp of Engineers sight plan is 150 feet wide at the base and approximately 250 feet wide at the top. This is approximately the same size as the winding river channel that it replaced. This 1965 site plan also shows the ponding reserve for the fairground area. Construction in this area, 10 feet lower than the fairground property has now been developed. This has necessitated pumping to maintain reserve during the spring flood months.

RM286.533		water @	274.5
249.5	248.8	231	235	236	249
100160	100195	100250	100300	100380	100430					WIDTH=	270
	887.25	1903	2075	3120	1600					AREA=	9585

RM286.927		water @	275.7
253	233	230.5	235.3	250
100490	100530	100600	100650	100720						WIDTH=	230
	1308	3076.5	2140	2313.5						AREA=	8838

RM287.33		water @	276.2
255	240.5	235	236	253
101665	101785	101860	101935	101970						WIDTH=	305
	3414	2883.75	3052.5	1109.5						AREA=	10460

RM287.508		water @	277.2
250.4	236.7	232.4	235	246	250.7
102220	102258	102300	102355	102395	102432					WIDTH=	212
	1278.7	1791.3	2392.5	1468	1067.45					AREA=	7998

RM287.82		water @	277.3
250	233	250
101000	101200	101300								WIDTH=	300
	7160	3580								AREA=	10740	CHANNEL

RM288.171		water @	277.8
258.7	241	234	229.7	233	232	234.8	250.7
100805	100842	100850	100870	100930	100950	101000	101033			WIDTH=	228
	1034.15	322.4	919	2787	906	2220	1156.65			AREA=	9345	CHANNEL

RM288.99		water @	278.6
253.6	241	238.8	239	252.7
100775	100790	100800	101005	101033						WIDTH=	258
	469.5	387	8138.5	917						AREA=	9912	CHANNEL

RM289.46		water @	279.2
252.5	240.7	240	241.5	240.8	241.8	252.6
101815	101892	101945	102008	102028	102070	102080				WIDTH=	265
	2510.2	2059.05	2422.35	761	1591.8	320				AREA=	9664	CHANNEL

RM290.08		water @	279.7
271	244	242	243.8	240.5	244	250.8	251.6
102730	102805	102840	102940	103040	103112	103130	103140			WIDTH=	410
	1665	1284.5	3680	3755	2696.4	581.4	285			AREA=	13947

RM290.46		water @	280
263.8	259.2	241.4	237.4	238.8	238.4	244.4	248	248.2	257
102447	102478	102526	102563	102610	102655	102665	102682	102700	102732	WIDTH=	285
	573.5	1425.6	1502.2	1969.3	1863	386	574.6	574.2	876.8	AREA=	9745

RM291.81		water @	280.8
266	244	240
17200	17300	17400								WIDTH=	200
	2580	3880								AREA=	6460

RM292.34		water @	280.9
244	240
14650	15000									WIDTH=	350
	13615									AREA=	13615


							AREA		WIDTH
	AVERAGE OF 4 X-SECTIONS SOUTH OF CHANNEL IS						9220		254
	AVERAGE OF 4 X-SECTIONS IN CHANNEL IS						9915		263
	AVERAGE OF 4 X-SECTIONS NORTH OF CHANNEL IS						10942		311

When the 1979 flood occurred, 90% of the cutoff channel had become restricted to a width at brink height of 250 feet and trees had grown to the bank of the remaining channel.

One half mile of the cutoff channel had been used to dredge 800,000 yards of sand. This operation ended in November, 1978 (prior to the 1979 flood) the sand dredging operation opened up the cutoff channel to a width of 500 feet and deepened it an additional 10 feet in places.

Five years after the dredging operation ended, sand moving down the river channel had refilled much of the dredged area and natural sand levees had formed (see map previous page) again restricting the cutoff channel to a width of 250 feet.

This section of river can be observed today by looking north of the I-55 highway bridge. The dredged area has completely refilled with sand and trees over 10 years old have grown over the entire dredged area except for the 250 foot wide restricted cutoff channel.

Pearl River Cutoff Channel